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SUBROUTINE PCHEEV( JOBZ, UPLO, N, A, IA, JA, DESCA, W, Z, IZ, JZ,
$ DESCZ, WORK, LWORK, RWORK, LRWORK, INFO )
*
* -- ScaLAPACK routine (version 1.7) --
* University of Tennessee, Knoxville, Oak Ridge National Laboratory,
* and University of California, Berkeley.
* August 14, 2001
*
* .. Scalar Arguments ..
CHARACTER JOBZ, UPLO
INTEGER IA, INFO, IZ, JA, JZ, LRWORK, LWORK, N
* ..
* .. Array Arguments ..
INTEGER DESCA( * ), DESCZ( * )
REAL RWORK( * ), W( * )
COMPLEX A( * ), WORK( * ), Z( * )
* ..
*
* Purpose
* =======
*
* PCHEEV computes selected eigenvalues and, optionally, eigenvectors
* of a real Hermitian matrix A by calling the recommended sequence
* of ScaLAPACK routines.
*
* In its present form, PCHEEV assumes a homogeneous system and makes
* only spot checks of the consistency of the eigenvalues across the
* different processes. Because of this, it is possible that a
* heterogeneous system may return incorrect results without any error
* messages.
*
* Notes
* =====
* A description vector is associated with each 2D block-cyclicly dis-
* tributed matrix. This vector stores the information required to
* establish the mapping between a matrix entry and its corresponding
* process and memory location.
*
* In the following comments, the character _ should be read as
* "of the distributed matrix". Let A be a generic term for any 2D
* block cyclicly distributed matrix. Its description vector is DESCA:
*
* NOTATION STORED IN EXPLANATION
* --------------- -------------- --------------------------------------
* DTYPE_A(global) DESCA( DTYPE_) The descriptor type.
* CTXT_A (global) DESCA( CTXT_ ) The BLACS context handle, indicating
* the BLACS process grid A is distribu-
* ted over. The context itself is glo-
* bal, but the handle (the integer
* value) may vary.
* M_A (global) DESCA( M_ ) The number of rows in the distributed
* matrix A.
* N_A (global) DESCA( N_ ) The number of columns in the distri-
* buted matrix A.
* MB_A (global) DESCA( MB_ ) The blocking factor used to distribute
* the rows of A.
* NB_A (global) DESCA( NB_ ) The blocking factor used to distribute
* the columns of A.
* RSRC_A (global) DESCA( RSRC_ ) The process row over which the first
* row of the matrix A is distributed.
* CSRC_A (global) DESCA( CSRC_ ) The process column over which the
* first column of A is distributed.
* LLD_A (local) DESCA( LLD_ ) The leading dimension of the local
* array storing the local blocks of the
* distributed matrix A.
* LLD_A >= MAX(1,LOCr(M_A)).
*
* Let K be the number of rows or columns of a distributed matrix,
* and assume that its process grid has dimension p x q.
* LOCr( K ) denotes the number of elements of K that a process
* would receive if K were distributed over the p processes of its
* process column.
* Similarly, LOCc( K ) denotes the number of elements of K that a
* process would receive if K were distributed over the q processes of
* its process row.
* The values of LOCr() and LOCc() may be determined via a call to the
* ScaLAPACK tool function, NUMROC:
* LOCr( M ) = NUMROC( M, MB_A, MYROW, RSRC_A, NPROW ),
* LOCc( N ) = NUMROC( N, NB_A, MYCOL, CSRC_A, NPCOL ).
*
* Arguments
* =========
*
* NP = the number of rows local to a given process.
* NQ = the number of columns local to a given process.
*
* JOBZ (global input) CHARACTER*1
* Specifies whether or not to compute the eigenvectors:
* = 'N': Compute eigenvalues only.
* = 'V': Compute eigenvalues and eigenvectors.
*
* UPLO (global input) CHARACTER*1
* Specifies whether the upper or lower triangular part of the
* Hermitian matrix A is stored:
* = 'U': Upper triangular
* = 'L': Lower triangular
*
* N (global input) INTEGER
* The number of rows and columns of the matrix A. N >= 0.
*
* A (local input/workspace) block cyclic COMPLEX array,
* global dimension (N, N), local dimension ( LLD_A,
* LOCc(JA+N-1) )
*
* On entry, the Hermitian matrix A. If UPLO = 'U', only the
* upper triangular part of A is used to define the elements of
* the Hermitian matrix. If UPLO = 'L', only the lower
* triangular part of A is used to define the elements of the
* Hermitian matrix.
*
* On exit, the lower triangle (if UPLO='L') or the upper
* triangle (if UPLO='U') of A, including the diagonal, is
* destroyed.
*
* IA (global input) INTEGER
* A's global row index, which points to the beginning of the
* submatrix which is to be operated on.
*
* JA (global input) INTEGER
* A's global column index, which points to the beginning of
* the submatrix which is to be operated on.
*
* DESCA (global and local input) INTEGER array of dimension DLEN_.
* The array descriptor for the distributed matrix A.
