LAPACK 3.12.0 LAPACK: Linear Algebra PACKage
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dlat2s.f
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1*> \brief \b DLAT2S converts a double-precision triangular matrix to a single-precision triangular matrix.
2*
3* =========== DOCUMENTATION ===========
4*
5* Online html documentation available at
6* http://www.netlib.org/lapack/explore-html/
7*
8*> \htmlonly
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14*> <a href="http://www.netlib.org/cgi-bin/netlibfiles.txt?format=txt&filename=/lapack/lapack_routine/dlat2s.f">
15*> [TXT]</a>
16*> \endhtmlonly
17*
18* Definition:
19* ===========
20*
21* SUBROUTINE DLAT2S( UPLO, N, A, LDA, SA, LDSA, INFO )
22*
23* .. Scalar Arguments ..
24* CHARACTER UPLO
25* INTEGER INFO, LDA, LDSA, N
26* ..
27* .. Array Arguments ..
28* REAL SA( LDSA, * )
29* DOUBLE PRECISION A( LDA, * )
30* ..
31*
32*
33*> \par Purpose:
34* =============
35*>
36*> \verbatim
37*>
38*> DLAT2S converts a DOUBLE PRECISION triangular matrix, SA, to a SINGLE
39*> PRECISION triangular matrix, A.
40*>
41*> RMAX is the overflow for the SINGLE PRECISION arithmetic
42*> DLAS2S checks that all the entries of A are between -RMAX and
43*> RMAX. If not the conversion is aborted and a flag is raised.
44*>
45*> This is an auxiliary routine so there is no argument checking.
46*> \endverbatim
47*
48* Arguments:
49* ==========
50*
51*> \param[in] UPLO
52*> \verbatim
53*> UPLO is CHARACTER*1
54*> = 'U': A is upper triangular;
55*> = 'L': A is lower triangular.
56*> \endverbatim
57*>
58*> \param[in] N
59*> \verbatim
60*> N is INTEGER
61*> The number of rows and columns of the matrix A. N >= 0.
62*> \endverbatim
63*>
64*> \param[in] A
65*> \verbatim
66*> A is DOUBLE PRECISION array, dimension (LDA,N)
67*> On entry, the N-by-N triangular coefficient matrix A.
68*> \endverbatim
69*>
70*> \param[in] LDA
71*> \verbatim
72*> LDA is INTEGER
73*> The leading dimension of the array A. LDA >= max(1,N).
74*> \endverbatim
75*>
76*> \param[out] SA
77*> \verbatim
78*> SA is REAL array, dimension (LDSA,N)
79*> Only the UPLO part of SA is referenced. On exit, if INFO=0,
80*> the N-by-N coefficient matrix SA; if INFO>0, the content of
81*> the UPLO part of SA is unspecified.
82*> \endverbatim
83*>
84*> \param[in] LDSA
85*> \verbatim
86*> LDSA is INTEGER
87*> The leading dimension of the array SA. LDSA >= max(1,M).
88*> \endverbatim
89*>
90*> \param[out] INFO
91*> \verbatim
92*> INFO is INTEGER
93*> = 0: successful exit.
94*> = 1: an entry of the matrix A is greater than the SINGLE
95*> PRECISION overflow threshold, in this case, the content
96*> of the UPLO part of SA in exit is unspecified.
97*> \endverbatim
98*
99* Authors:
100* ========
101*
102*> \author Univ. of Tennessee
103*> \author Univ. of California Berkeley
104*> \author Univ. of Colorado Denver
105*> \author NAG Ltd.
106*
107*> \ingroup _lat2_
108*
109* =====================================================================
110 SUBROUTINE dlat2s( UPLO, N, A, LDA, SA, LDSA, INFO )
111*
112* -- LAPACK auxiliary routine --
113* -- LAPACK is a software package provided by Univ. of Tennessee, --
114* -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
115*
116* .. Scalar Arguments ..
117 CHARACTER UPLO
118 INTEGER INFO, LDA, LDSA, N
119* ..
120* .. Array Arguments ..
121 REAL SA( LDSA, * )
122 DOUBLE PRECISION A( LDA, * )
123* ..
124*
125* =====================================================================
126*
127* .. Local Scalars ..
128 INTEGER I, J
129 DOUBLE PRECISION RMAX
130 LOGICAL UPPER
131* ..
132* .. External Functions ..
133 REAL SLAMCH
134 LOGICAL LSAME
135 EXTERNAL slamch, lsame
136* ..
137* .. Intrinsic Functions ..
138 INTRINSIC real
139* ..
140* .. Executable Statements ..
141*
142 rmax = slamch( 'O' )
143 upper = lsame( uplo, 'U' )
144 IF( upper ) THEN
145 DO 20 j = 1, n
146 DO 10 i = 1, j
147 IF( ( a( i, j ).LT.-rmax ) .OR. ( a( i, j ).GT.rmax ) )
148 \$ THEN
149 info = 1
150 GO TO 50
151 END IF
152 sa( i, j ) = real( a( i, j ) )
153 10 CONTINUE
154 20 CONTINUE
155 ELSE
156 DO 40 j = 1, n
157 DO 30 i = j, n
158 IF( ( a( i, j ).LT.-rmax ) .OR. ( a( i, j ).GT.rmax ) )
159 \$ THEN
160 info = 1
161 GO TO 50
162 END IF
163 sa( i, j ) = real( a( i, j ) )
164 30 CONTINUE
165 40 CONTINUE
166 END IF
167 50 CONTINUE
168*
169 RETURN
170*
171* End of DLAT2S
172*
173 END
subroutine dlat2s(uplo, n, a, lda, sa, ldsa, info)
DLAT2S converts a double-precision triangular matrix to a single-precision triangular matrix.
Definition dlat2s.f:111