Provided by: liblapack-doc_3.12.0-3build1.1_all bug

NAME

       hetrf_rk - {he,sy}trf_rk: triangular factor

SYNOPSIS

   Functions
       subroutine chetrf_rk (uplo, n, a, lda, e, ipiv, work, lwork, info)
           CHETRF_RK computes the factorization of a complex Hermitian indefinite matrix using
           the bounded Bunch-Kaufman (rook) diagonal pivoting method (BLAS3 blocked algorithm).
       subroutine csytrf_rk (uplo, n, a, lda, e, ipiv, work, lwork, info)
           CSYTRF_RK computes the factorization of a complex symmetric indefinite matrix using
           the bounded Bunch-Kaufman (rook) diagonal pivoting method (BLAS3 blocked algorithm).
       subroutine dsytrf_rk (uplo, n, a, lda, e, ipiv, work, lwork, info)
           DSYTRF_RK computes the factorization of a real symmetric indefinite matrix using the
           bounded Bunch-Kaufman (rook) diagonal pivoting method (BLAS3 blocked algorithm).
       subroutine ssytrf_rk (uplo, n, a, lda, e, ipiv, work, lwork, info)
           SSYTRF_RK computes the factorization of a real symmetric indefinite matrix using the
           bounded Bunch-Kaufman (rook) diagonal pivoting method (BLAS3 blocked algorithm).
       subroutine zhetrf_rk (uplo, n, a, lda, e, ipiv, work, lwork, info)
           ZHETRF_RK computes the factorization of a complex Hermitian indefinite matrix using
           the bounded Bunch-Kaufman (rook) diagonal pivoting method (BLAS3 blocked algorithm).
       subroutine zsytrf_rk (uplo, n, a, lda, e, ipiv, work, lwork, info)
           ZSYTRF_RK computes the factorization of a complex symmetric indefinite matrix using
           the bounded Bunch-Kaufman (rook) diagonal pivoting method (BLAS3 blocked algorithm).

Detailed Description

Function Documentation

   subroutine chetrf_rk (character uplo, integer n, complex, dimension( lda, * ) a, integer lda,
       complex, dimension( * ) e, integer, dimension( * ) ipiv, complex, dimension( * ) work,
       integer lwork, integer info)
       CHETRF_RK computes the factorization of a complex Hermitian indefinite matrix using the
       bounded Bunch-Kaufman (rook) diagonal pivoting method (BLAS3 blocked algorithm).

       Purpose:

            CHETRF_RK computes the factorization of a complex Hermitian matrix A
            using the bounded Bunch-Kaufman (rook) diagonal pivoting method:

               A = P*U*D*(U**H)*(P**T) or A = P*L*D*(L**H)*(P**T),

            where U (or L) is unit upper (or lower) triangular matrix,
            U**H (or L**H) is the conjugate of U (or L), P is a permutation
            matrix, P**T is the transpose of P, and D is Hermitian and block
            diagonal with 1-by-1 and 2-by-2 diagonal blocks.

            This is the blocked version of the algorithm, calling Level 3 BLAS.
            For more information see Further Details section.

       Parameters
           UPLO

                     UPLO is CHARACTER*1
                     Specifies whether the upper or lower triangular part of the
                     Hermitian matrix A is stored:
                     = 'U':  Upper triangular
                     = 'L':  Lower triangular

           N

                     N is INTEGER
                     The order of the matrix A.  N >= 0.

           A

                     A is COMPLEX array, dimension (LDA,N)
                     On entry, the Hermitian matrix A.
                       If UPLO = 'U': the leading N-by-N upper triangular part
                       of A contains the upper triangular part of the matrix A,
                       and the strictly lower triangular part of A is not
                       referenced.

                       If UPLO = 'L': the leading N-by-N lower triangular part
                       of A contains the lower triangular part of the matrix A,
                       and the strictly upper triangular part of A is not
                       referenced.

                     On exit, contains:
                       a) ONLY diagonal elements of the Hermitian block diagonal
                          matrix D on the diagonal of A, i.e. D(k,k) = A(k,k);
                          (superdiagonal (or subdiagonal) elements of D
                           are stored on exit in array E), and
                       b) If UPLO = 'U': factor U in the superdiagonal part of A.
                          If UPLO = 'L': factor L in the subdiagonal part of A.

           LDA

                     LDA is INTEGER
                     The leading dimension of the array A.  LDA >= max(1,N).

           E

                     E is COMPLEX array, dimension (N)
                     On exit, contains the superdiagonal (or subdiagonal)
                     elements of the Hermitian block diagonal matrix D
                     with 1-by-1 or 2-by-2 diagonal blocks, where
                     If UPLO = 'U': E(i) = D(i-1,i), i=2:N, E(1) is set to 0;
                     If UPLO = 'L': E(i) = D(i+1,i), i=1:N-1, E(N) is set to 0.

                     NOTE: For 1-by-1 diagonal block D(k), where
                     1 <= k <= N, the element E(k) is set to 0 in both
                     UPLO = 'U' or UPLO = 'L' cases.

           IPIV

                     IPIV is INTEGER array, dimension (N)
                     IPIV describes the permutation matrix P in the factorization
                     of matrix A as follows. The absolute value of IPIV(k)
                     represents the index of row and column that were
                     interchanged with the k-th row and column. The value of UPLO
                     describes the order in which the interchanges were applied.
                     Also, the sign of IPIV represents the block structure of
                     the Hermitian block diagonal matrix D with 1-by-1 or 2-by-2
                     diagonal blocks which correspond to 1 or 2 interchanges
                     at each factorization step. For more info see Further
                     Details section.

                     If UPLO = 'U',
                     ( in factorization order, k decreases from N to 1 ):
                       a) A single positive entry IPIV(k) > 0 means:
                          D(k,k) is a 1-by-1 diagonal block.
                          If IPIV(k) != k, rows and columns k and IPIV(k) were
                          interchanged in the matrix A(1:N,1:N);
                          If IPIV(k) = k, no interchange occurred.

                       b) A pair of consecutive negative entries
                          IPIV(k) < 0 and IPIV(k-1) < 0 means:
                          D(k-1:k,k-1:k) is a 2-by-2 diagonal block.
                          (NOTE: negative entries in IPIV appear ONLY in pairs).
                          1) If -IPIV(k) != k, rows and columns
                             k and -IPIV(k) were interchanged
                             in the matrix A(1:N,1:N).
                             If -IPIV(k) = k, no interchange occurred.
                          2) If -IPIV(k-1) != k-1, rows and columns
                             k-1 and -IPIV(k-1) were interchanged
                             in the matrix A(1:N,1:N).
                             If -IPIV(k-1) = k-1, no interchange occurred.

                       c) In both cases a) and b), always ABS( IPIV(k) ) <= k.

                       d) NOTE: Any entry IPIV(k) is always NONZERO on output.

