NAME

SYNOPSIS

  INTEGER FUNCTION ILAENV( ISPEC, NAME, OPTS, N1, N2, N3, N4)
  CHARACTER * 1 NAME, OPTS
  INTEGER ISPEC, N1, N2, N3, N4
 
  INTEGER*8 FUNCTION ILAENV_64( ISPEC, NAME, OPTS, N1, N2, N3, N4)
  CHARACTER * 1 NAME, OPTS
  INTEGER*8 ISPEC, N1, N2, N3, N4
 

F95 INTERFACE

  INTEGER FUNCTION ILAENV( ISPEC, NAME, OPTS, N1, N2, N3, N4)
  CHARACTER(LEN=1) :: NAME, OPTS
  INTEGER :: ISPEC, N1, N2, N3, N4
 
  INTEGER(8) FUNCTION ILAENV_64( ISPEC, NAME, OPTS, N1, N2, N3, N4)
  CHARACTER(LEN=1) :: NAME, OPTS
  INTEGER(8) :: ISPEC, N1, N2, N3, N4
 

C INTERFACE

int ilaenv(int ispec, char name, char opts, int n1, int n2, int n3, int n4);

long ilaenv_64(long ispec, char name, char opts, long n1, long n2, long n3, long n4);

PURPOSE

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)

Specifies the parameter to be returned as the value of ILAENV.

* NAME (input)

The name of the calling subroutine, in either upper case or lower case.

* OPTS (input)

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

N1, N2, N3, N4 are 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.

< 0: if ILAENV = -k, the k-th argument had an illegal value.

.SH 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 )