LAPACK  3.4.2 LAPACK: Linear Algebra PACKage
clavhp.f
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1 *> \brief \b CLAVHP
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 CLAVHP( UPLO, TRANS, DIAG, N, NRHS, A, IPIV, B, LDB,
12 * INFO )
13 *
14 * .. Scalar Arguments ..
15 * CHARACTER DIAG, TRANS, UPLO
16 * INTEGER INFO, LDB, N, NRHS
17 * ..
18 * .. Array Arguments ..
19 * INTEGER IPIV( * )
20 * COMPLEX A( * ), B( LDB, * )
21 * ..
22 *
23 *
24 *> \par Purpose:
25 * =============
26 *>
27 *> \verbatim
28 *>
29 *> CLAVHP performs one of the matrix-vector operations
30 *> x := A*x or x := A^H*x,
31 *> where x is an N element vector and A is one of the factors
32 *> from the symmetric factorization computed by CHPTRF.
33 *> CHPTRF produces a factorization of the form
34 *> U * D * U^H or L * D * L^H,
35 *> where U (or L) is a product of permutation and unit upper (lower)
36 *> triangular matrices, U^H (or L^H) is the conjugate transpose of
37 *> U (or L), and D is Hermitian and block diagonal with 1 x 1 and
38 *> 2 x 2 diagonal blocks. The multipliers for the transformations
39 *> and the upper or lower triangular parts of the diagonal blocks
40 *> are stored columnwise in packed format in the linear array A.
41 *>
42 *> If TRANS = 'N' or 'n', CLAVHP multiplies either by U or U * D
43 *> (or L or L * D).
44 *> If TRANS = 'C' or 'c', CLAVHP multiplies either by U^H or D * U^H
45 *> (or L^H or D * L^H ).
46 *> \endverbatim
47 *
48 * Arguments:
49 * ==========
50 *
51 *> \verbatim
52 *> UPLO - CHARACTER*1
53 *> On entry, UPLO specifies whether the triangular matrix
54 *> stored in A is upper or lower triangular.
55 *> UPLO = 'U' or 'u' The matrix is upper triangular.
56 *> UPLO = 'L' or 'l' The matrix is lower triangular.
57 *> Unchanged on exit.
58 *>
59 *> TRANS - CHARACTER*1
60 *> On entry, TRANS specifies the operation to be performed as
61 *> follows:
62 *> TRANS = 'N' or 'n' x := A*x.
63 *> TRANS = 'C' or 'c' x := A^H*x.
64 *> Unchanged on exit.
65 *>
66 *> DIAG - CHARACTER*1
67 *> On entry, DIAG specifies whether the diagonal blocks are
68 *> assumed to be unit matrices, as follows:
69 *> DIAG = 'U' or 'u' Diagonal blocks are unit matrices.
70 *> DIAG = 'N' or 'n' Diagonal blocks are non-unit.
71 *> Unchanged on exit.
72 *>
73 *> N - INTEGER
74 *> On entry, N specifies the order of the matrix A.
75 *> N must be at least zero.
76 *> Unchanged on exit.
77 *>
78 *> NRHS - INTEGER
79 *> On entry, NRHS specifies the number of right hand sides,
80 *> i.e., the number of vectors x to be multiplied by A.
81 *> NRHS must be at least zero.
82 *> Unchanged on exit.
83 *>
84 *> A - COMPLEX array, dimension( N*(N+1)/2 )
85 *> On entry, A contains a block diagonal matrix and the
86 *> multipliers of the transformations used to obtain it,
87 *> stored as a packed triangular matrix.
88 *> Unchanged on exit.
89 *>
90 *> IPIV - INTEGER array, dimension( N )
91 *> On entry, IPIV contains the vector of pivot indices as
92 *> determined by CSPTRF or CHPTRF.
93 *> If IPIV( K ) = K, no interchange was done.
94 *> If IPIV( K ) <> K but IPIV( K ) > 0, then row K was inter-
95 *> changed with row IPIV( K ) and a 1 x 1 pivot block was used.
96 *> If IPIV( K ) < 0 and UPLO = 'U', then row K-1 was exchanged
97 *> with row | IPIV( K ) | and a 2 x 2 pivot block was used.