                     If UPLO = 'L',
                     ( in factorization order, k increases from 1 to N ):
                       a) A single positive entry IPIV(k) > 0 means:
                          D(k,k) is a 1-by-1 diagonal block.
                          If IPIV(k) != k, rows and columns k and IPIV(k) were
                          interchanged in the matrix A(1:N,1:N).
                          If IPIV(k) = k, no interchange occurred.

                       b) A pair of consecutive negative entries
                          IPIV(k) < 0 and IPIV(k+1) < 0 means:
                          D(k:k+1,k:k+1) is a 2-by-2 diagonal block.
                          (NOTE: negative entries in IPIV appear ONLY in pairs).
                          1) If -IPIV(k) != k, rows and columns
                             k and -IPIV(k) were interchanged
                             in the matrix A(1:N,1:N).
                             If -IPIV(k) = k, no interchange occurred.
                          2) If -IPIV(k+1) != k+1, rows and columns
                             k-1 and -IPIV(k-1) were interchanged
                             in the matrix A(1:N,1:N).
                             If -IPIV(k+1) = k+1, no interchange occurred.

                       c) In both cases a) and b), always ABS( IPIV(k) ) >= k.

                       d) NOTE: Any entry IPIV(k) is always NONZERO on output.

           WORK

                     WORK is COMPLEX array, dimension ( MAX(1,LWORK) ).
                     On exit, if INFO = 0, WORK(1) returns the optimal LWORK.

           LWORK

                     LWORK is INTEGER
                     The length of WORK.  LWORK >=1.  For best performance
                     LWORK >= N*NB, where NB is the block size returned
                     by ILAENV.

                     If LWORK = -1, then a workspace query is assumed;
                     the routine only calculates the optimal size of the WORK
                     array, returns this value as the first entry of the WORK
                     array, and no error message related to LWORK is issued
                     by XERBLA.

           INFO

                     INFO is INTEGER
                     = 0: successful exit

                     < 0: If INFO = -k, the k-th argument had an illegal value

                     > 0: If INFO = k, the matrix A is singular, because:
                            If UPLO = 'U': column k in the upper
                            triangular part of A contains all zeros.
                            If UPLO = 'L': column k in the lower
                            triangular part of A contains all zeros.

                          Therefore D(k,k) is exactly zero, and superdiagonal
                          elements of column k of U (or subdiagonal elements of
                          column k of L ) are all zeros. The factorization has
                          been completed, but the block diagonal matrix D is
                          exactly singular, and division by zero will occur if
                          it is used to solve a system of equations.

                          NOTE: INFO only stores the first occurrence of
                          a singularity, any subsequent occurrence of singularity
                          is not stored in INFO even though the factorization
                          always completes.

       Author
           Univ. of Tennessee

           Univ. of California Berkeley

           Univ. of Colorado Denver

           NAG Ltd.

       Further Details:

            TODO: put correct description

       Contributors:

             December 2016,  Igor Kozachenko,
                             Computer Science Division,
                             University of California, Berkeley

             September 2007, Sven Hammarling, Nicholas J. Higham, Craig Lucas,
                             School of Mathematics,
                             University of Manchester

   subroutine csytrf_rk (character uplo, integer n, complex, dimension( lda, * ) a, integer lda,
       complex, dimension( * ) e, integer, dimension( * ) ipiv, complex, dimension( * ) work,
       integer lwork, integer info)
       CSYTRF_RK computes the factorization of a complex symmetric indefinite matrix using the
       bounded Bunch-Kaufman (rook) diagonal pivoting method (BLAS3 blocked algorithm).

       Purpose:

            CSYTRF_RK computes the factorization of a complex symmetric matrix A
            using the bounded Bunch-Kaufman (rook) diagonal pivoting method:

               A = P*U*D*(U**T)*(P**T) or A = P*L*D*(L**T)*(P**T),

            where U (or L) is unit upper (or lower) triangular matrix,
            U**T (or L**T) is the transpose of U (or L), P is a permutation
            matrix, P**T is the transpose of P, and D is symmetric and block
            diagonal with 1-by-1 and 2-by-2 diagonal blocks.

            This is the blocked version of the algorithm, calling Level 3 BLAS.
            For more information see Further Details section.

       Parameters
           UPLO

                     UPLO is CHARACTER*1
                     Specifies whether the upper or lower triangular part of the
                     symmetric matrix A is stored:
                     = 'U':  Upper triangular
                     = 'L':  Lower triangular

           N

                     N is INTEGER
                     The order of the matrix A.  N >= 0.

           A

                     A is COMPLEX array, dimension (LDA,N)
                     On entry, the symmetric matrix A.
                       If UPLO = 'U': the leading N-by-N upper triangular part
                       of A contains the upper triangular part of the matrix A,
                       and the strictly lower triangular part of A is not
                       referenced.

                       If UPLO = 'L': the leading N-by-N lower triangular part
                       of A contains the lower triangular part of the matrix A,
                       and the strictly upper triangular part of A is not
                       referenced.

                     On exit, contains:
                       a) ONLY diagonal elements of the symmetric block diagonal
                          matrix D on the diagonal of A, i.e. D(k,k) = A(k,k);
                          (superdiagonal (or subdiagonal) elements of D
                           are stored on exit in array E), and
                       b) If UPLO = 'U': factor U in the superdiagonal part of A.
                          If UPLO = 'L': factor L in the subdiagonal part of A.

           LDA

                     LDA is INTEGER
                     The leading dimension of the array A.  LDA >= max(1,N).

