LAPACK  3.6.1 LAPACK: Linear Algebra PACKage
 subroutine zhpgvx ( integer ITYPE, character JOBZ, character RANGE, character UPLO, integer N, complex*16, dimension( * ) AP, complex*16, dimension( * ) BP, double precision VL, double precision VU, integer IL, integer IU, double precision ABSTOL, integer M, double precision, dimension( * ) W, complex*16, dimension( ldz, * ) Z, integer LDZ, complex*16, dimension( * ) WORK, double precision, dimension( * ) RWORK, integer, dimension( * ) IWORK, integer, dimension( * ) IFAIL, integer INFO )

ZHPGVX

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Purpose:
``` ZHPGVX computes selected eigenvalues and, optionally, eigenvectors
of a complex generalized Hermitian-definite eigenproblem, of the form
A*x=(lambda)*B*x,  A*Bx=(lambda)*x,  or B*A*x=(lambda)*x.  Here A and
B are assumed to be Hermitian, stored in packed format, and B is also
positive definite.  Eigenvalues and eigenvectors can be selected by
specifying either a range of values or a range of indices for the
desired eigenvalues.```
Parameters
 [in] ITYPE ``` ITYPE is INTEGER Specifies the problem type to be solved: = 1: A*x = (lambda)*B*x = 2: A*B*x = (lambda)*x = 3: B*A*x = (lambda)*x``` [in] JOBZ ``` JOBZ is CHARACTER*1 = 'N': Compute eigenvalues only; = 'V': Compute eigenvalues and eigenvectors.``` [in] RANGE ``` RANGE is CHARACTER*1 = 'A': all eigenvalues will be found; = 'V': all eigenvalues in the half-open interval (VL,VU] will be found; = 'I': the IL-th through IU-th eigenvalues will be found.``` [in] UPLO ``` UPLO is CHARACTER*1 = 'U': Upper triangles of A and B are stored; = 'L': Lower triangles of A and B are stored.``` [in] N ``` N is INTEGER The order of the matrices A and B. N >= 0.``` [in,out] AP ``` AP is COMPLEX*16 array, dimension (N*(N+1)/2) On entry, the upper or lower triangle of the Hermitian matrix A, packed columnwise in a linear array. The j-th column of A is stored in the array AP as follows: if UPLO = 'U', AP(i + (j-1)*j/2) = A(i,j) for 1<=i<=j; if UPLO = 'L', AP(i + (j-1)*(2*n-j)/2) = A(i,j) for j<=i<=n. On exit, the contents of AP are destroyed.``` [in,out] BP ``` BP is COMPLEX*16 array, dimension (N*(N+1)/2) On entry, the upper or lower triangle of the Hermitian matrix B, packed columnwise in a linear array. The j-th column of B is stored in the array BP as follows: if UPLO = 'U', BP(i + (j-1)*j/2) = B(i,j) for 1<=i<=j; if UPLO = 'L', BP(i + (j-1)*(2*n-j)/2) = B(i,j) for j<=i<=n. On exit, the triangular factor U or L from the Cholesky factorization B = U**H*U or B = L*L**H, in the same storage format as B.``` [in] VL ``` VL is DOUBLE PRECISION If RANGE='V', the lower bound of the interval to be searched for eigenvalues. VL < VU. Not referenced if RANGE = 'A' or 'I'.``` [in] VU ``` VU is DOUBLE PRECISION If RANGE='V', the upper bound of the interval to be searched for eigenvalues. VL < VU. Not referenced if RANGE = 'A' or 'I'.``` [in] IL ``` IL is INTEGER If RANGE='I', the index of the smallest eigenvalue to be returned. 1 <= IL <= IU <= N, if N > 0; IL = 1 and IU = 0 if N = 0. Not referenced if RANGE = 'A' or 'V'.``` [in] IU ``` IU is INTEGER If RANGE='I', the index of the largest eigenvalue to be returned. 1 <= IL <= IU <= N, if N > 0; IL = 1 and IU = 0 if N = 0. Not referenced if RANGE = 'A' or 'V'.``` [in] ABSTOL ``` ABSTOL is DOUBLE PRECISION The absolute error tolerance for the eigenvalues. An approximate eigenvalue is accepted as converged when it is determined to lie in an interval [a,b] of width less than or equal to ABSTOL + EPS * max( |a|,|b| ) , where EPS is the machine precision. If ABSTOL is less than or equal to zero, then EPS*|T| will be used in its place, where |T| is the 1-norm of the tridiagonal matrix obtained by reducing AP to tridiagonal form. Eigenvalues will be computed most accurately when ABSTOL is set to twice the underflow threshold 2*DLAMCH('S'), not zero. If this routine returns with INFO>0, indicating that some eigenvectors did not converge, try setting ABSTOL to 2*DLAMCH('S').