98 *> If IPIV( K ) < 0 and UPLO = 'L', then row K+1 was exchanged
99 *> with row | IPIV( K ) | and a 2 x 2 pivot block was used.
100 *>
101 *> B - COMPLEX array, dimension( LDB, NRHS )
102 *> On entry, B contains NRHS vectors of length N.
103 *> On exit, B is overwritten with the product A * B.
104 *>
105 *> LDB - INTEGER
106 *> On entry, LDB contains the leading dimension of B as
107 *> declared in the calling program. LDB must be at least
108 *> max( 1, N ).
109 *> Unchanged on exit.
110 *>
111 *> INFO - INTEGER
112 *> INFO is the error flag.
113 *> On exit, a value of 0 indicates a successful exit.
114 *> A negative value, say -K, indicates that the K-th argument
115 *> has an illegal value.
116 *> \endverbatim
117 *
118 * Authors:
119 * ========
120 *
121 *> \author Univ. of Tennessee
122 *> \author Univ. of California Berkeley
123 *> \author Univ. of Colorado Denver
124 *> \author NAG Ltd.
125 *
126 *> \date November 2011
127 *
128 *> \ingroup complex_lin
129 *
130 * =====================================================================
131  SUBROUTINE clavhp( UPLO, TRANS, DIAG, N, NRHS, A, IPIV, B, LDB,
132  \$ info )
133 *
134 * -- LAPACK test routine (version 3.4.0) --
135 * -- LAPACK is a software package provided by Univ. of Tennessee, --
136 * -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
137 * November 2011
138 *
139 * .. Scalar Arguments ..
140  CHARACTER diag, trans, uplo
141  INTEGER info, ldb, n, nrhs
142 * ..
143 * .. Array Arguments ..
144  INTEGER ipiv( * )
145  COMPLEX a( * ), b( ldb, * )
146 * ..
147 *
148 * =====================================================================
149 *
150 * .. Parameters ..
151  COMPLEX one
152  parameter( one = ( 1.0e+0, 0.0e+0 ) )
153 * ..
154 * .. Local Scalars ..
155  LOGICAL nounit
156  INTEGER j, k, kc, kcnext, kp
157  COMPLEX d11, d12, d21, d22, t1, t2
158 * ..
159 * .. External Functions ..
160  LOGICAL lsame
161  EXTERNAL lsame
162 * ..
163 * .. External Subroutines ..
164  EXTERNAL cgemv, cgeru, clacgv, cscal, cswap, xerbla
165 * ..
166 * .. Intrinsic Functions ..
167  INTRINSIC abs, conjg, max
168 * ..
169 * .. Executable Statements ..
170 *
171 * Test the input parameters.
172 *
173  info = 0
174  IF( .NOT.lsame( uplo, 'U' ) .AND. .NOT.lsame( uplo, 'L' ) ) THEN
175  info = -1
176  ELSE IF( .NOT.lsame( trans, 'N' ) .AND. .NOT.lsame( trans, 'C' ) )
177  \$ THEN
178  info = -2
179  ELSE IF( .NOT.lsame( diag, 'U' ) .AND. .NOT.lsame( diag, 'N' ) )
180  \$ THEN
181  info = -3
182  ELSE IF( n.LT.0 ) THEN
183  info = -4
184  ELSE IF( ldb.LT.max( 1, n ) ) THEN
185  info = -8
186  END IF
187  IF( info.NE.0 ) THEN
188  CALL xerbla( 'CLAVHP ', -info )
189  return
190  END IF
191 *
192 * Quick return if possible.
193 *
194  IF( n.EQ.0 )
195  \$ return
196 *
197  nounit = lsame( diag, 'N' )
198 *------------------------------------------
199 *
200 * Compute B := A * B (No transpose)
201 *
202 *------------------------------------------
203  IF( lsame( trans, 'N' ) ) THEN
204 *
205 * Compute B := U*B
206 * where U = P(m)*inv(U(m))* ... *P(1)*inv(U(1))
207 *
208  IF( lsame( uplo, 'U' ) ) THEN
209 *
210 * Loop forward applying the transformations.