           E

                     E is COMPLEX array, dimension (N)
                     On exit, contains the superdiagonal (or subdiagonal)
                     elements of the symmetric block diagonal matrix D
                     with 1-by-1 or 2-by-2 diagonal blocks, where
                     If UPLO = 'U': E(i) = D(i-1,i), i=2:N, E(1) is set to 0;
                     If UPLO = 'L': E(i) = D(i+1,i), i=1:N-1, E(N) is set to 0.

                     NOTE: For 1-by-1 diagonal block D(k), where
                     1 <= k <= N, the element E(k) is set to 0 in both
                     UPLO = 'U' or UPLO = 'L' cases.

           IPIV

                     IPIV is INTEGER array, dimension (N)
                     IPIV describes the permutation matrix P in the factorization
                     of matrix A as follows. The absolute value of IPIV(k)
                     represents the index of row and column that were
                     interchanged with the k-th row and column. The value of UPLO
                     describes the order in which the interchanges were applied.
                     Also, the sign of IPIV represents the block structure of
                     the symmetric block diagonal matrix D with 1-by-1 or 2-by-2
                     diagonal blocks which correspond to 1 or 2 interchanges
                     at each factorization step. For more info see Further
                     Details section.

                     If UPLO = 'U',
                     ( in factorization order, k decreases from N to 1 ):
                       a) A single positive entry IPIV(k) > 0 means:
                          D(k,k) is a 1-by-1 diagonal block.
                          If IPIV(k) != k, rows and columns k and IPIV(k) were
                          interchanged in the matrix A(1:N,1:N);
                          If IPIV(k) = k, no interchange occurred.

                       b) A pair of consecutive negative entries
                          IPIV(k) < 0 and IPIV(k-1) < 0 means:
                          D(k-1:k,k-1:k) is a 2-by-2 diagonal block.
                          (NOTE: negative entries in IPIV appear ONLY in pairs).
                          1) If -IPIV(k) != k, rows and columns
                             k and -IPIV(k) were interchanged
                             in the matrix A(1:N,1:N).
                             If -IPIV(k) = k, no interchange occurred.
                          2) If -IPIV(k-1) != k-1, rows and columns
                             k-1 and -IPIV(k-1) were interchanged
                             in the matrix A(1:N,1:N).
                             If -IPIV(k-1) = k-1, no interchange occurred.

                       c) In both cases a) and b), always ABS( IPIV(k) ) <= k.

                       d) NOTE: Any entry IPIV(k) is always NONZERO on output.

                     If UPLO = 'L',
                     ( in factorization order, k increases from 1 to N ):
                       a) A single positive entry IPIV(k) > 0 means:
                          D(k,k) is a 1-by-1 diagonal block.
                          If IPIV(k) != k, rows and columns k and IPIV(k) were
                          interchanged in the matrix A(1:N,1:N).
                          If IPIV(k) = k, no interchange occurred.

                       b) A pair of consecutive negative entries
                          IPIV(k) < 0 and IPIV(k+1) < 0 means:
                          D(k:k+1,k:k+1) is a 2-by-2 diagonal block.
                          (NOTE: negative entries in IPIV appear ONLY in pairs).
                          1) If -IPIV(k) != k, rows and columns
                             k and -IPIV(k) were interchanged
                             in the matrix A(1:N,1:N).
                             If -IPIV(k) = k, no interchange occurred.
                          2) If -IPIV(k+1) != k+1, rows and columns
                             k-1 and -IPIV(k-1) were interchanged
                             in the matrix A(1:N,1:N).
                             If -IPIV(k+1) = k+1, no interchange occurred.

                       c) In both cases a) and b), always ABS( IPIV(k) ) >= k.

                       d) NOTE: Any entry IPIV(k) is always NONZERO on output.

           WORK

                     WORK is COMPLEX array, dimension ( MAX(1,LWORK) ).
                     On exit, if INFO = 0, WORK(1) returns the optimal LWORK.

           LWORK

                     LWORK is INTEGER
                     The length of WORK.  LWORK >=1.  For best performance
                     LWORK >= N*NB, where NB is the block size returned
                     by ILAENV.

                     If LWORK = -1, then a workspace query is assumed;
                     the routine only calculates the optimal size of the WORK
                     array, returns this value as the first entry of the WORK
                     array, and no error message related to LWORK is issued
                     by XERBLA.

           INFO

                     INFO is INTEGER
                     = 0: successful exit

                     < 0: If INFO = -k, the k-th argument had an illegal value

                     > 0: If INFO = k, the matrix A is singular, because:
                            If UPLO = 'U': column k in the upper
                            triangular part of A contains all zeros.
                            If UPLO = 'L': column k in the lower
                            triangular part of A contains all zeros.

                          Therefore D(k,k) is exactly zero, and superdiagonal
                          elements of column k of U (or subdiagonal elements of
                          column k of L ) are all zeros. The factorization has
                          been completed, but the block diagonal matrix D is
                          exactly singular, and division by zero will occur if
                          it is used to solve a system of equations.

                          NOTE: INFO only stores the first occurrence of
                          a singularity, any subsequent occurrence of singularity
                          is not stored in INFO even though the factorization
                          always completes.

       Author
           Univ. of Tennessee

           Univ. of California Berkeley

           Univ. of Colorado Denver

           NAG Ltd.

       Further Details:

            TODO: put correct description

       Contributors:

             December 2016,  Igor Kozachenko,
                             Computer Science Division,
                             University of California, Berkeley

             September 2007, Sven Hammarling, Nicholas J. Higham, Craig Lucas,
                             School of Mathematics,
                             University of Manchester

   subroutine dsytrf_rk (character uplo, integer n, double precision, dimension( lda, * ) a,
       integer lda, double precision, dimension( * ) e, integer, dimension( * ) ipiv, double
       precision, dimension( * ) work, integer lwork, integer info)
       DSYTRF_RK computes the factorization of a real symmetric indefinite matrix using the
       bounded Bunch-Kaufman (rook) diagonal pivoting method (BLAS3 blocked algorithm).

       Purpose:

            DSYTRF_RK computes the factorization of a real symmetric matrix A
            using the bounded Bunch-Kaufman (rook) diagonal pivoting method:

               A = P*U*D*(U**T)*(P**T) or A = P*L*D*(L**T)*(P**T),

            where U (or L) is unit upper (or lower) triangular matrix,
            U**T (or L**T) is the transpose of U (or L), P is a permutation
            matrix, P**T is the transpose of P, and D is symmetric and block
            diagonal with 1-by-1 and 2-by-2 diagonal blocks.

