LAPACK  3.10.0 LAPACK: Linear Algebra PACKage
zlavsy.f
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1 *> \brief \b ZLAVSY
2 *
3 * =========== DOCUMENTATION ===========
4 *
5 * Online html documentation available at
6 * http://www.netlib.org/lapack/explore-html/
7 *
8 * Definition:
9 * ===========
10 *
11 * SUBROUTINE ZLAVSY( UPLO, TRANS, DIAG, N, NRHS, A, LDA, IPIV, B,
12 * LDB, INFO )
13 *
14 * .. Scalar Arguments ..
15 * CHARACTER DIAG, TRANS, UPLO
16 * INTEGER INFO, LDA, LDB, N, NRHS
17 * ..
18 * .. Array Arguments ..
19 * INTEGER IPIV( * )
20 * COMPLEX*16 A( LDA, * ), B( LDB, * )
21 * ..
22 *
23 *
24 *> \par Purpose:
25 * =============
26 *>
27 *> \verbatim
28 *>
29 *> ZLAVSY performs one of the matrix-vector operations
30 *> x := A*x or x := A'*x,
31 *> where x is an N element vector and A is one of the factors
32 *> from the block U*D*U' or L*D*L' factorization computed by ZSYTRF.
33 *>
34 *> If TRANS = 'N', multiplies by U or U * D (or L or L * D)
35 *> If TRANS = 'T', multiplies by U' or D * U' (or L' or D * L')
36 *> \endverbatim
37 *
38 * Arguments:
39 * ==========
40 *
41 *> \param[in] UPLO
42 *> \verbatim
43 *> UPLO is CHARACTER*1
44 *> Specifies whether the factor stored in A is upper or lower
45 *> triangular.
46 *> = 'U': Upper triangular
47 *> = 'L': Lower triangular
48 *> \endverbatim
49 *>
50 *> \param[in] TRANS
51 *> \verbatim
52 *> TRANS is CHARACTER*1
53 *> Specifies the operation to be performed:
54 *> = 'N': x := A*x
55 *> = 'T': x := A'*x
56 *> \endverbatim
57 *>
58 *> \param[in] DIAG
59 *> \verbatim
60 *> DIAG is CHARACTER*1
61 *> Specifies whether or not the diagonal blocks are unit
62 *> matrices. If the diagonal blocks are assumed to be unit,
63 *> then A = U or A = L, otherwise A = U*D or A = L*D.
64 *> = 'U': Diagonal blocks are assumed to be unit matrices.
65 *> = 'N': Diagonal blocks are assumed to be non-unit matrices.
66 *> \endverbatim
67 *>
68 *> \param[in] N
69 *> \verbatim
70 *> N is INTEGER
71 *> The number of rows and columns of the matrix A. N >= 0.
72 *> \endverbatim
73 *>
74 *> \param[in] NRHS
75 *> \verbatim
76 *> NRHS is INTEGER
77 *> The number of right hand sides, i.e., the number of vectors
78 *> x to be multiplied by A. NRHS >= 0.
79 *> \endverbatim
80 *>
81 *> \param[in] A
82 *> \verbatim
83 *> A is COMPLEX*16 array, dimension (LDA,N)
84 *> The block diagonal matrix D and the multipliers used to
85 *> obtain the factor U or L as computed by ZSYTRF.
86 *> Stored as a 2-D triangular matrix.
87 *> \endverbatim
88 *>
89 *> \param[in] LDA
90 *> \verbatim
91 *> LDA is INTEGER
92 *> The leading dimension of the array A. LDA >= max(1,N).
93 *> \endverbatim
94 *>
95 *> \param[in] IPIV
96 *> \verbatim
97 *> IPIV is INTEGER array, dimension (N)
98 *> Details of the interchanges and the block structure of D,
99 *> as determined by ZSYTRF.
100 *>
101 *> If UPLO = 'U':
102 *> If IPIV(k) > 0, then rows and columns k and IPIV(k)
103 *> were interchanged and D(k,k) is a 1-by-1 diagonal block.
104 *> (If IPIV( k ) = k, no interchange was done).
105 *>
106 *> If IPIV(k) = IPIV(k-1) < 0, then rows and
107 *> columns k-1 and -IPIV(k) were interchanged,
108 *> D(k-1:k,k-1:k) is a 2-by-2 diagonal block.