211 *
212  k = 1
213  kc = 1
214  10 continue
215  IF( k.GT.n )
216  \$ go to 30
217 *
218 * 1 x 1 pivot block
219 *
220  IF( ipiv( k ).GT.0 ) THEN
221 *
222 * Multiply by the diagonal element if forming U * D.
223 *
224  IF( nounit )
225  \$ CALL cscal( nrhs, a( kc+k-1 ), b( k, 1 ), ldb )
226 *
227 * Multiply by P(K) * inv(U(K)) if K > 1.
228 *
229  IF( k.GT.1 ) THEN
230 *
231 * Apply the transformation.
232 *
233  CALL cgeru( k-1, nrhs, one, a( kc ), 1, b( k, 1 ),
234  \$ ldb, b( 1, 1 ), ldb )
235 *
236 * Interchange if P(K) != I.
237 *
238  kp = ipiv( k )
239  IF( kp.NE.k )
240  \$ CALL cswap( nrhs, b( k, 1 ), ldb, b( kp, 1 ), ldb )
241  END IF
242  kc = kc + k
243  k = k + 1
244  ELSE
245 *
246 * 2 x 2 pivot block
247 *
248  kcnext = kc + k
249 *
250 * Multiply by the diagonal block if forming U * D.
251 *
252  IF( nounit ) THEN
253  d11 = a( kcnext-1 )
254  d22 = a( kcnext+k )
255  d12 = a( kcnext+k-1 )
256  d21 = conjg( d12 )
257  DO 20 j = 1, nrhs
258  t1 = b( k, j )
259  t2 = b( k+1, j )
260  b( k, j ) = d11*t1 + d12*t2
261  b( k+1, j ) = d21*t1 + d22*t2
262  20 continue
263  END IF
264 *
265 * Multiply by P(K) * inv(U(K)) if K > 1.
266 *
267  IF( k.GT.1 ) THEN
268 *
269 * Apply the transformations.
270 *
271  CALL cgeru( k-1, nrhs, one, a( kc ), 1, b( k, 1 ),
272  \$ ldb, b( 1, 1 ), ldb )
273  CALL cgeru( k-1, nrhs, one, a( kcnext ), 1,
274  \$ b( k+1, 1 ), ldb, b( 1, 1 ), ldb )
275 *
276 * Interchange if P(K) != I.
277 *
278  kp = abs( ipiv( k ) )
279  IF( kp.NE.k )
280  \$ CALL cswap( nrhs, b( k, 1 ), ldb, b( kp, 1 ), ldb )
281  END IF
282  kc = kcnext + k + 1
283  k = k + 2
284  END IF
285  go to 10
286  30 continue
287 *
288 * Compute B := L*B
289 * where L = P(1)*inv(L(1))* ... *P(m)*inv(L(m)) .
290 *
291  ELSE
292 *
293 * Loop backward applying the transformations to B.
294 *
295  k = n
296  kc = n*( n+1 ) / 2 + 1
297  40 continue
298  IF( k.LT.1 )
299  \$ go to 60
300  kc = kc - ( n-k+1 )
301 *
302 * Test the pivot index. If greater than zero, a 1 x 1
303 * pivot was used, otherwise a 2 x 2 pivot was used.
304 *
305  IF( ipiv( k ).GT.0 ) THEN
306 *
307 * 1 x 1 pivot block:
308 *
309 * Multiply by the diagonal element if forming L * D.
310 *
311  IF( nounit )
312  \$ CALL cscal( nrhs, a( kc ), b( k, 1 ), ldb )
313 *
314 * Multiply by P(K) * inv(L(K)) if K < N.
315 *
316  IF( k.NE.n ) THEN
317  kp = ipiv( k )
318 *
319 * Apply the transformation.
320 *
321  CALL cgeru( n-k, nrhs, one, a( kc+1 ), 1, b( k, 1 ),
322  \$ ldb, b( k+1, 1 ), ldb )
323 *
324 * Interchange if a permutation was applied at the
325 * K-th step of the factorization.
