 LAPACK  3.10.1 LAPACK: Linear Algebra PACKage

## ◆ xlaenv()

 subroutine xlaenv ( integer ISPEC, integer NVALUE )

XLAENV

Purpose:
``` XLAENV sets certain machine- and problem-dependent quantities
which will later be retrieved by ILAENV.```
Parameters
 [in] ISPEC ``` ISPEC is 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``` [in] NVALUE ``` NVALUE is INTEGER The value of the parameter specified by ISPEC.```

Definition at line 77 of file xlaenv.f.

78 *
79 * -- LAPACK test routine --
80 * -- LAPACK is a software package provided by Univ. of Tennessee, --
81 * -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
82 *
83 * .. Scalar Arguments ..
84  INTEGER ISPEC, NVALUE
85 * ..
86 *
87 * =====================================================================
88 *
89 * .. Arrays in Common ..
90  INTEGER IPARMS( 100 )
91 * ..
92 * .. Common blocks ..
93  COMMON / claenv / iparms
94 * ..
95 * .. Save statement ..
96  SAVE / claenv /
97 * ..
98 * .. Executable Statements ..
99 *
100  IF( ispec.GE.1 .AND. ispec.LE.9 ) THEN
101  iparms( ispec ) = nvalue
102  END IF
103 *
104  RETURN
105 *
106 * End of XLAENV
107 *