            This is the blocked version of the algorithm, calling Level 3 BLAS.
            For more information see Further Details section.

       Parameters
           UPLO

                     UPLO is CHARACTER*1
                     Specifies whether the upper or lower triangular part of the
                     symmetric matrix A is stored:
                     = 'U':  Upper triangular
                     = 'L':  Lower triangular

           N

                     N is INTEGER
                     The order of the matrix A.  N >= 0.

           A

                     A is DOUBLE PRECISION array, dimension (LDA,N)
                     On entry, the symmetric matrix A.
                       If UPLO = 'U': the leading N-by-N upper triangular part
                       of A contains the upper triangular part of the matrix A,
                       and the strictly lower triangular part of A is not
                       referenced.

                       If UPLO = 'L': the leading N-by-N lower triangular part
                       of A contains the lower triangular part of the matrix A,
                       and the strictly upper triangular part of A is not
                       referenced.

                     On exit, contains:
                       a) ONLY diagonal elements of the symmetric block diagonal
                          matrix D on the diagonal of A, i.e. D(k,k) = A(k,k);
                          (superdiagonal (or subdiagonal) elements of D
                           are stored on exit in array E), and
                       b) If UPLO = 'U': factor U in the superdiagonal part of A.
                          If UPLO = 'L': factor L in the subdiagonal part of A.

           LDA

                     LDA is INTEGER
                     The leading dimension of the array A.  LDA >= max(1,N).

           E

                     E is DOUBLE PRECISION array, dimension (N)
                     On exit, contains the superdiagonal (or subdiagonal)
                     elements of the symmetric block diagonal matrix D
                     with 1-by-1 or 2-by-2 diagonal blocks, where
                     If UPLO = 'U': E(i) = D(i-1,i), i=2:N, E(1) is set to 0;
                     If UPLO = 'L': E(i) = D(i+1,i), i=1:N-1, E(N) is set to 0.

                     NOTE: For 1-by-1 diagonal block D(k), where
                     1 <= k <= N, the element E(k) is set to 0 in both
                     UPLO = 'U' or UPLO = 'L' cases.

           IPIV

                     IPIV is INTEGER array, dimension (N)
                     IPIV describes the permutation matrix P in the factorization
                     of matrix A as follows. The absolute value of IPIV(k)
                     represents the index of row and column that were
                     interchanged with the k-th row and column. The value of UPLO
                     describes the order in which the interchanges were applied.
                     Also, the sign of IPIV represents the block structure of
                     the symmetric block diagonal matrix D with 1-by-1 or 2-by-2
                     diagonal blocks which correspond to 1 or 2 interchanges
                     at each factorization step. For more info see Further
                     Details section.

                     If UPLO = 'U',
                     ( in factorization order, k decreases from N to 1 ):
                       a) A single positive entry IPIV(k) > 0 means:
                          D(k,k) is a 1-by-1 diagonal block.
                          If IPIV(k) != k, rows and columns k and IPIV(k) were
                          interchanged in the matrix A(1:N,1:N);
                          If IPIV(k) = k, no interchange occurred.

                       b) A pair of consecutive negative entries
                          IPIV(k) < 0 and IPIV(k-1) < 0 means:
                          D(k-1:k,k-1:k) is a 2-by-2 diagonal block.
                          (NOTE: negative entries in IPIV appear ONLY in pairs).
                          1) If -IPIV(k) != k, rows and columns
                             k and -IPIV(k) were interchanged
                             in the matrix A(1:N,1:N).
                             If -IPIV(k) = k, no interchange occurred.
                          2) If -IPIV(k-1) != k-1, rows and columns
                             k-1 and -IPIV(k-1) were interchanged
                             in the matrix A(1:N,1:N).
                             If -IPIV(k-1) = k-1, no interchange occurred.

                       c) In both cases a) and b), always ABS( IPIV(k) ) <= k.

                       d) NOTE: Any entry IPIV(k) is always NONZERO on output.

                     If UPLO = 'L',
                     ( in factorization order, k increases from 1 to N ):
                       a) A single positive entry IPIV(k) > 0 means:
                          D(k,k) is a 1-by-1 diagonal block.
                          If IPIV(k) != k, rows and columns k and IPIV(k) were
                          interchanged in the matrix A(1:N,1:N).
                          If IPIV(k) = k, no interchange occurred.

                       b) A pair of consecutive negative entries
                          IPIV(k) < 0 and IPIV(k+1) < 0 means:
                          D(k:k+1,k:k+1) is a 2-by-2 diagonal block.
                          (NOTE: negative entries in IPIV appear ONLY in pairs).
                          1) If -IPIV(k) != k, rows and columns
                             k and -IPIV(k) were interchanged
                             in the matrix A(1:N,1:N).
                             If -IPIV(k) = k, no interchange occurred.
                          2) If -IPIV(k+1) != k+1, rows and columns
                             k-1 and -IPIV(k-1) were interchanged
                             in the matrix A(1:N,1:N).
                             If -IPIV(k+1) = k+1, no interchange occurred.

                       c) In both cases a) and b), always ABS( IPIV(k) ) >= k.

                       d) NOTE: Any entry IPIV(k) is always NONZERO on output.

           WORK

                     WORK is DOUBLE PRECISION array, dimension ( MAX(1,LWORK) ).
                     On exit, if INFO = 0, WORK(1) returns the optimal LWORK.

           LWORK

                     LWORK is INTEGER
                     The length of WORK.  LWORK >=1.  For best performance
                     LWORK >= N*NB, where NB is the block size returned
                     by ILAENV.

                     If LWORK = -1, then a workspace query is assumed;
                     the routine only calculates the optimal size of the WORK
                     array, returns this value as the first entry of the WORK
                     array, and no error message related to LWORK is issued
                     by XERBLA.

           INFO

                     INFO is INTEGER
                     = 0: successful exit

                     < 0: If INFO = -k, the k-th argument had an illegal value

                     > 0: If INFO = k, the matrix A is singular, because:
                            If UPLO = 'U': column k in the upper
                            triangular part of A contains all zeros.
                            If UPLO = 'L': column k in the lower
                            triangular part of A contains all zeros.

