 LAPACK  3.8.0 LAPACK: Linear Algebra PACKage

## ◆ zlavsy()

 subroutine zlavsy ( character UPLO, character TRANS, character DIAG, integer N, integer NRHS, complex*16, dimension( lda, * ) A, integer LDA, integer, dimension( * ) IPIV, complex*16, dimension( ldb, * ) B, integer LDB, integer INFO )

ZLAVSY

Purpose:
``` ZLAVSY performs one of the matrix-vector operations
x := A*x  or  x := A'*x,
where x is an N element vector and  A is one of the factors
from the block U*D*U' or L*D*L' factorization computed by ZSYTRF.

If TRANS = 'N', multiplies by U  or U * D  (or L  or L * D)
If TRANS = 'T', multiplies by U' or D * U' (or L' or D * L')```
Parameters
 [in] UPLO ``` UPLO is CHARACTER*1 Specifies whether the factor stored in A is upper or lower triangular. = 'U': Upper triangular = 'L': Lower triangular``` [in] TRANS ``` TRANS is CHARACTER*1 Specifies the operation to be performed: = 'N': x := A*x = 'T': x := A'*x``` [in] DIAG ``` DIAG is CHARACTER*1 Specifies whether or not the diagonal blocks are unit matrices. If the diagonal blocks are assumed to be unit, then A = U or A = L, otherwise A = U*D or A = L*D. = 'U': Diagonal blocks are assumed to be unit matrices. = 'N': Diagonal blocks are assumed to be non-unit matrices.``` [in] N ``` N is INTEGER The number of rows and columns of the matrix A. N >= 0.``` [in] NRHS ``` NRHS is INTEGER The number of right hand sides, i.e., the number of vectors x to be multiplied by A. NRHS >= 0.``` [in] A ``` A is COMPLEX*16 array, dimension (LDA,N) The block diagonal matrix D and the multipliers used to obtain the factor U or L as computed by ZSYTRF. Stored as a 2-D triangular matrix.``` [in] LDA ``` LDA is INTEGER The leading dimension of the array A. LDA >= max(1,N).``` [in] IPIV ``` IPIV is INTEGER array, dimension (N) Details of the interchanges and the block structure of D, as determined by ZSYTRF. If UPLO = 'U': If IPIV(k) > 0, then rows and columns k and IPIV(k) were interchanged and D(k,k) is a 1-by-1 diagonal block. (If IPIV( k ) = k, no interchange was done). If IPIV(k) = IPIV(k-1) < 0, then rows and columns k-1 and -IPIV(k) were interchanged, D(k-1:k,k-1:k) is a 2-by-2 diagonal block. If UPLO = 'L': If IPIV(k) > 0, then rows and columns k and IPIV(k) were interchanged and D(k,k) is a 1-by-1 diagonal block. (If IPIV( k ) = k, no interchange was done). If IPIV(k) = IPIV(k+1) < 0, then rows and columns k+1 and -IPIV(k) were interchanged, D(k:k+1,k:k+1) is a 2-by-2 diagonal block.``` [in,out] B ``` B is COMPLEX*16 array, dimension (LDB,NRHS) On entry, B contains NRHS vectors of length N. On exit, B is overwritten with the product A * B.``` [in] LDB ``` LDB is INTEGER The leading dimension of the array B. LDB >= max(1,N).``` [out] INFO ``` INFO is INTEGER = 0: successful exit < 0: if INFO = -k, the k-th argument had an illegal value```
Date
November 2013

Definition at line 155 of file zlavsy.f.

155 *
156 * -- LAPACK test routine (version 3.5.0) --
157 * -- LAPACK is a software package provided by Univ. of Tennessee, --
158 * -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
159 * November 2013
160 *
161 * .. Scalar Arguments ..
162  CHARACTER diag, trans, uplo
163  INTEGER info, lda, ldb, n, nrhs
164 * ..
165 * .. Array Arguments ..
166  INTEGER ipiv( * )
167  COMPLEX*16 a( lda, * ), b( ldb, * )
168 * ..
169 *
170 * =====================================================================
171 *
172 * .. Parameters ..
173  COMPLEX*16 cone
174  parameter( cone = ( 1.0d+0, 0.0d+0 ) )
175 * ..
176 * .. Local Scalars ..
177  LOGICAL nounit
178  INTEGER j, k, kp
179  COMPLEX*16 d11, d12, d21, d22, t1, t2
180 * ..
181 * .. External Functions ..
182  LOGICAL lsame
183  EXTERNAL lsame
184 * ..
185 * .. External Subroutines ..
