1TSTIEE ‐ called from the LAPACK routines to choose problem‐depen‐
2dent parameters for the local environment PROGRAM MAIN
3 INTEGER ILAENV
4 EXTERNAL ILAENV
5 INTEGER IEEEOK
6 WRITE( 6, FMT = * ) 'We are about to check whether infinity
7arithmetic'
8 WRITE( 6, FMT = * )'can be trusted. If this test hangs, set'
9 WRITE( 6, FMT = * ) 'ILAENV = 0 for ISPEC = 10 in LA‐
10PACK/SRC/ilaenv.f'
11 IEEEOK = ILAENV( 10, 'ILAENV', 'N', 1, 2, 3, 4 )
12 WRITE( 6, FMT = * )
13 IF( IEEEOK.EQ.0 ) THEN
14 WRITE( 6, FMT = * ) 'Infinity arithmetic did not perform per
15the ieee spec'
16 ELSE
17 WRITE( 6, FMT = * ) 'Infinity arithmetic performed as per the
18ieee spec.'
19 WRITE( 6, FMT = * ) 'However, this is not an exhaustive test
20and does not'
21 WRITE( 6, FMT = * ) 'guarantee that infinity arithmetic meets
22the', ' ieee spec.'
23 END IF
24 WRITE( 6, FMT = * )
25 WRITE( 6, FMT = * ) 'We are about to check whether NaN arith‐
26metic'
27 WRITE( 6, FMT = * )'can be trusted. If this test hangs, set'
28 WRITE( 6, FMT = * ) 'ILAENV = 0 for ISPEC = 11 in LA‐
29PACK/SRC/ilaenv.f'
30 IEEEOK = ILAENV( 11, 'ILAENV', 'N', 1, 2, 3, 4 )
31 WRITE( 6, FMT = * )
32 IF( IEEEOK.EQ.0 ) THEN
33 WRITE( 6, FMT = * ) 'NaN arithmetic did not perform per the
34ieee spec'
35 ELSE
36 WRITE( 6, FMT = * )'NaN arithmetic performed as per the
37ieee', ' spec.'
38 WRITE( 6, FMT = * ) 'However, this is not an exhaustive test
39and does not'
40 WRITE( 6, FMT = * )'guarantee that NaN arithmetic meets the',
41' ieee spec.'
42 END IF
43 WRITE( 6, FMT = * )
44 END
45 INTEGER FUNCTION ILAENV( ISPEC, NAME, OPTS, N1, N2, N3, N4 )
46 CHARACTER*( * ) NAME, OPTS
47 INTEGER ISPEC, N1, N2, N3, N4 ILAENV is called from the LA‐
48PACK routines to choose problem‐dependent parameters for the lo‐
49cal environment. See ISPEC for a description of the parameters.
50This version provides a set of parameters which should give good,
52but not optimal, performance on many of the currently available
53computers. Users are encouraged to modify this subroutine to set
54the tuning parameters for their particular machine using the op‐
55tion and problem size information in the arguments.
56This routine will not function correctly if it is converted to
58all lower case. Converting it to all upper case is allowed.
59ISPEC (input) INTEGER Specifies the parameter to be returned as
61the value of ILAENV. = 1: the optimal blocksize; if this value
62is 1, an unblocked algorithm will give the best performance. =
632: the minimum block size for which the block routine should be
64used; if the usable block size is less than this value, an un‐
65blocked routine should be used. = 3: the crossover point (in a
66block routine, for N less than this value, an unblocked routine
67should be used) = 4: the number of shifts, used in the nonsymmet‐
68ric eigenvalue routines = 5: the minimum column dimension for
69blocking to be used; rectangular blocks must have dimension at
70least k by m, where k is given by ILAENV(2,...) and m by
71ILAENV(5,...) = 6: the crossover point for the SVD (when reduc‐
72ing an m by n matrix to bidiagonal form, if max(m,n)/min(m,n) ex‐
73ceeds this value, a QR factorization is used first to reduce the
74matrix to a triangular form.) = 7: the number of processors
75= 8: the crossover point for the multishift QR and QZ methods for
76nonsymmetric eigenvalue problems. = 9: maximum size of the sub‐
77problems at the bottom of the computation tree in the divide‐and‐
78conquer algorithm (used by xGELSD and xGESDD) =10: ieee NaN
79arithmetic can be trusted not to trap
80=11: infinity arithmetic can be trusted not to trap NAME (in‐
81put) CHARACTER*(*) The name of the calling subroutine, in either
82upper case or lower case. OPTS (input) CHARACTER*(*) The
83character options to the subroutine NAME, concatenated into a
84single character string. For example, UPLO = 'U', TRANS = 'T',
85and DIAG = 'N' for a triangular routine would be specified as
86OPTS = 'UTN'. N1 (input) INTEGER N2 (input) INTEGER N3
87(input) INTEGER N4 (input) INTEGER Problem dimensions for
88the subroutine NAME; these may not all be required.
89>= 0: the value of the parameter specified by ISPEC < 0: if
91ILAENV = ‐k, the k‐th argument had an illegal value. The follow‐
92ing conventions have been used when calling ILAENV from the LA‐
93PACK routines:
941) OPTS is a concatenation of all of the character options to
95 subroutine NAME, in the same order that they appear in the
96 argument list for NAME, even if they are not used in deter‐
97mining
98 the value of the parameter specified by ISPEC.
992) The problem dimensions N1, N2, N3, N4 are specified in the
100order
101 that they appear in the argument list for NAME. N1 is used
102 first, N2 second, and so on, and unused problem dimensions
103are
104 passed a value of ‐1.
1053) The parameter value returned by ILAENV is checked for validi‐
106ty in
107 the calling subroutine. For example, ILAENV is used to re‐
108trieve
109 the optimal blocksize for STRTRI as follows:
110 NB = ILAENV( 1, 'STRTRI', UPLO // DIAG, N, ‐1, ‐1, ‐1 )
112 IF( NB.LE.1 ) NB = MAX( 1, N )
113