Provided by: scalapack-doc_1.5-10_all

**NAME**

DDTTRSV - solve one of the systems of equations L * X = B, L**T * X = B, or L**H * X = B,

**SYNOPSIS**

SUBROUTINE DDTTRSV( UPLO, TRANS, N, NRHS, DL, D, DU, B, LDB, INFO ) CHARACTER UPLO, TRANS INTEGER INFO, LDB, N, NRHS DOUBLE PRECISION B( LDB, * ), D( * ), DL( * ), DU( * )

**PURPOSE**

DDTTRSV solves one of the systems of equations L * X = B, L**T * X = B, or L**H * X = B, U * X = B, U**T * X = B, or U**H * X = B, with factors of the tridiagonal matrix A from the LU factorization computed by DDTTRF.

**ARGUMENTS**

UPLO (input) CHARACTER*1 Specifies whether to solve with L or U. TRANS (input) CHARACTER Specifies the form of the system of equations: = 'N': A * X = B (No transpose) = 'T': A**T * X = B (Transpose) = 'C': A**H * X = B (Conjugate transpose) N (input) INTEGER The order of the matrix A. N >= 0. NRHS (input) INTEGER The number of right hand sides, i.e., the number of columns of the matrix B. NRHS >= 0. DL (input) COMPLEX array, dimension (N-1) The (n-1) multipliers that define the matrix L from the LU factorization of A. D (input) COMPLEX array, dimension (N) The n diagonal elements of the upper triangular matrix U from the LU factorization of A. DU (input) COMPLEX array, dimension (N-1) The (n-1) elements of the first superdiagonal of U. B (input/output) COMPLEX array, dimension (LDB,NRHS) On entry, the right hand side matrix B. On exit, B is overwritten by the solution matrix X. LDB (input) INTEGER The leading dimension of the array B. LDB >= max(1,N). INFO (output) INTEGER = 0: successful exit < 0: if INFO = -i, the i-th argument had an illegal value