326 *
327  IF( kp.NE.k )
328  \$ CALL cswap( nrhs, b( k, 1 ), ldb, b( kp, 1 ), ldb )
329  END IF
330  k = k - 1
331 *
332  ELSE
333 *
334 * 2 x 2 pivot block:
335 *
336  kcnext = kc - ( n-k+2 )
337 *
338 * Multiply by the diagonal block if forming L * D.
339 *
340  IF( nounit ) THEN
341  d11 = a( kcnext )
342  d22 = a( kc )
343  d21 = a( kcnext+1 )
344  d12 = conjg( d21 )
345  DO 50 j = 1, nrhs
346  t1 = b( k-1, j )
347  t2 = b( k, j )
348  b( k-1, j ) = d11*t1 + d12*t2
349  b( k, j ) = d21*t1 + d22*t2
350  50 continue
351  END IF
352 *
353 * Multiply by P(K) * inv(L(K)) if K < N.
354 *
355  IF( k.NE.n ) THEN
356 *
357 * Apply the transformation.
358 *
359  CALL cgeru( n-k, nrhs, one, a( kc+1 ), 1, b( k, 1 ),
360  \$ ldb, b( k+1, 1 ), ldb )
361  CALL cgeru( n-k, nrhs, one, a( kcnext+2 ), 1,
362  \$ b( k-1, 1 ), ldb, b( k+1, 1 ), ldb )
363 *
364 * Interchange if a permutation was applied at the
365 * K-th step of the factorization.
366 *
367  kp = abs( ipiv( k ) )
368  IF( kp.NE.k )
369  \$ CALL cswap( nrhs, b( k, 1 ), ldb, b( kp, 1 ), ldb )
370  END IF
371  kc = kcnext
372  k = k - 2
373  END IF
374  go to 40
375  60 continue
376  END IF
377 *-------------------------------------------------
378 *
379 * Compute B := A^H * B (conjugate transpose)
380 *
381 *-------------------------------------------------
382  ELSE
383 *
384 * Form B := U^H*B
385 * where U = P(m)*inv(U(m))* ... *P(1)*inv(U(1))
386 * and U^H = inv(U^H(1))*P(1)* ... *inv(U^H(m))*P(m)
387 *
388  IF( lsame( uplo, 'U' ) ) THEN
389 *
390 * Loop backward applying the transformations.
391 *
392  k = n
393  kc = n*( n+1 ) / 2 + 1
394  70 IF( k.LT.1 )
395  \$ go to 90
396  kc = kc - k
397 *
398 * 1 x 1 pivot block.
399 *
400  IF( ipiv( k ).GT.0 ) THEN
401  IF( k.GT.1 ) THEN
402 *
403 * Interchange if P(K) != I.
404 *
405  kp = ipiv( k )
406  IF( kp.NE.k )
407  \$ CALL cswap( nrhs, b( k, 1 ), ldb, b( kp, 1 ), ldb )
408 *
409 * Apply the transformation:
410 * y := y - B' * conjg(x)
411 * where x is a column of A and y is a row of B.
412 *
413  CALL clacgv( nrhs, b( k, 1 ), ldb )
414  CALL cgemv( 'Conjugate', k-1, nrhs, one, b, ldb,
415  \$ a( kc ), 1, one, b( k, 1 ), ldb )
416  CALL clacgv( nrhs, b( k, 1 ), ldb )
417  END IF
418  IF( nounit )
419  \$ CALL cscal( nrhs, a( kc+k-1 ), b( k, 1 ), ldb )
420  k = k - 1
421 *
422 * 2 x 2 pivot block.
423 *
424  ELSE
425  kcnext = kc - ( k-1 )
426  IF( k.GT.2 ) THEN
427 *
428 * Interchange if P(K) != I.
429 *
430  kp = abs( ipiv( k ) )
431  IF( kp.NE.k-1 )
432  \$ CALL cswap( nrhs, b( k-1, 1 ), ldb, b( kp, 1 ),
433  \$ ldb )
434 *
435 * Apply the transformations.
