ilaenv.f File Reference

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Functions/Subroutines
integer function	ilaenv (ispec, name, opts, n1, n2, n3, n4)
	ILAENV
integer function	ilaenv2stage (ispec, name, opts, n1, n2, n3, n4)
integer function	iparmq (ispec, name, opts, n, ilo, ihi, lwork)

Function/Subroutine Documentation

ilaenv2stage()

integer function ilaenv2stage	(	integer	ispec,
		character*( * )	name,
		character*( * )	opts,
		integer	n1,
		integer	n2,
		integer	n3,
		integer	n4 )

Definition at line 251 of file ilaenv.f.

*     .. Scalar Arguments ..
      CHARACTER*( * )    NAME, OPTS
      INTEGER            ISPEC, N1, N2, N3, N4
*     ..
*
*  =====================================================================
*
*     .. Local variables ..
      INTEGER            IISPEC
*     .. External Functions ..
      INTEGER            IPARAM2STAGE
      EXTERNAL           iparam2stage
*     ..
*     .. Arrays in Common ..
      INTEGER            IPARMS( 100 )
*     ..
*     .. Common blocks ..
      COMMON             / claenv / iparms
*     ..
*     .. Save statement ..
      SAVE               / claenv /
*     ..
*     .. Executable Statements ..
*
      IF(( ispec.GE.1 ) .AND. (ispec.LE.5)) THEN
*
*     1 <= ISPEC <= 5: 2stage eigenvalues SVD routines. 
*
         IF( ispec.EQ.1 ) THEN
             ilaenv2stage = iparms( 1 )
         ELSE
             iispec = 16 + ispec
             ilaenv2stage = iparam2stage( iispec, name, opts,
     $                                    n1, n2, n3, n4 ) 
         ENDIF
*
      ELSE
*
*        Invalid value for ISPEC
*
         ilaenv2stage = -1
      END IF
*
      RETURN
*
*     End of ILAENV2STAGE
*

iparmq()

integer function iparmq	(	integer	ispec,
		character, dimension( * )	name,
		character, dimension( * )	opts,
		integer	n,
		integer	ilo,
		integer	ihi,
		integer	lwork )

Definition at line 301 of file ilaenv.f.

*
      INTEGER            INMIN, INWIN, INIBL, ISHFTS, IACC22
      parameter( inmin = 12, inwin = 13, inibl = 14,
     $                   ishfts = 15, iacc22 = 16 )
      INTEGER            NMIN, K22MIN, KACMIN, NIBBLE, KNWSWP
      parameter( nmin = 11, k22min = 14, kacmin = 14,
     $                   nibble = 14, knwswp = 500 )
      REAL               TWO
      parameter( two = 2.0 )
*     ..
*     .. Scalar Arguments ..
      INTEGER            IHI, ILO, ISPEC, LWORK, N
      CHARACTER          NAME*( * ), OPTS*( * )
*     ..
*     .. Local Scalars ..
      INTEGER            NH, NS
*     ..
*     .. Intrinsic Functions ..
      INTRINSIC          log, max, mod, nint, real
*     ..
*     .. Executable Statements ..
      IF( ( ispec.EQ.ishfts ) .OR. ( ispec.EQ.inwin ) .OR.
     $    ( ispec.EQ.iacc22 ) ) THEN
*
*        ==== Set the number simultaneous shifts ====
*
         nh = ihi - ilo + 1
         ns = 2
         IF( nh.GE.30 )
     $      ns = 4
         IF( nh.GE.60 )
     $      ns = 10
         IF( nh.GE.150 )
     $      ns = max( 10, nh / nint( log( real( nh ) ) / log( two ) ) )
         IF( nh.GE.590 )
     $      ns = 64
         IF( nh.GE.3000 )
     $      ns = 128
         IF( nh.GE.6000 )
     $      ns = 256
         ns = max( 2, ns-mod( ns, 2 ) )
      END IF
*
      IF( ispec.EQ.inmin ) THEN
*
*
*        ===== Matrices of order smaller than NMIN get sent
*        .     to LAHQR, the classic double shift algorithm.
*        .     This must be at least 11. ====
*
         iparmq = nmin
*
      ELSE IF( ispec.EQ.inibl ) THEN
*
*        ==== INIBL: skip a multi-shift qr iteration and
*        .    whenever aggressive early deflation finds
*        .    at least (NIBBLE*(window size)/100) deflations. ====
*
         iparmq = nibble
*
      ELSE IF( ispec.EQ.ishfts ) THEN
*
*        ==== NSHFTS: The number of simultaneous shifts =====
*
         iparmq = ns
*
      ELSE IF( ispec.EQ.inwin ) THEN
*
*        ==== NW: deflation window size.  ====
*
         IF( nh.LE.knwswp ) THEN
            iparmq = ns
         ELSE
            iparmq = 3*ns / 2
         END IF
*
      ELSE IF( ispec.EQ.iacc22 ) THEN
*
*        ==== IACC22: Whether to accumulate reflections
*        .     before updating the far-from-diagonal elements
*        .     and whether to use 2-by-2 block structure while
*        .     doing it.  A small amount of work could be saved
*        .     by making this choice dependent also upon the
*        .     NH=IHI-ILO+1.
*
         iparmq = 0
         IF( ns.GE.kacmin )
     $      iparmq = 1
         IF( ns.GE.k22min )
     $      iparmq = 2
*
      ELSE
*        ===== invalid value of ispec =====
         iparmq = -1
*
      END IF
*
*     ==== End of IPARMQ ====
*