LAPACK 3.12.0 LAPACK: Linear Algebra PACKage
Searching...
No Matches
slaswp.f
Go to the documentation of this file.
1*> \brief \b SLASWP performs a series of row interchanges on a general rectangular matrix.
2*
3* =========== DOCUMENTATION ===========
4*
5* Online html documentation available at
6* http://www.netlib.org/lapack/explore-html/
7*
8*> \htmlonly
10*> <a href="http://www.netlib.org/cgi-bin/netlibfiles.tgz?format=tgz&filename=/lapack/lapack_routine/slaswp.f">
11*> [TGZ]</a>
12*> <a href="http://www.netlib.org/cgi-bin/netlibfiles.zip?format=zip&filename=/lapack/lapack_routine/slaswp.f">
13*> [ZIP]</a>
14*> <a href="http://www.netlib.org/cgi-bin/netlibfiles.txt?format=txt&filename=/lapack/lapack_routine/slaswp.f">
15*> [TXT]</a>
16*> \endhtmlonly
17*
18* Definition:
19* ===========
20*
21* SUBROUTINE SLASWP( N, A, LDA, K1, K2, IPIV, INCX )
22*
23* .. Scalar Arguments ..
24* INTEGER INCX, K1, K2, LDA, N
25* ..
26* .. Array Arguments ..
27* INTEGER IPIV( * )
28* REAL A( LDA, * )
29* ..
30*
31*
32*> \par Purpose:
33* =============
34*>
35*> \verbatim
36*>
37*> SLASWP performs a series of row interchanges on the matrix A.
38*> One row interchange is initiated for each of rows K1 through K2 of A.
39*> \endverbatim
40*
41* Arguments:
42* ==========
43*
44*> \param[in] N
45*> \verbatim
46*> N is INTEGER
47*> The number of columns of the matrix A.
48*> \endverbatim
49*>
50*> \param[in,out] A
51*> \verbatim
52*> A is REAL array, dimension (LDA,N)
53*> On entry, the matrix of column dimension N to which the row
54*> interchanges will be applied.
55*> On exit, the permuted matrix.
56*> \endverbatim
57*>
58*> \param[in] LDA
59*> \verbatim
60*> LDA is INTEGER
61*> The leading dimension of the array A.
62*> \endverbatim
63*>
64*> \param[in] K1
65*> \verbatim
66*> K1 is INTEGER
67*> The first element of IPIV for which a row interchange will
68*> be done.
69*> \endverbatim
70*>
71*> \param[in] K2
72*> \verbatim
73*> K2 is INTEGER
74*> (K2-K1+1) is the number of elements of IPIV for which a row
75*> interchange will be done.
76*> \endverbatim
77*>
78*> \param[in] IPIV
79*> \verbatim
80*> IPIV is INTEGER array, dimension (K1+(K2-K1)*abs(INCX))
81*> The vector of pivot indices. Only the elements in positions
82*> K1 through K1+(K2-K1)*abs(INCX) of IPIV are accessed.
83*> IPIV(K1+(K-K1)*abs(INCX)) = L implies rows K and L are to be
84*> interchanged.
85*> \endverbatim
86*>
87*> \param[in] INCX
88*> \verbatim
89*> INCX is INTEGER
90*> The increment between successive values of IPIV. If INCX
91*> is negative, the pivots are applied in reverse order.
92*> \endverbatim
93*
94* Authors:
95* ========
96*
97*> \author Univ. of Tennessee
98*> \author Univ. of California Berkeley
99*> \author Univ. of Colorado Denver
100*> \author NAG Ltd.
101*
102*> \ingroup laswp
103*
104*> \par Further Details:
105* =====================
106*>
107*> \verbatim
108*>
109*> Modified by
110*> R. C. Whaley, Computer Science Dept., Univ. of Tenn., Knoxville, USA
111*> \endverbatim
112*>
113* =====================================================================
114 SUBROUTINE slaswp( N, A, LDA, K1, K2, IPIV, INCX )
115*
116* -- LAPACK auxiliary routine --
117* -- LAPACK is a software package provided by Univ. of Tennessee, --
118* -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
119*
120* .. Scalar Arguments ..
121 INTEGER INCX, K1, K2, LDA, N
122* ..
123* .. Array Arguments ..
124 INTEGER IPIV( * )
125 REAL A( LDA, * )
126* ..
127*
128* =====================================================================
129*
130* .. Local Scalars ..
131 INTEGER I, I1, I2, INC, IP, IX, IX0, J, K, N32
132 REAL TEMP
133* ..
134* .. Executable Statements ..
135*
136* Interchange row I with row IPIV(K1+(I-K1)*abs(INCX)) for each of rows
137* K1 through K2.
138*
139 IF( incx.GT.0 ) THEN
140 ix0 = k1
141 i1 = k1
142 i2 = k2
143 inc = 1
144 ELSE IF( incx.LT.0 ) THEN
145 ix0 = k1 + ( k1-k2 )*incx
146 i1 = k2
147 i2 = k1
148 inc = -1
149 ELSE
150 RETURN
151 END IF
152*
153 n32 = ( n / 32 )*32
154 IF( n32.NE.0 ) THEN
155 DO 30 j = 1, n32, 32
156 ix = ix0
157 DO 20 i = i1, i2, inc
158 ip = ipiv( ix )
159 IF( ip.NE.i ) THEN
160 DO 10 k = j, j + 31
161 temp = a( i, k )
162 a( i, k ) = a( ip, k )
163 a( ip, k ) = temp
164 10 CONTINUE
165 END IF
166 ix = ix + incx
167 20 CONTINUE
168 30 CONTINUE
169 END IF
170 IF( n32.NE.n ) THEN
171 n32 = n32 + 1
172 ix = ix0
173 DO 50 i = i1, i2, inc
174 ip = ipiv( ix )
175 IF( ip.NE.i ) THEN
176 DO 40 k = n32, n
177 temp = a( i, k )
178 a( i, k ) = a( ip, k )
179 a( ip, k ) = temp
180 40 CONTINUE
181 END IF
182 ix = ix + incx
183 50 CONTINUE
184 END IF
185*
186 RETURN
187*
188* End of SLASWP
189*
190 END
subroutine slaswp(n, a, lda, k1, k2, ipiv, incx)
SLASWP performs a series of row interchanges on a general rectangular matrix.
Definition slaswp.f:115