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 12 <= ISPEC <= 16: xHSEQR or one of its subroutines, see IPARMQ for detailed explanation``` [in] NVALUE ``` NVALUE is INTEGER The value of the parameter specified by ISPEC.```

Definition at line 80 of file xlaenv.f.

81*
82* -- LAPACK test routine --
83* -- LAPACK is a software package provided by Univ. of Tennessee, --
84* -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
85*
86* .. Scalar Arguments ..
87 INTEGER ISPEC, NVALUE
88* ..
89*
90* =====================================================================
91*
92* .. Arrays in Common ..
93 INTEGER IPARMS( 100 )
94* ..
95* .. Common blocks ..
96 COMMON / claenv / iparms
97* ..
98* .. Save statement ..
99 SAVE / claenv /
100* ..
101* .. Executable Statements ..
102*
103 IF( ispec.GE.1 .AND. ispec.LE.16 ) THEN
104 iparms( ispec ) = nvalue
105 END IF
106*
107 RETURN
108*
109* End of XLAENV
110*