Provided by: liblapack-doc_3.3.1-1_all bug

NAME

       LAPACK-3  -  is called from the LAPACK routines to choose problem-dependent parameters for
       the local environment

SYNOPSIS

       INTEGER FUNCTION ILAENV( ISPEC, NAME, OPTS, N1, N2, N3, N4 )

           CHARACTER*(  * ) NAME, OPTS

           INTEGER      ISPEC, N1, N2, N3, N4

PURPOSE

       ILAENV is called from the LAPACK routines to choose problem-dependent parameters  for  the
       local environment.  See ISPEC for a description of
        the parameters.
        ILAENV returns an INTEGER
        if ILAENV >= 0: ILAENV returns the value of the parameter specified by ISPEC
        if ILAENV < 0:  if ILAENV = -k, the k-th argument had an illegal value.
        This version provides a set of parameters which should give good,
        but not optimal, performance on many of the currently available
        computers.  Users are encouraged to modify this subroutine to set
        the tuning parameters for their particular machine using the option
        and problem size information in the arguments.
        This routine will not function correctly if it is converted to all
        lower case.  Converting it to all upper case is allowed.

ARGUMENTS

        ISPEC   (input) INTEGER
                Specifies the parameter to be returned as the value of
                ILAENV.
                = 1: the optimal blocksize; if this value is 1, an unblocked
                algorithm will give the best performance.
                = 2: the minimum block size for which the block routine
                should be used; if the usable block size is less than
                this value, an unblocked routine should be used.
                = 3: the crossover point (in a block routine, for N less
                than this value, an unblocked routine should be used)
                = 4: the number of shifts, used in the nonsymmetric
                eigenvalue routines (DEPRECATED)
                = 5: the minimum column dimension for blocking to be used;
                rectangular blocks must have dimension at least k by m,
                where k is given by ILAENV(2,...) and m by ILAENV(5,...)
                = 6: the crossover point for the SVD (when reducing an m by n
                matrix to bidiagonal form, if max(m,n)/min(m,n) exceeds
                this value, a QR factorization is used first to reduce
                the matrix to a triangular form.)
                = 7: the number of processors
                = 8: the crossover point for the multishift QR method
                for nonsymmetric eigenvalue problems (DEPRECATED)
                = 9: maximum size of the subproblems at the bottom of the
                computation tree in the divide-and-conquer algorithm
                (used by xGELSD and xGESDD)
                =10: ieee NaN arithmetic can be trusted not to trap
                =11: infinity arithmetic can be trusted not to trap
                12 <= ISPEC <= 16:
                xHSEQR or one of its subroutines,
                see IPARMQ for detailed explanation

        NAME    (input) CHARACTER*(*)
                The name of the calling subroutine, in either upper case or
                lower case.

        OPTS    (input) CHARACTER*(*)
                The character options to the subroutine NAME, concatenated
                into a single character string.  For example, UPLO = 'U',
                TRANS = 'T', and DIAG = 'N' for a triangular routine would
                be specified as OPTS = 'UTN'.

        N1      (input) INTEGER
                N2      (input) INTEGER
                N3      (input) INTEGER
                N4      (input) INTEGER
                Problem dimensions for the subroutine NAME; these may not all
                be required.

FURTHER DETAILS

        The following conventions have been used when calling ILAENV from the
        LAPACK routines:
        1)  OPTS is a concatenation of all of the character options to
            subroutine NAME, in the same order that they appear in the
            argument list for NAME, even if they are not used in determining
            the value of the parameter specified by ISPEC.
        2)  The problem dimensions N1, N2, N3, N4 are specified in the order
            that they appear in the argument list for NAME.  N1 is used
            first, N2 second, and so on, and unused problem dimensions are
            passed a value of -1.
        3)  The parameter value returned by ILAENV is checked for validity in
            the calling subroutine.  For example, ILAENV is used to retrieve
            the optimal blocksize for STRTRI as follows:
            NB = ILAENV( 1, 'STRTRI', UPLO // DIAG, N, -1, -1, -1 )
            IF( NB.LE.1 ) NB = MAX( 1, N )

 LAPACK auxiliary routine (version 3.2.1)   April 2011                            ILAENV(3lapack)