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NAME
     ilaenv - choose problem-dependent parameters

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

     CHARACTER*( * ) NAME, OPTS

     INTEGER ISPEC, N1, N2, N3, N4



     #include <sunperf.h>

     int ilaenv(int ispec, char *name, char *opts,  int  n1,  int
               n2, int n3, int 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.

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 perfor-
               mance.
               = 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  nonsym-
               metric eigenvalue routines
               = 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  reduc-
               ing  an  m  by  n  matrix  to  bidiagonal form, if
               max(m,n)/min(m,n) exceeds this value, a QR factor-
               ization  is  used  first to reduce the matrix to a
               triangular form.)
               = 7: the number of processors
               = 8: the crossover point for the multishift QR and
               QZ methods for nonsymmetric eigenvalue problems.

     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, con-
               catenated  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, N2, N3, N4
               (input) INTEGER
               Problem dimensions for the subroutine NAME;  these
               may not all be required.
               >= 0: the value  of  the  parameter  specified  by
               ISPEC
               < 0:  if ILAENV = -k, the  k-th  argument  had  an
               illegal value.

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  fol-
     lows:

         NB = ILAENV( 1, 'STRTRI', UPLO // DIAG, N, -1, -1, -1 )
         IF( NB.LE.1 ) NB = MAX( 1, N )

SAMPLE PROGRAM USING C
     #include <sunperf.h>
     main() {

       char *s1 = "dgetri", *s2 = " ";
       int nb;

       nb = ilaenv(1, s1, s2, 2, -1, -1, -1);
     }

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