*> \brief \b ILAENV * * =========== DOCUMENTATION =========== * * Online html documentation available at * http://www.netlib.org/lapack/explore-html/ * * 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 returns problem-dependent parameters for the local *> environment. See ISPEC for a description of the parameters. *> *> In this version, the problem-dependent parameters are contained in *> the integer array IPARMS in the common block CLAENV and the value *> with index ISPEC is copied to ILAENV. This version of ILAENV is *> to be used in conjunction with XLAENV in TESTING and TIMING. *> \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 *> = 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 and QZ methods *> for nonsymmetric eigenvalue problems. *> = 9: maximum size of the subproblems at the bottom of the *> computation tree in the divide-and-conquer algorithm *> =10: ieee NaN arithmetic can be trusted not to trap *> =11: infinity arithmetic can be trusted not to trap *> *> Other specifications (up to 100) can be added later. *> \endverbatim *> *> \param[in] NAME *> \verbatim *> NAME is CHARACTER*(*) *> The name of the calling subroutine. *> \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 *> *> \return ILAENV *> \verbatim *> ILAENV is INTEGER *> >= 0: the value of the parameter specified by ISPEC *> < 0: if ILAENV = -k, the k-th argument had an illegal value. *> \endverbatim * * Authors: * ======== * *> \author Univ. of Tennessee *> \author Univ. of California Berkeley *> \author Univ. of Colorado Denver *> \author NAG Ltd. * *> \date November 2011 * *> \ingroup aux_lin * *> \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 test routine (version 3.4.0) -- * -- LAPACK is a software package provided by Univ. of Tennessee, -- * -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..-- * November 2011 * * .. Scalar Arguments .. CHARACTER*( * ) NAME, OPTS INTEGER ISPEC, N1, N2, N3, N4 * .. * * ===================================================================== * * .. Intrinsic Functions .. INTRINSIC INT, MIN, REAL * .. * .. External Functions .. INTEGER IEEECK EXTERNAL IEEECK * .. * .. 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 * * Return a value from the common block. * ILAENV = IPARMS( ISPEC ) * ELSE IF( ISPEC.EQ.6 ) THEN * * Compute SVD crossover point. * ILAENV = INT( REAL( MIN( N1, N2 ) )*1.6E0 ) * ELSE IF( ISPEC.GE.7 .AND. ISPEC.LE.9 ) THEN * * Return a value from the common block. * ILAENV = IPARMS( ISPEC ) * ELSE IF( ISPEC.EQ.10 ) THEN * * IEEE NaN arithmetic can be trusted not to trap * C ILAENV = 0 ILAENV = 1 IF( ILAENV.EQ.1 ) THEN ILAENV = IEEECK( 1, 0.0, 1.0 ) END IF * ELSE IF( ISPEC.EQ.11 ) THEN * * Infinity arithmetic can be trusted not to trap * C ILAENV = 0 ILAENV = 1 IF( ILAENV.EQ.1 ) THEN ILAENV = IEEECK( 0, 0.0, 1.0 ) END IF * ELSE * * Invalid value for ISPEC * ILAENV = -1 END IF * RETURN * * End of ILAENV * END