186  EXTERNAL xerbla, zgemv, zgeru, zscal, zswap
187 * ..
188 * .. Intrinsic Functions ..
189  INTRINSIC abs, max
190 * ..
191 * .. Executable Statements ..
192 *
193 * Test the input parameters.
194 *
195  info = 0
196  IF( .NOT.lsame( uplo, 'U' ) .AND. .NOT.lsame( uplo, 'L' ) ) THEN
197  info = -1
198  ELSE IF( .NOT.lsame( trans, 'N' ) .AND. .NOT.lsame( trans, 'T' ) )
199  \$ THEN
200  info = -2
201  ELSE IF( .NOT.lsame( diag, 'U' ) .AND. .NOT.lsame( diag, 'N' ) )
202  \$ THEN
203  info = -3
204  ELSE IF( n.LT.0 ) THEN
205  info = -4
206  ELSE IF( lda.LT.max( 1, n ) ) THEN
207  info = -6
208  ELSE IF( ldb.LT.max( 1, n ) ) THEN
209  info = -9
210  END IF
211  IF( info.NE.0 ) THEN
212  CALL xerbla( 'ZLAVSY ', -info )
213  RETURN
214  END IF
215 *
216 * Quick return if possible.
217 *
218  IF( n.EQ.0 )
219  \$ RETURN
220 *
221  nounit = lsame( diag, 'N' )
222 *------------------------------------------
223 *
224 * Compute B := A * B (No transpose)
225 *
226 *------------------------------------------
227  IF( lsame( trans, 'N' ) ) THEN
228 *
229 * Compute B := U*B
230 * where U = P(m)*inv(U(m))* ... *P(1)*inv(U(1))
231 *
232  IF( lsame( uplo, 'U' ) ) THEN
233 *
234 * Loop forward applying the transformations.
235 *
236  k = 1
237  10 CONTINUE
238  IF( k.GT.n )
239  \$ GO TO 30
240  IF( ipiv( k ).GT.0 ) THEN
241 *
242 * 1 x 1 pivot block
243 *
244 * Multiply by the diagonal element if forming U * D.
245 *
246  IF( nounit )
247  \$ CALL zscal( nrhs, a( k, k ), b( k, 1 ), ldb )
248 *
249 * Multiply by P(K) * inv(U(K)) if K > 1.
250 *
251  IF( k.GT.1 ) THEN
252 *
253 * Apply the transformation.
254 *
255  CALL zgeru( k-1, nrhs, cone, a( 1, k ), 1, b( k, 1 ),
256  \$ ldb, b( 1, 1 ), ldb )
257 *
258 * Interchange if P(K) != I.
259 *
260  kp = ipiv( k )
261  IF( kp.NE.k )
262  \$ CALL zswap( nrhs, b( k, 1 ), ldb, b( kp, 1 ), ldb )
263  END IF
264  k = k + 1
265  ELSE
266 *
267 * 2 x 2 pivot block
268 *
269 * Multiply by the diagonal block if forming U * D.
270 *
271  IF( nounit ) THEN
272  d11 = a( k, k )
273  d22 = a( k+1, k+1 )
274  d12 = a( k, k+1 )
275  d21 = d12
276  DO 20 j = 1, nrhs
277  t1 = b( k, j )
278  t2 = b( k+1, j )
279  b( k, j ) = d11*t1 + d12*t2
280  b( k+1, j ) = d21*t1 + d22*t2
281  20 CONTINUE
282  END IF
283 *
284 * Multiply by P(K) * inv(U(K)) if K > 1.
285 *
286  IF( k.GT.1 ) THEN
287 *
288 * Apply the transformations.
289 *
290  CALL zgeru( k-1, nrhs, cone, a( 1, k ), 1, b( k, 1 ),
291  \$ ldb, b( 1, 1 ), ldb )
292  CALL zgeru( k-1, nrhs, cone, a( 1, k+1 ), 1,
293  \$ b( k+1, 1 ), ldb, b( 1, 1 ), ldb )
294 *
295 * Interchange if P(K) != I.
296 *
297  kp = abs( ipiv( k ) )
298  IF( kp.NE.k )
299  \$ CALL zswap( nrhs, b( k, 1 ), ldb, b( kp, 1 ), ldb )
300  END IF
301  k = k + 2
302  END IF
303  GO TO 10
304  30 CONTINUE
305 *
306 * Compute B := L*B
307 * where L = P(1)*inv(L(1))* ... *P(m)*inv(L(m)) .
308 *
309  ELSE
310 *
311 * Loop backward applying the transformations to B.