                          Therefore D(k,k) is exactly zero, and superdiagonal
                          elements of column k of U (or subdiagonal elements of
                          column k of L ) are all zeros. The factorization has
                          been completed, but the block diagonal matrix D is
                          exactly singular, and division by zero will occur if
                          it is used to solve a system of equations.

                          NOTE: INFO only stores the first occurrence of
                          a singularity, any subsequent occurrence of singularity
                          is not stored in INFO even though the factorization
                          always completes.

       Author
           Univ. of Tennessee

           Univ. of California Berkeley

           Univ. of Colorado Denver

           NAG Ltd.

       Further Details:

            TODO: put correct description

       Contributors:

             December 2016,  Igor Kozachenko,
                             Computer Science Division,
                             University of California, Berkeley

             September 2007, Sven Hammarling, Nicholas J. Higham, Craig Lucas,
                             School of Mathematics,
                             University of Manchester

   subroutine ssytrf_rk (character uplo, integer n, real, dimension( lda, * ) a, integer lda,
       real, dimension( * ) e, integer, dimension( * ) ipiv, real, dimension( * ) work, integer
       lwork, integer info)
       SSYTRF_RK computes the factorization of a real symmetric indefinite matrix using the
       bounded Bunch-Kaufman (rook) diagonal pivoting method (BLAS3 blocked algorithm).

       Purpose:

            SSYTRF_RK computes the factorization of a real symmetric matrix A
            using the bounded Bunch-Kaufman (rook) diagonal pivoting method:

               A = P*U*D*(U**T)*(P**T) or A = P*L*D*(L**T)*(P**T),

            where U (or L) is unit upper (or lower) triangular matrix,
            U**T (or L**T) is the transpose of U (or L), P is a permutation
            matrix, P**T is the transpose of P, and D is symmetric and block
            diagonal with 1-by-1 and 2-by-2 diagonal blocks.

            This is the blocked version of the algorithm, calling Level 3 BLAS.
            For more information see Further Details section.

       Parameters
           UPLO

                     UPLO is CHARACTER*1
                     Specifies whether the upper or lower triangular part of the
                     symmetric matrix A is stored:
                     = 'U':  Upper triangular
                     = 'L':  Lower triangular

           N

                     N is INTEGER
                     The order of the matrix A.  N >= 0.

           A

                     A is REAL array, dimension (LDA,N)
                     On entry, the symmetric matrix A.
                       If UPLO = 'U': the leading N-by-N upper triangular part
                       of A contains the upper triangular part of the matrix A,
                       and the strictly lower triangular part of A is not
                       referenced.

                       If UPLO = 'L': the leading N-by-N lower triangular part
                       of A contains the lower triangular part of the matrix A,
                       and the strictly upper triangular part of A is not
                       referenced.

                     On exit, contains:
                       a) ONLY diagonal elements of the symmetric block diagonal
                          matrix D on the diagonal of A, i.e. D(k,k) = A(k,k);
                          (superdiagonal (or subdiagonal) elements of D
                           are stored on exit in array E), and
                       b) If UPLO = 'U': factor U in the superdiagonal part of A.
                          If UPLO = 'L': factor L in the subdiagonal part of A.

           LDA

                     LDA is INTEGER
                     The leading dimension of the array A.  LDA >= max(1,N).

           E

                     E is REAL array, dimension (N)
                     On exit, contains the superdiagonal (or subdiagonal)
                     elements of the symmetric block diagonal matrix D
                     with 1-by-1 or 2-by-2 diagonal blocks, where
                     If UPLO = 'U': E(i) = D(i-1,i), i=2:N, E(1) is set to 0;
                     If UPLO = 'L': E(i) = D(i+1,i), i=1:N-1, E(N) is set to 0.

                     NOTE: For 1-by-1 diagonal block D(k), where
                     1 <= k <= N, the element E(k) is set to 0 in both
                     UPLO = 'U' or UPLO = 'L' cases.

           IPIV

                     IPIV is INTEGER array, dimension (N)
                     IPIV describes the permutation matrix P in the factorization
                     of matrix A as follows. The absolute value of IPIV(k)
                     represents the index of row and column that were
                     interchanged with the k-th row and column. The value of UPLO
                     describes the order in which the interchanges were applied.
                     Also, the sign of IPIV represents the block structure of
                     the symmetric block diagonal matrix D with 1-by-1 or 2-by-2
                     diagonal blocks which correspond to 1 or 2 interchanges
                     at each factorization step. For more info see Further
                     Details section.

                     If UPLO = 'U',
                     ( in factorization order, k decreases from N to 1 ):
                       a) A single positive entry IPIV(k) > 0 means:
                          D(k,k) is a 1-by-1 diagonal block.
                          If IPIV(k) != k, rows and columns k and IPIV(k) were
                          interchanged in the matrix A(1:N,1:N);
                          If IPIV(k) = k, no interchange occurred.

                       b) A pair of consecutive negative entries
                          IPIV(k) < 0 and IPIV(k-1) < 0 means:
                          D(k-1:k,k-1:k) is a 2-by-2 diagonal block.
                          (NOTE: negative entries in IPIV appear ONLY in pairs).
                          1) If -IPIV(k) != k, rows and columns
                             k and -IPIV(k) were interchanged
                             in the matrix A(1:N,1:N).
                             If -IPIV(k) = k, no interchange occurred.
                          2) If -IPIV(k-1) != k-1, rows and columns
                             k-1 and -IPIV(k-1) were interchanged
                             in the matrix A(1:N,1:N).
                             If -IPIV(k-1) = k-1, no interchange occurred.

                       c) In both cases a) and b), always ABS( IPIV(k) ) <= k.

                       d) NOTE: Any entry IPIV(k) is always NONZERO on output.