109 *>
110 *> If UPLO = 'L':
111 *> If IPIV(k) > 0, then rows and columns k and IPIV(k)
112 *> were interchanged and D(k,k) is a 1-by-1 diagonal block.
113 *> (If IPIV( k ) = k, no interchange was done).
114 *>
115 *> If IPIV(k) = IPIV(k+1) < 0, then rows and
116 *> columns k+1 and -IPIV(k) were interchanged,
117 *> D(k:k+1,k:k+1) is a 2-by-2 diagonal block.
118 *> \endverbatim
119 *>
120 *> \param[in,out] B
121 *> \verbatim
122 *> B is COMPLEX*16 array, dimension (LDB,NRHS)
123 *> On entry, B contains NRHS vectors of length N.
124 *> On exit, B is overwritten with the product A * B.
125 *> \endverbatim
126 *>
127 *> \param[in] LDB
128 *> \verbatim
129 *> LDB is INTEGER
130 *> The leading dimension of the array B. LDB >= max(1,N).
131 *> \endverbatim
132 *>
133 *> \param[out] INFO
134 *> \verbatim
135 *> INFO is INTEGER
136 *> = 0: successful exit
137 *> < 0: if INFO = -k, the k-th argument had an illegal value
138 *> \endverbatim
139 *
140 * Authors:
141 * ========
142 *
143 *> \author Univ. of Tennessee
144 *> \author Univ. of California Berkeley
145 *> \author Univ. of Colorado Denver
146 *> \author NAG Ltd.
147 *
148 *> \ingroup complex16_lin
149 *
150 * =====================================================================
151  SUBROUTINE zlavsy( UPLO, TRANS, DIAG, N, NRHS, A, LDA, IPIV, B,
152  \$ LDB, INFO )
153 *
154 * -- LAPACK test routine --
155 * -- LAPACK is a software package provided by Univ. of Tennessee, --
156 * -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
157 *
158 * .. Scalar Arguments ..
159  CHARACTER DIAG, TRANS, UPLO
160  INTEGER INFO, LDA, LDB, N, NRHS
161 * ..
162 * .. Array Arguments ..
163  INTEGER IPIV( * )
164  COMPLEX*16 A( LDA, * ), B( LDB, * )
165 * ..
166 *
167 * =====================================================================
168 *
169 * .. Parameters ..
170  COMPLEX*16 CONE
171  parameter( cone = ( 1.0d+0, 0.0d+0 ) )
172 * ..
173 * .. Local Scalars ..
174  LOGICAL NOUNIT
175  INTEGER J, K, KP
176  COMPLEX*16 D11, D12, D21, D22, T1, T2
177 * ..
178 * .. External Functions ..
179  LOGICAL LSAME
180  EXTERNAL lsame
181 * ..
182 * .. External Subroutines ..
183  EXTERNAL xerbla, zgemv, zgeru, zscal, zswap
184 * ..
185 * .. Intrinsic Functions ..
186  INTRINSIC abs, max
187 * ..
188 * .. Executable Statements ..
189 *
190 * Test the input parameters.
191 *
192  info = 0
193  IF( .NOT.lsame( uplo, 'U' ) .AND. .NOT.lsame( uplo, 'L' ) ) THEN
194  info = -1
195  ELSE IF( .NOT.lsame( trans, 'N' ) .AND. .NOT.lsame( trans, 'T' ) )
196  \$ THEN
197  info = -2
198  ELSE IF( .NOT.lsame( diag, 'U' ) .AND. .NOT.lsame( diag, 'N' ) )
199  \$ THEN
200  info = -3
201  ELSE IF( n.LT.0 ) THEN
202  info = -4
203  ELSE IF( lda.LT.max( 1, n ) ) THEN
204  info = -6
205  ELSE IF( ldb.LT.max( 1, n ) ) THEN
206  info = -9
207  END IF
208  IF( info.NE.0 ) THEN
209  CALL xerbla( 'ZLAVSY ', -info )
210  RETURN
211  END IF
212 *
213 * Quick return if possible.
