ilaenv.f

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*> \brief \b ILAENV
*
*  =========== DOCUMENTATION ===========
*
* Online html documentation available at
*            http://www.netlib.org/lapack/explore-html/
*
*> \htmlonly
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*> \endhtmlonly
*
*  Definition:
*  ===========
*
*       INTEGER FUNCTION ILAENV( ISPEC, NAME, OPTS, N1, N2, N3, N4 )
*
*       .. Scalar Arguments ..
*       CHARACTER*( * )    NAME, OPTS
*       INTEGER            ISPEC, N1, N2, N3, N4
*       ..
*
*
*> \par Purpose:
*  =============
*>
*> \verbatim
*>
*> 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.
*> \endverbatim
*
*  Arguments:
*  ==========
*
*> \param[in] ISPEC
*> \verbatim
*>          ISPEC is 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 infinity and NaN arithmetic can be trusted not to trap
*>          =11: infinity arithmetic can be trusted not to trap
*>          12 <= ISPEC <= 17:
*>               xHSEQR or related subroutines,
*>               see IPARMQ for detailed explanation
*> \endverbatim
*>
*> \param[in] NAME
*> \verbatim
*>          NAME is CHARACTER*(*)
*>          The name of the calling subroutine, in either upper case or
*>          lower case.
*> \endverbatim
*>
*> \param[in] OPTS
*> \verbatim
*>          OPTS is 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'.
*> \endverbatim
*>
*> \param[in] N1
*> \verbatim
*>          N1 is INTEGER
*> \endverbatim
*>
*> \param[in] N2
*> \verbatim
*>          N2 is INTEGER
*> \endverbatim
*>
*> \param[in] N3
*> \verbatim
*>          N3 is INTEGER
*> \endverbatim
*>
*> \param[in] N4
*> \verbatim
*>          N4 is INTEGER
*>          Problem dimensions for the subroutine NAME; these may not all
*>          be required.
*> \endverbatim
*
*  Authors:
*  ========
*
*> \author Univ. of Tennessee
*> \author Univ. of California Berkeley
*> \author Univ. of Colorado Denver
*> \author NAG Ltd.
*
*> \ingroup OTHERauxiliary
*
*> \par Further Details:
*  =====================
*>
*> \verbatim
*>
*>  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 )
*> \endverbatim
*>
*  =====================================================================
      INTEGER FUNCTION ilaenv( ISPEC, NAME, OPTS, N1, N2, N3, N4 )
*
*  -- LAPACK auxiliary routine --
*  -- LAPACK is a software package provided by Univ. of Tennessee,    --
*  -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
*
*     .. Scalar Arguments ..
      CHARACTER*( * )    name, opts
      INTEGER            ISPEC, n1, n2, n3, n4
*     ..
*
*  =====================================================================
*
*     .. Local Scalars ..
      INTEGER            i, IC, iz, nb, nbmin, nx
      LOGICAL            cname, sname, twostage
      CHARACTER          C1*1, c2*2, c4*2, c3*3, subnam*16
*     ..
*     .. Intrinsic Functions ..
      INTRINSIC          char, ichar, int, min, real
*     ..
*     .. External Functions ..
      INTEGER            ieeeck, iparmq, iparam2stage
      EXTERNAL           ieeeck, iparmq, iparam2stage
*     ..
*     .. Executable Statements ..
*
      GO TO ( 10, 10, 10, 80, 90, 100, 110, 120,
     $        130, 140, 150, 160, 160, 160, 160, 160, 160)ispec
*
*     Invalid value for ISPEC
*
      ilaenv = -1
      RETURN
*
   10 CONTINUE
*
*     Convert NAME to upper case if the first character is lower case.
*
      ilaenv = 1
      subnam = name
      ic = ichar( subnam( 1: 1 ) )
      iz = ichar( 'Z' )
      IF( iz.EQ.90 .OR. iz.EQ.122 ) THEN
*
*        ASCII character set
*
         IF( ic.GE.97 .AND. ic.LE.122 ) THEN
            subnam( 1: 1 ) = char( ic-32 )
            DO 20 i = 2, 6
               ic = ichar( subnam( i: i ) )
               IF( ic.GE.97 .AND. ic.LE.122 )
     $            subnam( i: i ) = char( ic-32 )
   20       CONTINUE
         END IF
*
      ELSE IF( iz.EQ.233 .OR. iz.EQ.169 ) THEN
*
*        EBCDIC character set
*
         IF( ( ic.GE.129 .AND. ic.LE.137 ) .OR.