                     If UPLO = 'L',
                     ( in factorization order, k increases from 1 to N ):
                       a) A single positive entry IPIV(k) > 0 means:
                          D(k,k) is a 1-by-1 diagonal block.
                          If IPIV(k) != k, rows and columns k and IPIV(k) were
                          interchanged in the matrix A(1:N,1:N).
                          If IPIV(k) = k, no interchange occurred.

                       b) A pair of consecutive negative entries
                          IPIV(k) < 0 and IPIV(k+1) < 0 means:
                          D(k:k+1,k:k+1) is a 2-by-2 diagonal block.
                          (NOTE: negative entries in IPIV appear ONLY in pairs).
                          1) If -IPIV(k) != k, rows and columns
                             k and -IPIV(k) were interchanged
                             in the matrix A(1:N,1:N).
                             If -IPIV(k) = k, no interchange occurred.
                          2) If -IPIV(k+1) != k+1, rows and columns
                             k-1 and -IPIV(k-1) were interchanged
                             in the matrix A(1:N,1:N).
                             If -IPIV(k+1) = k+1, no interchange occurred.

                       c) In both cases a) and b), always ABS( IPIV(k) ) >= k.

                       d) NOTE: Any entry IPIV(k) is always NONZERO on output.

           WORK

                     WORK is REAL array, dimension ( MAX(1,LWORK) ).
                     On exit, if INFO = 0, WORK(1) returns the optimal LWORK.

           LWORK

                     LWORK is INTEGER
                     The length of WORK.  LWORK >=1.  For best performance
                     LWORK >= N*NB, where NB is the block size returned
                     by ILAENV.

                     If LWORK = -1, then a workspace query is assumed;
                     the routine only calculates the optimal size of the WORK
                     array, returns this value as the first entry of the WORK
                     array, and no error message related to LWORK is issued
                     by XERBLA.

           INFO

                     INFO is INTEGER
                     = 0: successful exit

                     < 0: If INFO = -k, the k-th argument had an illegal value

                     > 0: If INFO = k, the matrix A is singular, because:
                            If UPLO = 'U': column k in the upper
                            triangular part of A contains all zeros.
                            If UPLO = 'L': column k in the lower
                            triangular part of A contains all zeros.

                          Therefore D(k,k) is exactly zero, and superdiagonal
                          elements of column k of U (or subdiagonal elements of
                          column k of L ) are all zeros. The factorization has
                          been completed, but the block diagonal matrix D is
                          exactly singular, and division by zero will occur if
                          it is used to solve a system of equations.

                          NOTE: INFO only stores the first occurrence of
                          a singularity, any subsequent occurrence of singularity
                          is not stored in INFO even though the factorization
                          always completes.

       Author
           Univ. of Tennessee

           Univ. of California Berkeley

           Univ. of Colorado Denver

           NAG Ltd.

       Further Details:

            TODO: put correct description

       Contributors:

             December 2016,  Igor Kozachenko,
                             Computer Science Division,
                             University of California, Berkeley

             September 2007, Sven Hammarling, Nicholas J. Higham, Craig Lucas,
                             School of Mathematics,
                             University of Manchester

   subroutine zhetrf_rk (character uplo, integer n, complex*16, dimension( lda, * ) a, integer
       lda, complex*16, dimension( * ) e, integer, dimension( * ) ipiv, complex*16, dimension( *
       ) work, integer lwork, integer info)
       ZHETRF_RK computes the factorization of a complex Hermitian indefinite matrix using the
       bounded Bunch-Kaufman (rook) diagonal pivoting method (BLAS3 blocked algorithm).

       Purpose:

            ZHETRF_RK computes the factorization of a complex Hermitian matrix A
            using the bounded Bunch-Kaufman (rook) diagonal pivoting method:

               A = P*U*D*(U**H)*(P**T) or A = P*L*D*(L**H)*(P**T),

            where U (or L) is unit upper (or lower) triangular matrix,
            U**H (or L**H) is the conjugate of U (or L), P is a permutation
            matrix, P**T is the transpose of P, and D is Hermitian and block
            diagonal with 1-by-1 and 2-by-2 diagonal blocks.

            This is the blocked version of the algorithm, calling Level 3 BLAS.
            For more information see Further Details section.

       Parameters
           UPLO

                     UPLO is CHARACTER*1
                     Specifies whether the upper or lower triangular part of the
                     Hermitian matrix A is stored:
                     = 'U':  Upper triangular
                     = 'L':  Lower triangular

           N

                     N is INTEGER
                     The order of the matrix A.  N >= 0.

           A

                     A is COMPLEX*16 array, dimension (LDA,N)
                     On entry, the Hermitian matrix A.
                       If UPLO = 'U': the leading N-by-N upper triangular part
                       of A contains the upper triangular part of the matrix A,
                       and the strictly lower triangular part of A is not
                       referenced.

                       If UPLO = 'L': the leading N-by-N lower triangular part
                       of A contains the lower triangular part of the matrix A,
                       and the strictly upper triangular part of A is not
                       referenced.

                     On exit, contains:
                       a) ONLY diagonal elements of the Hermitian block diagonal
                          matrix D on the diagonal of A, i.e. D(k,k) = A(k,k);
                          (superdiagonal (or subdiagonal) elements of D
                           are stored on exit in array E), and
                       b) If UPLO = 'U': factor U in the superdiagonal part of A.
                          If UPLO = 'L': factor L in the subdiagonal part of A.

           LDA

                     LDA is INTEGER
                     The leading dimension of the array A.  LDA >= max(1,N).

           E

                     E is COMPLEX*16 array, dimension (N)
                     On exit, contains the superdiagonal (or subdiagonal)
                     elements of the Hermitian block diagonal matrix D
                     with 1-by-1 or 2-by-2 diagonal blocks, where
                     If UPLO = 'U': E(i) = D(i-1,i), i=2:N, E(1) is set to 0;
                     If UPLO = 'L': E(i) = D(i+1,i), i=1:N-1, E(N) is set to 0.

                     NOTE: For 1-by-1 diagonal block D(k), where
                     1 <= k <= N, the element E(k) is set to 0 in both
                     UPLO = 'U' or UPLO = 'L' cases.

           IPIV

                     IPIV is INTEGER array, dimension (N)
                     IPIV describes the permutation matrix P in the factorization
                     of matrix A as follows. The absolute value of IPIV(k)
                     represents the index of row and column that were
                     interchanged with the k-th row and column. The value of UPLO
                     describes the order in which the interchanges were applied.
                     Also, the sign of IPIV represents the block structure of
                     the Hermitian block diagonal matrix D with 1-by-1 or 2-by-2
                     diagonal blocks which correspond to 1 or 2 interchanges
                     at each factorization step. For more info see Further
                     Details section.