214 *
215  IF( n.EQ.0 )
216  \$ RETURN
217 *
218  nounit = lsame( diag, 'N' )
219 *------------------------------------------
220 *
221 * Compute B := A * B (No transpose)
222 *
223 *------------------------------------------
224  IF( lsame( trans, 'N' ) ) THEN
225 *
226 * Compute B := U*B
227 * where U = P(m)*inv(U(m))* ... *P(1)*inv(U(1))
228 *
229  IF( lsame( uplo, 'U' ) ) THEN
230 *
231 * Loop forward applying the transformations.
232 *
233  k = 1
234  10 CONTINUE
235  IF( k.GT.n )
236  \$ GO TO 30
237  IF( ipiv( k ).GT.0 ) THEN
238 *
239 * 1 x 1 pivot block
240 *
241 * Multiply by the diagonal element if forming U * D.
242 *
243  IF( nounit )
244  \$ CALL zscal( nrhs, a( k, k ), b( k, 1 ), ldb )
245 *
246 * Multiply by P(K) * inv(U(K)) if K > 1.
247 *
248  IF( k.GT.1 ) THEN
249 *
250 * Apply the transformation.
251 *
252  CALL zgeru( k-1, nrhs, cone, a( 1, k ), 1, b( k, 1 ),
253  \$ ldb, b( 1, 1 ), ldb )
254 *
255 * Interchange if P(K) != I.
256 *
257  kp = ipiv( k )
258  IF( kp.NE.k )
259  \$ CALL zswap( nrhs, b( k, 1 ), ldb, b( kp, 1 ), ldb )
260  END IF
261  k = k + 1
262  ELSE
263 *
264 * 2 x 2 pivot block
265 *
266 * Multiply by the diagonal block if forming U * D.
267 *
268  IF( nounit ) THEN
269  d11 = a( k, k )
270  d22 = a( k+1, k+1 )
271  d12 = a( k, k+1 )
272  d21 = d12
273  DO 20 j = 1, nrhs
274  t1 = b( k, j )
275  t2 = b( k+1, j )
276  b( k, j ) = d11*t1 + d12*t2
277  b( k+1, j ) = d21*t1 + d22*t2
278  20 CONTINUE
279  END IF
280 *
281 * Multiply by P(K) * inv(U(K)) if K > 1.
282 *
283  IF( k.GT.1 ) THEN
284 *
285 * Apply the transformations.
286 *
287  CALL zgeru( k-1, nrhs, cone, a( 1, k ), 1, b( k, 1 ),
288  \$ ldb, b( 1, 1 ), ldb )
289  CALL zgeru( k-1, nrhs, cone, a( 1, k+1 ), 1,
290  \$ b( k+1, 1 ), ldb, b( 1, 1 ), ldb )
291 *
292 * Interchange if P(K) != I.
293 *
294  kp = abs( ipiv( k ) )
295  IF( kp.NE.k )
296  \$ CALL zswap( nrhs, b( k, 1 ), ldb, b( kp, 1 ), ldb )
297  END IF
298  k = k + 2
299  END IF
300  GO TO 10
301  30 CONTINUE
302 *
303 * Compute B := L*B
304 * where L = P(1)*inv(L(1))* ... *P(m)*inv(L(m)) .
305 *
306  ELSE
307 *
308 * Loop backward applying the transformations to B.
309 *
310  k = n
311  40 CONTINUE
312  IF( k.LT.1 )
313  \$ GO TO 60
314 *
315 * Test the pivot index. If greater than zero, a 1 x 1
316 * pivot was used, otherwise a 2 x 2 pivot was used.
317 *
318  IF( ipiv( k ).GT.0 ) THEN
319 *
320 * 1 x 1 pivot block:
321 *
322 * Multiply by the diagonal element if forming L * D.
323 *
324  IF( nounit )
325  \$ CALL zscal( nrhs, a( k, k ), b( k, 1 ), ldb )
326 *
327 * Multiply by P(K) * inv(L(K)) if K < N.
328 *
329  IF( k.NE.n ) THEN
330  kp = ipiv( k )
331 *
332 * Apply the transformation.
333 *
334  CALL zgeru( n-k, nrhs, cone, a( k+1, k ), 1,
335  \$ b( k, 1 ), ldb, b( k+1, 1 ), ldb )
336 *
337 * Interchange if a permutation was applied at the
338 * K-th step of the factorization.