     $       ( ic.GE.145 .AND. ic.LE.153 ) .OR.
     $       ( ic.GE.162 .AND. ic.LE.169 ) ) THEN
            subnam( 1: 1 ) = char( ic+64 )
            DO 30 i = 2, 6
               ic = ichar( subnam( i: i ) )
               IF( ( ic.GE.129 .AND. ic.LE.137 ) .OR.
     $             ( ic.GE.145 .AND. ic.LE.153 ) .OR.
     $             ( ic.GE.162 .AND. ic.LE.169 ) )subnam( i:
     $             i ) = char( ic+64 )
   30       CONTINUE
         END IF
*
      ELSE IF( iz.EQ.218 .OR. iz.EQ.250 ) THEN
*
*        Prime machines:  ASCII+128
*
         IF( ic.GE.225 .AND. ic.LE.250 ) THEN
            subnam( 1: 1 ) = char( ic-32 )
            DO 40 i = 2, 6
               ic = ichar( subnam( i: i ) )
               IF( ic.GE.225 .AND. ic.LE.250 )
     $            subnam( i: i ) = char( ic-32 )
   40       CONTINUE
         END IF
      END IF
*
      c1 = subnam( 1: 1 )
      sname = c1.EQ.'S' .OR. c1.EQ.'D'
      cname = c1.EQ.'C' .OR. c1.EQ.'Z'
      IF( .NOT.( cname .OR. sname ) )
     $   RETURN
      c2 = subnam( 2: 3 )
      c3 = subnam( 4: 6 )
      c4 = c3( 2: 3 )
      twostage = len( subnam ).GE.11
     $           .AND. subnam( 11: 11 ).EQ.'2'
*
      GO TO ( 50, 60, 70 )ISPEC
*
   50 CONTINUE
*
*     ISPEC = 1:  block size
*
*     In these examples, separate code is provided for setting NB for
*     real and complex.  We assume that NB will take the same value in
*     single or double precision.
*
      NB = 1
*
.EQ.      IF( SUBNAM(2:6)'laorh' ) THEN
*
*        This is for *LAORHR_GETRFNP routine
*
         IF( SNAME ) THEN
             NB = 32
         ELSE
             NB = 32
         END IF
.EQ.      ELSE IF( C2'ge' ) THEN
.EQ.         IF( C3'trf' ) THEN
            IF( SNAME ) THEN
               NB = 64
            ELSE
               NB = 64
            END IF
.EQ.         ELSE IF( C3'qrf.OR..EQ.'  C3'rqf.OR..EQ.'  C3'lqf.OR.' 
.EQ.     $            C3'qlf' ) THEN
            IF( SNAME ) THEN
               NB = 32
            ELSE
               NB = 32
            END IF
.EQ.         ELSE IF( C3'qr ') THEN
.EQ.            IF( N3  1) THEN
               IF( SNAME ) THEN
*     M*N
.LE..OR..LE.                  IF ((N1*N2131072)(N18192)) THEN
                     NB = N1
                  ELSE
                     NB = 32768/N2
                  END IF
               ELSE
.LE..OR..LE.                  IF ((N1*N2131072)(N18192)) THEN
                     NB = N1
                  ELSE
                     NB = 32768/N2
                  END IF
               END IF
            ELSE
               IF( SNAME ) THEN
                  NB = 1
               ELSE
                  NB = 1
               END IF
            END IF
.EQ.         ELSE IF( C3'lq ') THEN
.EQ.            IF( N3  2) THEN
               IF( SNAME ) THEN
*     M*N
.LE..OR..LE.                  IF ((N1*N2131072)(N18192)) THEN
                     NB = N1
                  ELSE