                     If UPLO = 'U',
                     ( in factorization order, k decreases from N to 1 ):
                       a) A single positive entry IPIV(k) > 0 means:
                          D(k,k) is a 1-by-1 diagonal block.
                          If IPIV(k) != k, rows and columns k and IPIV(k) were
                          interchanged in the matrix A(1:N,1:N);
                          If IPIV(k) = k, no interchange occurred.

                       b) A pair of consecutive negative entries
                          IPIV(k) < 0 and IPIV(k-1) < 0 means:
                          D(k-1:k,k-1:k) is a 2-by-2 diagonal block.
                          (NOTE: negative entries in IPIV appear ONLY in pairs).
                          1) If -IPIV(k) != k, rows and columns
                             k and -IPIV(k) were interchanged
                             in the matrix A(1:N,1:N).
                             If -IPIV(k) = k, no interchange occurred.
                          2) If -IPIV(k-1) != k-1, rows and columns
                             k-1 and -IPIV(k-1) were interchanged
                             in the matrix A(1:N,1:N).
                             If -IPIV(k-1) = k-1, no interchange occurred.

                       c) In both cases a) and b), always ABS( IPIV(k) ) <= k.

                       d) NOTE: Any entry IPIV(k) is always NONZERO on output.

                     If UPLO = 'L',
                     ( in factorization order, k increases from 1 to N ):
                       a) A single positive entry IPIV(k) > 0 means:
                          D(k,k) is a 1-by-1 diagonal block.
                          If IPIV(k) != k, rows and columns k and IPIV(k) were
                          interchanged in the matrix A(1:N,1:N).
                          If IPIV(k) = k, no interchange occurred.

                       b) A pair of consecutive negative entries
                          IPIV(k) < 0 and IPIV(k+1) < 0 means:
                          D(k:k+1,k:k+1) is a 2-by-2 diagonal block.
                          (NOTE: negative entries in IPIV appear ONLY in pairs).
                          1) If -IPIV(k) != k, rows and columns
                             k and -IPIV(k) were interchanged
                             in the matrix A(1:N,1:N).
                             If -IPIV(k) = k, no interchange occurred.
                          2) If -IPIV(k+1) != k+1, rows and columns
                             k-1 and -IPIV(k-1) were interchanged
                             in the matrix A(1:N,1:N).
                             If -IPIV(k+1) = k+1, no interchange occurred.

                       c) In both cases a) and b), always ABS( IPIV(k) ) >= k.

                       d) NOTE: Any entry IPIV(k) is always NONZERO on output.

           WORK

                     WORK is COMPLEX*16 array, dimension ( MAX(1,LWORK) ).
                     On exit, if INFO = 0, WORK(1) returns the optimal LWORK.

           LWORK

                     LWORK is INTEGER
                     The length of WORK.  LWORK >=1.  For best performance
                     LWORK >= N*NB, where NB is the block size returned
                     by ILAENV.

                     If LWORK = -1, then a workspace query is assumed;
                     the routine only calculates the optimal size of the WORK
                     array, returns this value as the first entry of the WORK
                     array, and no error message related to LWORK is issued
                     by XERBLA.

           INFO

                     INFO is INTEGER
                     = 0: successful exit

                     < 0: If INFO = -k, the k-th argument had an illegal value

                     > 0: If INFO = k, the matrix A is singular, because:
                            If UPLO = 'U': column k in the upper
                            triangular part of A contains all zeros.
                            If UPLO = 'L': column k in the lower
                            triangular part of A contains all zeros.

                          Therefore D(k,k) is exactly zero, and superdiagonal
                          elements of column k of U (or subdiagonal elements of
                          column k of L ) are all zeros. The factorization has
                          been completed, but the block diagonal matrix D is
                          exactly singular, and division by zero will occur if
                          it is used to solve a system of equations.

                          NOTE: INFO only stores the first occurrence of
                          a singularity, any subsequent occurrence of singularity
                          is not stored in INFO even though the factorization
                          always completes.

       Author
           Univ. of Tennessee

           Univ. of California Berkeley

           Univ. of Colorado Denver

           NAG Ltd.

       Further Details:

            TODO: put correct description

       Contributors:

             December 2016,  Igor Kozachenko,
                             Computer Science Division,
                             University of California, Berkeley

             September 2007, Sven Hammarling, Nicholas J. Higham, Craig Lucas,
                             School of Mathematics,
                             University of Manchester

   subroutine zsytrf_rk (character uplo, integer n, complex*16, dimension( lda, * ) a, integer
       lda, complex*16, dimension( * ) e, integer, dimension( * ) ipiv, complex*16, dimension( *
       ) work, integer lwork, integer info)
       ZSYTRF_RK computes the factorization of a complex symmetric indefinite matrix using the
       bounded Bunch-Kaufman (rook) diagonal pivoting method (BLAS3 blocked algorithm).

       Purpose:

            ZSYTRF_RK computes the factorization of a complex symmetric matrix A
            using the bounded Bunch-Kaufman (rook) diagonal pivoting method:

               A = P*U*D*(U**T)*(P**T) or A = P*L*D*(L**T)*(P**T),

            where U (or L) is unit upper (or lower) triangular matrix,
            U**T (or L**T) is the transpose of U (or L), P is a permutation
            matrix, P**T is the transpose of P, and D is symmetric and block
            diagonal with 1-by-1 and 2-by-2 diagonal blocks.

            This is the blocked version of the algorithm, calling Level 3 BLAS.
            For more information see Further Details section.

       Parameters
           UPLO

                     UPLO is CHARACTER*1
                     Specifies whether the upper or lower triangular part of the
                     symmetric matrix A is stored:
                     = 'U':  Upper triangular
                     = 'L':  Lower triangular

           N

                     N is INTEGER
                     The order of the matrix A.  N >= 0.

           A

                     A is COMPLEX*16 array, dimension (LDA,N)
                     On entry, the symmetric matrix A.
                       If UPLO = 'U': the leading N-by-N upper triangular part
                       of A contains the upper triangular part of the matrix A,
                       and the strictly lower triangular part of A is not
                       referenced.

                       If UPLO = 'L': the leading N-by-N lower triangular part
                       of A contains the lower triangular part of the matrix A,
                       and the strictly upper triangular part of A is not
                       referenced.