``` [out] M ``` M is INTEGER The total number of eigenvalues found. 0 <= M <= N. If RANGE = 'A', M = N, and if RANGE = 'I', M = IU-IL+1.``` [out] W ``` W is DOUBLE PRECISION array, dimension (N) On normal exit, the first M elements contain the selected eigenvalues in ascending order.``` [out] Z ``` Z is COMPLEX*16 array, dimension (LDZ, N) If JOBZ = 'N', then Z is not referenced. If JOBZ = 'V', then if INFO = 0, the first M columns of Z contain the orthonormal eigenvectors of the matrix A corresponding to the selected eigenvalues, with the i-th column of Z holding the eigenvector associated with W(i). The eigenvectors are normalized as follows: if ITYPE = 1 or 2, Z**H*B*Z = I; if ITYPE = 3, Z**H*inv(B)*Z = I. If an eigenvector fails to converge, then that column of Z contains the latest approximation to the eigenvector, and the index of the eigenvector is returned in IFAIL. Note: the user must ensure that at least max(1,M) columns are supplied in the array Z; if RANGE = 'V', the exact value of M is not known in advance and an upper bound must be used.``` [in] LDZ ``` LDZ is INTEGER The leading dimension of the array Z. LDZ >= 1, and if JOBZ = 'V', LDZ >= max(1,N).``` [out] WORK ` WORK is COMPLEX*16 array, dimension (2*N)` [out] RWORK ` RWORK is DOUBLE PRECISION array, dimension (7*N)` [out] IWORK ` IWORK is INTEGER array, dimension (5*N)` [out] IFAIL ``` IFAIL is INTEGER array, dimension (N) If JOBZ = 'V', then if INFO = 0, the first M elements of IFAIL are zero. If INFO > 0, then IFAIL contains the indices of the eigenvectors that failed to converge. If JOBZ = 'N', then IFAIL is not referenced.``` [out] INFO ``` INFO is INTEGER = 0: successful exit < 0: if INFO = -i, the i-th argument had an illegal value > 0: ZPPTRF or ZHPEVX returned an error code: <= N: if INFO = i, ZHPEVX failed to converge; i eigenvectors failed to converge. Their indices are stored in array IFAIL. > N: if INFO = N + i, for 1 <= i <= n, then the leading minor of order i of B is not positive definite. The factorization of B could not be completed and no eigenvalues or eigenvectors were computed.```
Date
June 2016
Contributors:
Mark Fahey, Department of Mathematics, Univ. of Kentucky, USA

Definition at line 279 of file zhpgvx.f.

279 *
280 * -- LAPACK driver routine (version 3.6.1) --
281 * -- LAPACK is a software package provided by Univ. of Tennessee, --
282 * -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
283 * June 2016
284 *
285 * .. Scalar Arguments ..
286  CHARACTER jobz, range, uplo
287  INTEGER il, info, itype, iu, ldz, m, n
288  DOUBLE PRECISION abstol, vl, vu
289 * ..
290 * .. Array Arguments ..
291  INTEGER ifail( * ), iwork( * )
292  DOUBLE PRECISION rwork( * ), w( * )
293  COMPLEX*16 ap( * ), bp( * ), work( * ), z( ldz, * )
294 * ..
295 *
296 * =====================================================================
297 *
298 * .. Local Scalars ..
299  LOGICAL alleig, indeig, upper, valeig, wantz
300  CHARACTER trans
301  INTEGER j
302 * ..
303 * .. External Functions ..
304  LOGICAL lsame
305  EXTERNAL lsame
306 * ..
307 * .. External Subroutines ..
308  EXTERNAL xerbla, zhpevx, zhpgst, zpptrf, ztpmv, ztpsv
309 * ..
310 * .. Intrinsic Functions ..
311  INTRINSIC min
312 * ..
313 * .. Executable Statements ..
314 *
315 * Test the input parameters.