                     NB = 32768/N2
                  END IF
               ELSE
.LE..OR..LE.                  IF ((N1*N2131072)(N18192)) THEN
                     NB = N1
                  ELSE
                     NB = 32768/N2
                  END IF
               END IF
            ELSE
               IF( SNAME ) THEN
                  NB = 1
               ELSE
                  NB = 1
               END IF
            END IF
.EQ.         ELSE IF( C3'hrd' ) THEN
            IF( SNAME ) THEN
               NB = 32
            ELSE
               NB = 32
            END IF
.EQ.         ELSE IF( C3'brd' ) THEN
            IF( SNAME ) THEN
               NB = 32
            ELSE
               NB = 32
            END IF
.EQ.         ELSE IF( C3'tri' ) THEN
            IF( SNAME ) THEN
               NB = 64
            ELSE
               NB = 64
            END IF
         END IF
.EQ.      ELSE IF( C2'po' ) THEN
.EQ.         IF( C3'trf' ) THEN
            IF( SNAME ) THEN
               NB = 64
            ELSE
               NB = 64
            END IF
         END IF
.EQ.      ELSE IF( C2'sy' ) THEN
.EQ.         IF( C3'trf' ) THEN
            IF( SNAME ) THEN
               IF( TWOSTAGE ) THEN
                  NB = 192
               ELSE
                  NB = 64
               END IF
            ELSE
               IF( TWOSTAGE ) THEN
                  NB = 192
               ELSE
                  NB = 64
               END IF
            END IF
.AND..EQ.         ELSE IF( SNAME  C3'trd' ) THEN
            NB = 32
.AND..EQ.         ELSE IF( SNAME  C3'gst' ) THEN
            NB = 64
         END IF
.AND..EQ.      ELSE IF( CNAME  C2'he' ) THEN
.EQ.         IF( C3'trf' ) THEN
            IF( TWOSTAGE ) THEN
               NB = 192
            ELSE
               NB = 64
            END IF
.EQ.         ELSE IF( C3'trd' ) THEN
            NB = 32
.EQ.         ELSE IF( C3'gst' ) THEN
            NB = 64
         END IF
.AND..EQ.      ELSE IF( SNAME  C2'or' ) THEN
.EQ.         IF( C3( 1: 1 )'g' ) THEN
.EQ.            IF( C4'qr.OR..EQ.'  C4'rq.OR..EQ.'  C4'lq.OR..EQ.'  C4
     $          'ql.OR..EQ.'  C4'hr.OR..EQ.'  C4'tr.OR..EQ.'  C4'br' )
     $           THEN
               NB = 32
            END IF
.EQ.         ELSE IF( C3( 1: 1 )'m' ) THEN
.EQ.            IF( C4'qr.OR..EQ.'  C4'rq.OR..EQ.'  C4'lq.OR..EQ.'  C4
     $          'ql' .OR. c4.EQ.'HR' .OR. c4.EQ.'TR' .OR. c4.EQ.'BR' )
     $           THEN
               nb = 32
            END IF
         END IF
      ELSE IF( cname .AND. c2.EQ.'UN' ) THEN
         IF( c3( 1: 1 ).EQ.'G' ) THEN
            IF( c4.EQ.'QR' .OR. c4.EQ.'rq.OR..EQ.'  C4'lq.OR..EQ.'  C4
     $          'ql.OR..EQ.'  C4'hr.OR..EQ.'  C4'tr' .OR. c4.EQ.'BR' )
     $           THEN
               nb = 32
            END IF
         ELSE IF( c3( 1: 1 ).EQ.'M' ) THEN
            IF( c4.EQ.'QR' .OR. c4.EQ.'RQ' .OR. c4.EQ.'LQ' .OR. c4.EQ.