339 *
340  IF( kp.NE.k )
341  \$ CALL zswap( nrhs, b( k, 1 ), ldb, b( kp, 1 ), ldb )
342  END IF
343  k = k - 1
344 *
345  ELSE
346 *
347 * 2 x 2 pivot block:
348 *
349 * Multiply by the diagonal block if forming L * D.
350 *
351  IF( nounit ) THEN
352  d11 = a( k-1, k-1 )
353  d22 = a( k, k )
354  d21 = a( k, k-1 )
355  d12 = d21
356  DO 50 j = 1, nrhs
357  t1 = b( k-1, j )
358  t2 = b( k, j )
359  b( k-1, j ) = d11*t1 + d12*t2
360  b( k, j ) = d21*t1 + d22*t2
361  50 CONTINUE
362  END IF
363 *
364 * Multiply by P(K) * inv(L(K)) if K < N.
365 *
366  IF( k.NE.n ) THEN
367 *
368 * Apply the transformation.
369 *
370  CALL zgeru( n-k, nrhs, cone, a( k+1, k ), 1,
371  \$ b( k, 1 ), ldb, b( k+1, 1 ), ldb )
372  CALL zgeru( n-k, nrhs, cone, a( k+1, k-1 ), 1,
373  \$ b( k-1, 1 ), ldb, b( k+1, 1 ), ldb )
374 *
375 * Interchange if a permutation was applied at the
376 * K-th step of the factorization.
377 *
378  kp = abs( ipiv( k ) )
379  IF( kp.NE.k )
380  \$ CALL zswap( nrhs, b( k, 1 ), ldb, b( kp, 1 ), ldb )
381  END IF
382  k = k - 2
383  END IF
384  GO TO 40
385  60 CONTINUE
386  END IF
387 *----------------------------------------
388 *
389 * Compute B := A' * B (transpose)
390 *
391 *----------------------------------------
392  ELSE IF( lsame( trans, 'T' ) ) THEN
393 *
394 * Form B := U'*B
395 * where U = P(m)*inv(U(m))* ... *P(1)*inv(U(1))
396 * and U' = inv(U'(1))*P(1)* ... *inv(U'(m))*P(m)
397 *
398  IF( lsame( uplo, 'U' ) ) THEN
399 *
400 * Loop backward applying the transformations.
401 *
402  k = n
403  70 CONTINUE
404  IF( k.LT.1 )
405  \$ GO TO 90
406 *
407 * 1 x 1 pivot block.
408 *
409  IF( ipiv( k ).GT.0 ) THEN
410  IF( k.GT.1 ) THEN
411 *
412 * Interchange if P(K) != I.
413 *
414  kp = ipiv( k )
415  IF( kp.NE.k )
416  \$ CALL zswap( nrhs, b( k, 1 ), ldb, b( kp, 1 ), ldb )
417 *
418 * Apply the transformation
419 *
420  CALL zgemv( 'Transpose', k-1, nrhs, cone, b, ldb,
421  \$ a( 1, k ), 1, cone, b( k, 1 ), ldb )
422  END IF
423  IF( nounit )
424  \$ CALL zscal( nrhs, a( k, k ), b( k, 1 ), ldb )
425  k = k - 1
426 *
427 * 2 x 2 pivot block.
428 *
429  ELSE
430  IF( k.GT.2 ) THEN
431 *
432 * Interchange if P(K) != I.
433 *
434  kp = abs( ipiv( k ) )
435  IF( kp.NE.k-1 )
436  \$ CALL zswap( nrhs, b( k-1, 1 ), ldb, b( kp, 1 ),
437  \$ ldb )
438 *
439 * Apply the transformations
440 *
441  CALL zgemv( 'Transpose', k-2, nrhs, cone, b, ldb,
442  \$ a( 1, k ), 1, cone, b( k, 1 ), ldb )
443  CALL zgemv( 'Transpose', k-2, nrhs, cone, b, ldb,
444  \$ a( 1, k-1 ), 1, cone, b( k-1, 1 ), ldb )
445  END IF
446 *
447 * Multiply by the diagonal block if non-unit.