312 *
313  k = n
314  40 CONTINUE
315  IF( k.LT.1 )
316  \$ GO TO 60
317 *
318 * Test the pivot index. If greater than zero, a 1 x 1
319 * pivot was used, otherwise a 2 x 2 pivot was used.
320 *
321  IF( ipiv( k ).GT.0 ) THEN
322 *
323 * 1 x 1 pivot block:
324 *
325 * Multiply by the diagonal element if forming L * D.
326 *
327  IF( nounit )
328  \$ CALL zscal( nrhs, a( k, k ), b( k, 1 ), ldb )
329 *
330 * Multiply by P(K) * inv(L(K)) if K < N.
331 *
332  IF( k.NE.n ) THEN
333  kp = ipiv( k )
334 *
335 * Apply the transformation.
336 *
337  CALL zgeru( n-k, nrhs, cone, a( k+1, k ), 1,
338  \$ b( k, 1 ), ldb, b( k+1, 1 ), ldb )
339 *
340 * Interchange if a permutation was applied at the
341 * K-th step of the factorization.
342 *
343  IF( kp.NE.k )
344  \$ CALL zswap( nrhs, b( k, 1 ), ldb, b( kp, 1 ), ldb )
345  END IF
346  k = k - 1
347 *
348  ELSE
349 *
350 * 2 x 2 pivot block:
351 *
352 * Multiply by the diagonal block if forming L * D.
353 *
354  IF( nounit ) THEN
355  d11 = a( k-1, k-1 )
356  d22 = a( k, k )
357  d21 = a( k, k-1 )
358  d12 = d21
359  DO 50 j = 1, nrhs
360  t1 = b( k-1, j )
361  t2 = b( k, j )
362  b( k-1, j ) = d11*t1 + d12*t2
363  b( k, j ) = d21*t1 + d22*t2
364  50 CONTINUE
365  END IF
366 *
367 * Multiply by P(K) * inv(L(K)) if K < N.
368 *
369  IF( k.NE.n ) THEN
370 *
371 * Apply the transformation.
372 *
373  CALL zgeru( n-k, nrhs, cone, a( k+1, k ), 1,
374  \$ b( k, 1 ), ldb, b( k+1, 1 ), ldb )
375  CALL zgeru( n-k, nrhs, cone, a( k+1, k-1 ), 1,
376  \$ b( k-1, 1 ), ldb, b( k+1, 1 ), ldb )
377 *
378 * Interchange if a permutation was applied at the
379 * K-th step of the factorization.
380 *
381  kp = abs( ipiv( k ) )
382  IF( kp.NE.k )
383  \$ CALL zswap( nrhs, b( k, 1 ), ldb, b( kp, 1 ), ldb )
384  END IF
385  k = k - 2
386  END IF
387  GO TO 40
388  60 CONTINUE
389  END IF
390 *----------------------------------------
391 *
392 * Compute B := A' * B (transpose)
393 *
394 *----------------------------------------
395  ELSE IF( lsame( trans, 'T' ) ) THEN
396 *
397 * Form B := U'*B
398 * where U = P(m)*inv(U(m))* ... *P(1)*inv(U(1))
399 * and U' = inv(U'(1))*P(1)* ... *inv(U'(m))*P(m)
400 *
401  IF( lsame( uplo, 'U' ) ) THEN
402 *
403 * Loop backward applying the transformations.
404 *
405  k = n
406  70 CONTINUE
407  IF( k.LT.1 )
408  \$ GO TO 90
409 *
410 * 1 x 1 pivot block.
411 *
412  IF( ipiv( k ).GT.0 ) THEN
413  IF( k.GT.1 ) THEN
414 *
415 * Interchange if P(K) != I.
416 *
417  kp = ipiv( k )
418  IF( kp.NE.k )
419  \$ CALL zswap( nrhs, b( k, 1 ), ldb, b( kp, 1 ), ldb )
420 *
421 * Apply the transformation
422 *
423  CALL zgemv( 'Transpose', k-1, nrhs, cone, b, ldb,
424  \$ a( 1, k ), 1, cone, b( k, 1 ), ldb )
425  END IF
426  IF( nounit )
427  \$ CALL zscal( nrhs, a( k, k ), b( k, 1 ), ldb )
428  k = k - 1
429 *
430 * 2 x 2 pivot block.
431 *
432  ELSE
433  IF( k.GT.2 ) THEN
434 *
435 * Interchange if P(K) != I.