     $          'QL' .OR. c4.EQ.'HR' .OR. c4.EQ.'TR' .OR. c4.EQ.'BR' )
     $           THEN
               nb = 32
            END IF
         END IF
      ELSE IF( c2.EQ.'GB' ) THEN
         IF( c3.EQ.'TRF' ) THEN
            IF( sname ) THEN
               IF( n4.LE.64 ) THEN
                  nb = 1
               ELSE
                  nb = 32
               END IF
            ELSE
               IF( n4.LE.64 ) THEN
                  nb = 1
               ELSE
                  nb = 32
               END IF
            END IF
         END IF
      ELSE IF( c2.EQ.'PB' ) THEN
         IF( c3.EQ.'TRF' ) THEN
            IF( sname ) THEN
               IF( n2.LE.64 ) THEN
                  nb = 1
               ELSE
                  nb = 32
               END IF
            ELSE
               IF( n2.LE.64 ) THEN
                  nb = 1
               ELSE
                  nb = 32
               END IF
            END IF
         END IF
      ELSE IF( c2.EQ.'TR' ) THEN
         IF( c3.EQ.'TRI' ) THEN
            IF( sname ) THEN
               nb = 64
            ELSE
               nb = 64
            END IF
         ELSE IF ( c3.EQ.'EVC' ) THEN
            IF( sname ) THEN
               nb = 64
            ELSE
               nb = 64
            END IF
         END IF
      ELSE IF( c2.EQ.'LA' ) THEN
         IF( c3.EQ.'UUM' ) THEN
            IF( sname ) THEN
               nb = 64
            ELSE
               nb = 64
            END IF
         END IF
      ELSE IF( sname .AND. c2.EQ.'ST' ) THEN
         IF( c3.EQ.'EBZ' ) THEN
            nb = 1
         END IF
      ELSE IF( c2.EQ.'GG' ) THEN
         nb = 32
         IF( c3.EQ.'HD3' ) THEN
            IF( sname ) THEN
               nb = 32
            ELSE
               nb = 32
            END IF
         END IF
      END IF
      ilaenv = nb
      RETURN
*
   60 CONTINUE
*
*     ISPEC = 2:  minimum block size
*
      nbmin = 2
      IF( c2.EQ.'GE' ) THEN
         IF( c3.EQ.'QRF' .OR. c3.EQ.'rqf.OR..EQ.'  C3'lqf.OR..EQ.'  C3
     $       'qlf' ) THEN
            IF( SNAME ) THEN
               NBMIN = 2
            ELSE
               NBMIN = 2
            END IF
.EQ.         ELSE IF( C3'hrd' ) THEN
            IF( SNAME ) THEN
               NBMIN = 2
            ELSE
               NBMIN = 2
            END IF
.EQ.         ELSE IF( C3'brd' ) THEN
            IF( SNAME ) THEN
               NBMIN = 2
            ELSE
               NBMIN = 2
            END IF
.EQ.         ELSE IF( C3'tri' ) THEN
            IF( SNAME ) THEN
               NBMIN = 2
            ELSE
               NBMIN = 2
            END IF
         END IF
.EQ.      ELSE IF( C2'sy' ) THEN
.EQ.         IF( C3'trf' ) THEN
            IF( SNAME ) THEN
               NBMIN = 8
            ELSE
               NBMIN = 8
            END IF
.AND..EQ.         ELSE IF( SNAME  C3'trd' ) THEN
            NBMIN = 2
         END IF
.AND..EQ.      ELSE IF( CNAME  C2'he' ) THEN
.EQ.         IF( C3'trd' ) THEN
            NBMIN = 2
         END IF
.AND..EQ.      ELSE IF( SNAME  C2'or' ) THEN
         IF( c3( 1: 1 ).EQ.'G' ) THEN
            IF( c4.EQ.'QR' .OR. c4.EQ.'RQ' .OR. c4.EQ.'LQ' .OR. c4.EQ.
     $          'QL' .OR. c4.EQ.'HR' .OR. c4.EQ.'TR' .OR. c4.EQ.'BR' )
     $           THEN
               nbmin = 2
            END IF
         ELSE IF( c3( 1: 1 ).EQ.'M' ) THEN
            IF( c4.EQ.'QR' .OR. c4.EQ.'RQ' .OR. c4.EQ.'LQ' .OR. c4.EQ.
