LAPACK 3.11.0 LAPACK: Linear Algebra PACKage
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## ◆ 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*