                     On exit, contains:
                       a) ONLY diagonal elements of the symmetric block diagonal
                          matrix D on the diagonal of A, i.e. D(k,k) = A(k,k);
                          (superdiagonal (or subdiagonal) elements of D
                           are stored on exit in array E), and
                       b) If UPLO = 'U': factor U in the superdiagonal part of A.
                          If UPLO = 'L': factor L in the subdiagonal part of A.

           LDA

                     LDA is INTEGER
                     The leading dimension of the array A.  LDA >= max(1,N).

           E

                     E is COMPLEX*16 array, dimension (N)
                     On exit, contains the superdiagonal (or subdiagonal)
                     elements of the symmetric block diagonal matrix D
                     with 1-by-1 or 2-by-2 diagonal blocks, where
                     If UPLO = 'U': E(i) = D(i-1,i), i=2:N, E(1) is set to 0;
                     If UPLO = 'L': E(i) = D(i+1,i), i=1:N-1, E(N) is set to 0.

                     NOTE: For 1-by-1 diagonal block D(k), where
                     1 <= k <= N, the element E(k) is set to 0 in both
                     UPLO = 'U' or UPLO = 'L' cases.

           IPIV

                     IPIV is INTEGER array, dimension (N)
                     IPIV describes the permutation matrix P in the factorization
                     of matrix A as follows. The absolute value of IPIV(k)
                     represents the index of row and column that were
                     interchanged with the k-th row and column. The value of UPLO
                     describes the order in which the interchanges were applied.
                     Also, the sign of IPIV represents the block structure of
                     the symmetric block diagonal matrix D with 1-by-1 or 2-by-2
                     diagonal blocks which correspond to 1 or 2 interchanges
                     at each factorization step. For more info see Further
                     Details section.

                     If UPLO = 'U',
                     ( in factorization order, k decreases from N to 1 ):
                       a) A single positive entry IPIV(k) > 0 means:
                          D(k,k) is a 1-by-1 diagonal block.
                          If IPIV(k) != k, rows and columns k and IPIV(k) were
                          interchanged in the matrix A(1:N,1:N);
                          If IPIV(k) = k, no interchange occurred.

                       b) A pair of consecutive negative entries
                          IPIV(k) < 0 and IPIV(k-1) < 0 means:
                          D(k-1:k,k-1:k) is a 2-by-2 diagonal block.
                          (NOTE: negative entries in IPIV appear ONLY in pairs).
                          1) If -IPIV(k) != k, rows and columns
                             k and -IPIV(k) were interchanged
                             in the matrix A(1:N,1:N).
                             If -IPIV(k) = k, no interchange occurred.
                          2) If -IPIV(k-1) != k-1, rows and columns
                             k-1 and -IPIV(k-1) were interchanged
                             in the matrix A(1:N,1:N).
                             If -IPIV(k-1) = k-1, no interchange occurred.

                       c) In both cases a) and b), always ABS( IPIV(k) ) <= k.

                       d) NOTE: Any entry IPIV(k) is always NONZERO on output.

                     If UPLO = 'L',
                     ( in factorization order, k increases from 1 to N ):
                       a) A single positive entry IPIV(k) > 0 means:
                          D(k,k) is a 1-by-1 diagonal block.
                          If IPIV(k) != k, rows and columns k and IPIV(k) were
                          interchanged in the matrix A(1:N,1:N).
                          If IPIV(k) = k, no interchange occurred.

                       b) A pair of consecutive negative entries
                          IPIV(k) < 0 and IPIV(k+1) < 0 means:
                          D(k:k+1,k:k+1) is a 2-by-2 diagonal block.
                          (NOTE: negative entries in IPIV appear ONLY in pairs).
                          1) If -IPIV(k) != k, rows and columns
                             k and -IPIV(k) were interchanged
                             in the matrix A(1:N,1:N).
                             If -IPIV(k) = k, no interchange occurred.
                          2) If -IPIV(k+1) != k+1, rows and columns
                             k-1 and -IPIV(k-1) were interchanged
                             in the matrix A(1:N,1:N).
                             If -IPIV(k+1) = k+1, no interchange occurred.

                       c) In both cases a) and b), always ABS( IPIV(k) ) >= k.

                       d) NOTE: Any entry IPIV(k) is always NONZERO on output.

           WORK

                     WORK is COMPLEX*16 array, dimension ( MAX(1,LWORK) ).
                     On exit, if INFO = 0, WORK(1) returns the optimal LWORK.

           LWORK

                     LWORK is INTEGER
                     The length of WORK.  LWORK >=1.  For best performance
                     LWORK >= N*NB, where NB is the block size returned
                     by ILAENV.

                     If LWORK = -1, then a workspace query is assumed;
                     the routine only calculates the optimal size of the WORK
                     array, returns this value as the first entry of the WORK
                     array, and no error message related to LWORK is issued
                     by XERBLA.

           INFO

                     INFO is INTEGER
                     = 0: successful exit

                     < 0: If INFO = -k, the k-th argument had an illegal value

                     > 0: If INFO = k, the matrix A is singular, because:
                            If UPLO = 'U': column k in the upper
                            triangular part of A contains all zeros.
                            If UPLO = 'L': column k in the lower
                            triangular part of A contains all zeros.

                          Therefore D(k,k) is exactly zero, and superdiagonal
                          elements of column k of U (or subdiagonal elements of
                          column k of L ) are all zeros. The factorization has
                          been completed, but the block diagonal matrix D is
                          exactly singular, and division by zero will occur if
                          it is used to solve a system of equations.

                          NOTE: INFO only stores the first occurrence of
                          a singularity, any subsequent occurrence of singularity
                          is not stored in INFO even though the factorization
                          always completes.

       Author
           Univ. of Tennessee

           Univ. of California Berkeley

           Univ. of Colorado Denver

           NAG Ltd.

       Further Details:

            TODO: put correct description

       Contributors:

             December 2016,  Igor Kozachenko,
                             Computer Science Division,
                             University of California, Berkeley

             September 2007, Sven Hammarling, Nicholas J. Higham, Craig Lucas,
                             School of Mathematics,
                             University of Manchester

Author

       Generated automatically by Doxygen for LAPACK from the source code.