     $          'QL' .OR. c4.EQ.'HR' .OR. c4.EQ.'TR' .OR. c4.EQ.'BR' )
     $           THEN
               nbmin = 2
            END IF
         END IF
      ELSE IF( cname .AND. c2.EQ.'UN' ) THEN
         IF( c3( 1: 1 ).EQ.'g' ) THEN
.EQ.            IF( C4'qr.OR..EQ.'  C4'rq.OR..EQ.'  C4'lq.OR..EQ.'  C4
     $          'ql.OR..EQ.'  C4'hr.OR..EQ.'  C4'tr.OR..EQ.'  C4'br' )
     $           THEN
               NBMIN = 2
            END IF
.EQ.         ELSE IF( C3( 1: 1 )'m' ) THEN
.EQ.            IF( C4'qr.OR..EQ.'  C4'rq.OR..EQ.'  C4'lq.OR..EQ.'  C4
     $          'ql.OR..EQ.'  C4'hr.OR..EQ.'  C4'tr.OR..EQ.'  C4'br' )
     $           THEN
               NBMIN = 2
            END IF
         END IF
.EQ.      ELSE IF( C2'gg' ) THEN
         NBMIN = 2
.EQ.         IF( C3'hd3' ) THEN
            NBMIN = 2
         END IF
      END IF
      ILAENV = NBMIN
      RETURN
*
   70 CONTINUE
*
*     ISPEC = 3:  crossover point
*
      NX = 0
.EQ.      IF( C2'ge' ) THEN
.EQ.         IF( C3'qrf.OR..EQ.'  C3'rqf.OR..EQ.'  C3'lqf.OR..EQ.'  C3
     $       'qlf' ) THEN
            IF( SNAME ) THEN
               NX = 128
            ELSE
               NX = 128
            END IF
.EQ.         ELSE IF( C3'hrd' ) THEN
            IF( SNAME ) THEN
               NX = 128
            ELSE
               NX = 128
            END IF
.EQ.         ELSE IF( C3'brd' ) THEN
            IF( SNAME ) THEN
               NX = 128
            ELSE
               NX = 128
            END IF
         END IF
.EQ.      ELSE IF( C2'sy' ) THEN
.AND..EQ.         IF( SNAME  C3'trd' ) THEN
            NX = 32
         END IF
.AND..EQ.      ELSE IF( CNAME  C2'he' ) THEN
.EQ.         IF( C3'trd' ) THEN
            NX = 32
         END IF
.AND..EQ.      ELSE IF( SNAME  C2'or' ) THEN
.EQ.         IF( C3( 1: 1 )'g' ) THEN
.EQ.            IF( C4'qr.OR..EQ.'  C4'rq.OR..EQ.'  C4'lq.OR..EQ.'  C4
     $          'ql.OR..EQ.'  C4'hr.OR..EQ.'  C4'tr.OR..EQ.'  C4'br' )
     $           THEN
               NX = 128
            END IF
         END IF
.AND..EQ.      ELSE IF( CNAME  C2'un' ) THEN
.EQ.         IF( C3( 1: 1 )'g' ) THEN
.EQ.            IF( C4'qr.OR..EQ.'  C4'rq.OR..EQ.'  C4'lq.OR..EQ.'  C4
     $          'ql.OR..EQ.'  C4'hr.OR..EQ.'  C4'tr.OR..EQ.'  C4'br' )
     $           THEN
               NX = 128
            END IF
         END IF
.EQ.      ELSE IF( C2'gg' ) THEN
         NX = 128
.EQ.         IF( C3'hd3' ) THEN
            NX = 128
         END IF
      END IF
      ILAENV = NX
      RETURN
*
   80 CONTINUE
*
*     ISPEC = 4:  number of shifts (used by xHSEQR)
*
      ILAENV = 6
      RETURN
*
   90 CONTINUE
*
*     ISPEC = 5:  minimum column dimension (not used)
*
      ILAENV = 2
      RETURN
*
  100 CONTINUE
*
*     ISPEC = 6:  crossover point for SVD (used by xGELSS and xGESVD)
*
      ILAENV = INT( REAL( MIN( N1, N2 ) )*1.6E0 )
      RETURN
*
  110 CONTINUE
*
*     ISPEC = 7:  number of processors (not used)
*
      ILAENV = 1
      RETURN
*
  120 CONTINUE
*
*     ISPEC = 8:  crossover point for multishift (used by xHSEQR)
*
      ILAENV = 50
      RETURN
*
  130 CONTINUE
*
*     ISPEC = 9:  maximum size of the subproblems at the bottom of the
*                 computation tree in the divide-and-conquer algorithm
*                 (used by xGELSD and xGESDD)
*
      ILAENV = 25
      RETURN
*
  140 CONTINUE
*
*     ISPEC = 10: ieee and infinity NaN arithmetic can be trusted not to trap
*
*     ILAENV = 0
      ILAENV = 1
.EQ.      IF( ILAENV1 ) THEN
         ILAENV = IEEECK( 1, 0.0, 1.0 )
      END IF
      RETURN
*
  150 CONTINUE
*
*     ISPEC = 11: ieee infinity arithmetic can be trusted not to trap
*
*     ILAENV = 0
      ILAENV = 1
.EQ.      IF( ILAENV1 ) THEN
         ILAENV = IEEECK( 0, 0.0, 1.0 )
      END IF
      RETURN
*
  160 CONTINUE
*
*     12 <= ISPEC <= 17: xHSEQR or related subroutines.
*
      ILAENV = IPARMQ( ISPEC, NAME, OPTS, N1, N2, N3, N4 )
      RETURN
*
*     End of ILAENV
*
      END