316 *
317  wantz = lsame( jobz, 'V' )
318  upper = lsame( uplo, 'U' )
319  alleig = lsame( range, 'A' )
320  valeig = lsame( range, 'V' )
321  indeig = lsame( range, 'I' )
322 *
323  info = 0
324  IF( itype.LT.1 .OR. itype.GT.3 ) THEN
325  info = -1
326  ELSE IF( .NOT.( wantz .OR. lsame( jobz, 'N' ) ) ) THEN
327  info = -2
328  ELSE IF( .NOT.( alleig .OR. valeig .OR. indeig ) ) THEN
329  info = -3
330  ELSE IF( .NOT.( upper .OR. lsame( uplo, 'L' ) ) ) THEN
331  info = -4
332  ELSE IF( n.LT.0 ) THEN
333  info = -5
334  ELSE
335  IF( valeig ) THEN
336  IF( n.GT.0 .AND. vu.LE.vl ) THEN
337  info = -9
338  END IF
339  ELSE IF( indeig ) THEN
340  IF( il.LT.1 ) THEN
341  info = -10
342  ELSE IF( iu.LT.min( n, il ) .OR. iu.GT.n ) THEN
343  info = -11
344  END IF
345  END IF
346  END IF
347  IF( info.EQ.0 ) THEN
348  IF( ldz.LT.1 .OR. ( wantz .AND. ldz.LT.n ) ) THEN
349  info = -16
350  END IF
351  END IF
352 *
353  IF( info.NE.0 ) THEN
354  CALL xerbla( 'ZHPGVX', -info )
355  RETURN
356  END IF
357 *
358 * Quick return if possible
359 *
360  IF( n.EQ.0 )
361  \$ RETURN
362 *
363 * Form a Cholesky factorization of B.
364 *
365  CALL zpptrf( uplo, n, bp, info )
366  IF( info.NE.0 ) THEN
367  info = n + info
368  RETURN
369  END IF
370 *
371 * Transform problem to standard eigenvalue problem and solve.
372 *
373  CALL zhpgst( itype, uplo, n, ap, bp, info )
374  CALL zhpevx( jobz, range, uplo, n, ap, vl, vu, il, iu, abstol, m,
375  \$ w, z, ldz, work, rwork, iwork, ifail, info )
376 *
377  IF( wantz ) THEN
378 *
379 * Backtransform eigenvectors to the original problem.
380 *
381  IF( info.GT.0 )
382  \$ m = info - 1
383  IF( itype.EQ.1 .OR. itype.EQ.2 ) THEN
384 *
385 * For A*x=(lambda)*B*x and A*B*x=(lambda)*x;
386 * backtransform eigenvectors: x = inv(L)**H *y or inv(U)*y
387 *
388  IF( upper ) THEN
389  trans = 'N'
390  ELSE
391  trans = 'C'
392  END IF
393 *
394  DO 10 j = 1, m
395  CALL ztpsv( uplo, trans, 'Non-unit', n, bp, z( 1, j ),
396  \$ 1 )
397  10 CONTINUE
398 *
399  ELSE IF( itype.EQ.3 ) THEN
400 *
401 * For B*A*x=(lambda)*x;
402 * backtransform eigenvectors: x = L*y or U**H *y
403 *
404  IF( upper ) THEN
405  trans = 'C'
406  ELSE
407  trans = 'N'
408  END IF
409 *
410  DO 20 j = 1, m
411  CALL ztpmv( uplo, trans, 'Non-unit', n, bp, z( 1, j ),
412  \$ 1 )
413  20 CONTINUE
414  END IF
415  END IF
416 *
417  RETURN
418 *
419 * End of ZHPGVX
420 *
subroutine xerbla(SRNAME, INFO)
XERBLA
Definition: xerbla.f:62
subroutine ztpsv(UPLO, TRANS, DIAG, N, AP, X, INCX)
ZTPSV
Definition: ztpsv.f:146
subroutine ztpmv(UPLO, TRANS, DIAG, N, AP, X, INCX)
ZTPMV
Definition: ztpmv.f:144
subroutine zhpevx(JOBZ, RANGE, UPLO, N, AP, VL, VU, IL, IU, ABSTOL, M, W, Z, LDZ, WORK, RWORK, IWORK, IFAIL, INFO)
ZHPEVX computes the eigenvalues and, optionally, the left and/or right eigenvectors for OTHER matric...
Definition: zhpevx.f:242
logical function lsame(CA, CB)
LSAME
Definition: lsame.f:55
subroutine zpptrf(UPLO, N, AP, INFO)
ZPPTRF
Definition: zpptrf.f:121
subroutine zhpgst(ITYPE, UPLO, N, AP, BP, INFO)
ZHPGST
Definition: zhpgst.f:115

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