436 *
437  kp = abs( ipiv( k ) )
438  IF( kp.NE.k-1 )
439  \$ CALL zswap( nrhs, b( k-1, 1 ), ldb, b( kp, 1 ),
440  \$ ldb )
441 *
442 * Apply the transformations
443 *
444  CALL zgemv( 'Transpose', k-2, nrhs, cone, b, ldb,
445  \$ a( 1, k ), 1, cone, b( k, 1 ), ldb )
446  CALL zgemv( 'Transpose', k-2, nrhs, cone, b, ldb,
447  \$ a( 1, k-1 ), 1, cone, b( k-1, 1 ), ldb )
448  END IF
449 *
450 * Multiply by the diagonal block if non-unit.
451 *
452  IF( nounit ) THEN
453  d11 = a( k-1, k-1 )
454  d22 = a( k, k )
455  d12 = a( k-1, k )
456  d21 = d12
457  DO 80 j = 1, nrhs
458  t1 = b( k-1, j )
459  t2 = b( k, j )
460  b( k-1, j ) = d11*t1 + d12*t2
461  b( k, j ) = d21*t1 + d22*t2
462  80 CONTINUE
463  END IF
464  k = k - 2
465  END IF
466  GO TO 70
467  90 CONTINUE
468 *
469 * Form B := L'*B
470 * where L = P(1)*inv(L(1))* ... *P(m)*inv(L(m))
471 * and L' = inv(L'(m))*P(m)* ... *inv(L'(1))*P(1)
472 *
473  ELSE
474 *
475 * Loop forward applying the L-transformations.
476 *
477  k = 1
478  100 CONTINUE
479  IF( k.GT.n )
480  \$ GO TO 120
481 *
482 * 1 x 1 pivot block
483 *
484  IF( ipiv( k ).GT.0 ) THEN
485  IF( k.LT.n ) THEN
486 *
487 * Interchange if P(K) != I.
488 *
489  kp = ipiv( k )
490  IF( kp.NE.k )
491  \$ CALL zswap( nrhs, b( k, 1 ), ldb, b( kp, 1 ), ldb )
492 *
493 * Apply the transformation
494 *
495  CALL zgemv( 'Transpose', n-k, nrhs, cone, b( k+1, 1 ),
496  \$ ldb, a( k+1, k ), 1, cone, b( k, 1 ), ldb )
497  END IF
498  IF( nounit )
499  \$ CALL zscal( nrhs, a( k, k ), b( k, 1 ), ldb )
500  k = k + 1
501 *
502 * 2 x 2 pivot block.
503 *
504  ELSE
505  IF( k.LT.n-1 ) THEN
506 *
507 * Interchange if P(K) != I.
508 *
509  kp = abs( ipiv( k ) )
510  IF( kp.NE.k+1 )
511  \$ CALL zswap( nrhs, b( k+1, 1 ), ldb, b( kp, 1 ),
512  \$ ldb )
513 *
514 * Apply the transformation
515 *
516  CALL zgemv( 'Transpose', n-k-1, nrhs, cone,
517  \$ b( k+2, 1 ), ldb, a( k+2, k+1 ), 1, cone,
518  \$ b( k+1, 1 ), ldb )
519  CALL zgemv( 'Transpose', n-k-1, nrhs, cone,
520  \$ b( k+2, 1 ), ldb, a( k+2, k ), 1, cone,
521  \$ b( k, 1 ), ldb )
522  END IF
523 *
524 * Multiply by the diagonal block if non-unit.
525 *
526  IF( nounit ) THEN
527  d11 = a( k, k )
528  d22 = a( k+1, k+1 )
529  d21 = a( k+1, k )
530  d12 = d21
531  DO 110 j = 1, nrhs
532  t1 = b( k, j )
533  t2 = b( k+1, j )
534  b( k, j ) = d11*t1 + d12*t2
535  b( k+1, j ) = d21*t1 + d22*t2
536  110 CONTINUE
537  END IF
538  k = k + 2
539  END IF
540  GO TO 100
541  120 CONTINUE
542  END IF
543  END IF
544  RETURN
545 *
546 * End of ZLAVSY
547 *
subroutine zgemv(TRANS, M, N, ALPHA, A, LDA, X, INCX, BETA, Y, INCY)
ZGEMV
Definition: zgemv.f:160
subroutine zswap(N, ZX, INCX, ZY, INCY)
ZSWAP
Definition: zswap.f:83
subroutine xerbla(SRNAME, INFO)
XERBLA
Definition: xerbla.f:62
logical function lsame(CA, CB)
LSAME
Definition: lsame.f:55
subroutine zgeru(M, N, ALPHA, X, INCX, Y, INCY, A, LDA)
ZGERU
Definition: zgeru.f:132
subroutine zscal(N, ZA, ZX, INCX)
ZSCAL
Definition: zscal.f:80
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