436 *
437  CALL clacgv( nrhs, b( k, 1 ), ldb )
438  CALL cgemv( 'Conjugate', k-2, nrhs, one, b, ldb,
439  \$ a( kc ), 1, one, b( k, 1 ), ldb )
440  CALL clacgv( nrhs, b( k, 1 ), ldb )
441 *
442  CALL clacgv( nrhs, b( k-1, 1 ), ldb )
443  CALL cgemv( 'Conjugate', k-2, nrhs, one, b, ldb,
444  \$ a( kcnext ), 1, one, b( k-1, 1 ), ldb )
445  CALL clacgv( nrhs, b( k-1, 1 ), ldb )
446  END IF
447 *
448 * Multiply by the diagonal block if non-unit.
449 *
450  IF( nounit ) THEN
451  d11 = a( kc-1 )
452  d22 = a( kc+k-1 )
453  d12 = a( kc+k-2 )
454  d21 = conjg( d12 )
455  DO 80 j = 1, nrhs
456  t1 = b( k-1, j )
457  t2 = b( k, j )
458  b( k-1, j ) = d11*t1 + d12*t2
459  b( k, j ) = d21*t1 + d22*t2
460  80 continue
461  END IF
462  kc = kcnext
463  k = k - 2
464  END IF
465  go to 70
466  90 continue
467 *
468 * Form B := L^H*B
469 * where L = P(1)*inv(L(1))* ... *P(m)*inv(L(m))
470 * and L^H = inv(L(m))*P(m)* ... *inv(L(1))*P(1)
471 *
472  ELSE
473 *
474 * Loop forward applying the L-transformations.
475 *
476  k = 1
477  kc = 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 cswap( nrhs, b( k, 1 ), ldb, b( kp, 1 ), ldb )
492 *
493 * Apply the transformation
494 *
495  CALL clacgv( nrhs, b( k, 1 ), ldb )
496  CALL cgemv( 'Conjugate', n-k, nrhs, one, b( k+1, 1 ),
497  \$ ldb, a( kc+1 ), 1, one, b( k, 1 ), ldb )
498  CALL clacgv( nrhs, b( k, 1 ), ldb )
499  END IF
500  IF( nounit )
501  \$ CALL cscal( nrhs, a( kc ), b( k, 1 ), ldb )
502  kc = kc + n - k + 1
503  k = k + 1
504 *
505 * 2 x 2 pivot block.
506 *
507  ELSE
508  kcnext = kc + n - k + 1
509  IF( k.LT.n-1 ) THEN
510 *
511 * Interchange if P(K) != I.
512 *
513  kp = abs( ipiv( k ) )
514  IF( kp.NE.k+1 )
515  \$ CALL cswap( nrhs, b( k+1, 1 ), ldb, b( kp, 1 ),
516  \$ ldb )
517 *
518 * Apply the transformation
519 *
520  CALL clacgv( nrhs, b( k+1, 1 ), ldb )
521  CALL cgemv( 'Conjugate', n-k-1, nrhs, one,
522  \$ b( k+2, 1 ), ldb, a( kcnext+1 ), 1, one,
523  \$ b( k+1, 1 ), ldb )
524  CALL clacgv( nrhs, b( k+1, 1 ), ldb )
525 *
526  CALL clacgv( nrhs, b( k, 1 ), ldb )
527  CALL cgemv( 'Conjugate', n-k-1, nrhs, one,
528  \$ b( k+2, 1 ), ldb, a( kc+2 ), 1, one,
529  \$ b( k, 1 ), ldb )
530  CALL clacgv( nrhs, b( k, 1 ), ldb )
531  END IF
532 *
533 * Multiply by the diagonal block if non-unit.
534 *
535  IF( nounit ) THEN
536  d11 = a( kc )
537  d22 = a( kcnext )
538  d21 = a( kc+1 )
539  d12 = conjg( d21 )
540  DO 110 j = 1, nrhs
541  t1 = b( k, j )
542  t2 = b( k+1, j )
543  b( k, j ) = d11*t1 + d12*t2
544  b( k+1, j ) = d21*t1 + d22*t2
545  110 continue
546  END IF
547  kc = kcnext + ( n-k )
548  k = k + 2
549  END IF
550  go to 100
551  120 continue
552  END IF
553 *
554  END IF
555  return
556 *
557 * End of CLAVHP
558 *
559  END