448 *
449  IF( nounit ) THEN
450  d11 = a( k-1, k-1 )
451  d22 = a( k, k )
452  d12 = a( k-1, k )
453  d21 = d12
454  DO 80 j = 1, nrhs
455  t1 = b( k-1, j )
456  t2 = b( k, j )
457  b( k-1, j ) = d11*t1 + d12*t2
458  b( k, j ) = d21*t1 + d22*t2
459  80 CONTINUE
460  END IF
461  k = k - 2
462  END IF
463  GO TO 70
464  90 CONTINUE
465 *
466 * Form B := L'*B
467 * where L = P(1)*inv(L(1))* ... *P(m)*inv(L(m))
468 * and L' = inv(L'(m))*P(m)* ... *inv(L'(1))*P(1)
469 *
470  ELSE
471 *
472 * Loop forward applying the L-transformations.
473 *
474  k = 1
475  100 CONTINUE
476  IF( k.GT.n )
477  \$ GO TO 120
478 *
479 * 1 x 1 pivot block
480 *
481  IF( ipiv( k ).GT.0 ) THEN
482  IF( k.LT.n ) THEN
483 *
484 * Interchange if P(K) != I.
485 *
486  kp = ipiv( k )
487  IF( kp.NE.k )
488  \$ CALL zswap( nrhs, b( k, 1 ), ldb, b( kp, 1 ), ldb )
489 *
490 * Apply the transformation
491 *
492  CALL zgemv( 'Transpose', n-k, nrhs, cone, b( k+1, 1 ),
493  \$ ldb, a( k+1, k ), 1, cone, b( k, 1 ), ldb )
494  END IF
495  IF( nounit )
496  \$ CALL zscal( nrhs, a( k, k ), b( k, 1 ), ldb )
497  k = k + 1
498 *
499 * 2 x 2 pivot block.
500 *
501  ELSE
502  IF( k.LT.n-1 ) THEN
503 *
504 * Interchange if P(K) != I.
505 *
506  kp = abs( ipiv( k ) )
507  IF( kp.NE.k+1 )
508  \$ CALL zswap( nrhs, b( k+1, 1 ), ldb, b( kp, 1 ),
509  \$ ldb )
510 *
511 * Apply the transformation
512 *
513  CALL zgemv( 'Transpose', n-k-1, nrhs, cone,
514  \$ b( k+2, 1 ), ldb, a( k+2, k+1 ), 1, cone,
515  \$ b( k+1, 1 ), ldb )
516  CALL zgemv( 'Transpose', n-k-1, nrhs, cone,
517  \$ b( k+2, 1 ), ldb, a( k+2, k ), 1, cone,
518  \$ b( k, 1 ), ldb )
519  END IF
520 *
521 * Multiply by the diagonal block if non-unit.
522 *
523  IF( nounit ) THEN
524  d11 = a( k, k )
525  d22 = a( k+1, k+1 )
526  d21 = a( k+1, k )
527  d12 = d21
528  DO 110 j = 1, nrhs
529  t1 = b( k, j )
530  t2 = b( k+1, j )
531  b( k, j ) = d11*t1 + d12*t2
532  b( k+1, j ) = d21*t1 + d22*t2
533  110 CONTINUE
534  END IF
535  k = k + 2
536  END IF
537  GO TO 100
538  120 CONTINUE
539  END IF
540  END IF
541  RETURN
542 *
543 * End of ZLAVSY
544 *
545  END
subroutine xerbla(SRNAME, INFO)
XERBLA
Definition: xerbla.f:60
subroutine zswap(N, ZX, INCX, ZY, INCY)
ZSWAP
Definition: zswap.f:81
subroutine zscal(N, ZA, ZX, INCX)
ZSCAL
Definition: zscal.f:78
subroutine zgeru(M, N, ALPHA, X, INCX, Y, INCY, A, LDA)
ZGERU
Definition: zgeru.f:130
subroutine zgemv(TRANS, M, N, ALPHA, A, LDA, X, INCX, BETA, Y, INCY)
ZGEMV
Definition: zgemv.f:158
subroutine zlavsy(UPLO, TRANS, DIAG, N, NRHS, A, LDA, IPIV, B, LDB, INFO)
ZLAVSY
Definition: zlavsy.f:153