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SUBROUTINE XLAENV( ISPEC, NVALUE )
* * -- LAPACK auxiliary routine (version 3.1) -- * Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd.. * November 2006 * * .. Scalar Arguments .. INTEGER ISPEC, NVALUE * .. * * Purpose * ======= * * XLAENV sets certain machine- and problem-dependent quantities * which will later be retrieved by ILAENV. * * Arguments * ========= * * ISPEC (input) INTEGER * Specifies the parameter to be set in the COMMON array IPARMS. * = 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: another 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 * (used by xGELSD and xGESDD) * =10: ieee NaN arithmetic can be trusted not to trap * =11: infinity arithmetic can be trusted not to trap * * NVALUE (input) INTEGER * The value of the parameter specified by ISPEC. * * ===================================================================== * * .. Arrays in Common .. INTEGER IPARMS( 100 ) * .. * .. Common blocks .. COMMON / CLAENV / IPARMS * .. * .. Save statement .. SAVE / CLAENV / * .. * .. Executable Statements .. * IF( ISPEC.GE.1 .AND. ISPEC.LE.9 ) THEN IPARMS( ISPEC ) = NVALUE END IF * RETURN * * End of XLAENV * END |