* If DESCA( CTXT_ ) is incorrect, PCHEEV cannot guarantee
* correct error reporting.
*
* W (global output) REAL array, dimension (N)
* If INFO=0, the eigenvalues in ascending order.
*
* Z (local output) COMPLEX array,
* global dimension (N, N),
* local dimension (LLD_Z, LOCc(JZ+N-1))
* If JOBZ = 'V', then on normal exit the first M columns of Z
* contain the orthonormal eigenvectors of the matrix
* corresponding to the selected eigenvalues.
* If JOBZ = 'N', then Z is not referenced.
*
* IZ (global input) INTEGER
* Z's global row index, which points to the beginning of the
* submatrix which is to be operated on.
*
* JZ (global input) INTEGER
* Z's global column index, which points to the beginning of
* the submatrix which is to be operated on.
*
* DESCZ (global and local input) INTEGER array of dimension DLEN_.
* The array descriptor for the distributed matrix Z.
* DESCZ( CTXT_ ) must equal DESCA( CTXT_ )
*
* WORK (local workspace/output) COMPLEX array,
* dimension (LWORK)
* On output, WORK(1) returns the workspace needed to guarantee
* completion. If the input parameters are incorrect, WORK(1)
* may also be incorrect.
*
* If JOBZ='N' WORK(1) = minimal workspace for eigenvalues only.
* If JOBZ='V' WORK(1) = minimal workspace required to
* generate all the eigenvectors.
*
*
* LWORK (local input) INTEGER
* See below for definitions of variables used to define LWORK.
* If no eigenvectors are requested (JOBZ = 'N') then
* LWORK >= MAX( NB*( NP0+1 ), 3 ) +3*N
* If eigenvectors are requested (JOBZ = 'V' ) then
* the amount of workspace required:
* LWORK >= (NP0 + NQ0 + NB)*NB + 3*N + N^2
*
* Variable definitions:
* NB = DESCA( MB_ ) = DESCA( NB_ ) =
* DESCZ( MB_ ) = DESCZ( NB_ )
* NP0 = NUMROC( NN, NB, 0, 0, NPROW )
* NQ0 = NUMROC( MAX( N, NB, 2 ), NB, 0, 0, NPCOL )
*
* If LWORK = -1, the LWORK is global input and a workspace
* query is assumed; the routine only calculates the minimum
* size for the WORK array. The required workspace is returned
* as the first element of WORK and no error message is issued
* by PXERBLA.
*
* RWORK (local workspace/output) COMPLEX array,
* dimension (LRWORK)
* On output RWORK(1) returns the
* REAL workspace needed to
* guarantee completion. If the input parameters are incorrect,
* RWORK(1) may also be incorrect.
*
* LRWORK (local input) INTEGER
* Size of RWORK array.
* If eigenvectors are desired (JOBZ = 'V') then
* LRWORK >= 2*N + 2*N-2
* If eigenvectors are not desired (JOBZ = 'N') then
* LRWORK >= 2*N
*
* If LRWORK = -1, the LRWORK is global input and a workspace
* query is assumed; the routine only calculates the minimum
* size for the RWORK array. The required workspace is returned
* as the first element of RWORK and no error message is issued
* by PXERBLA.
*
* INFO (global output) INTEGER
* = 0: successful exit
* < 0: If the i-th argument is an array and the j-entry had
* an illegal value, then INFO = -(i*100+j), if the i-th
* argument is a scalar and had an illegal value, then
* INFO = -i.
* > 0: If INFO = 1 through N, the i(th) eigenvalue did not
* converge in CSTEQR2 after a total of 30*N iterations.
* If INFO = N+1, then PCHEEV has detected heterogeneity
* by finding that eigenvalues were not identical across
* the process grid. In this case, the accuracy of
* the results from PCHEEV cannot be guaranteed.
*
* Alignment requirements
* ======================
*
* The distributed submatrices A(IA:*, JA:*) and C(IC:IC+M-1,JC:JC+N-1)
* must verify some alignment properties, namely the following
* expressions should be true:
*
* ( MB_A.EQ.NB_A.EQ.MB_Z .AND. IROFFA.EQ.IROFFZ .AND. IROFFA.EQ.0 .AND.
* IAROW.EQ.IZROW )
* where
* IROFFA = MOD( IA-1, MB_A ) and ICOFFA = MOD( JA-1, NB_A ).
*
* =====================================================================
*
* Version 1.4 limitations:
* DESCA(MB_) = DESCA(NB_)
* DESCA(M_) = DESCZ(M_)
* DESCA(N_) = DESCZ(N_)
* DESCA(MB_) = DESCZ(MB_)
* DESCA(NB_) = DESCZ(NB_)
* DESCA(RSRC_) = DESCZ(RSRC_)
*
* .. Parameters ..
INTEGER BLOCK_CYCLIC_2D, DLEN_, DTYPE_, CTXT_, M_, N_,
$ MB_, NB_, RSRC_, CSRC_, LLD_
PARAMETER ( BLOCK_CYCLIC_2D = 1, DLEN_ = 9, DTYPE_ = 1,
$ CTXT_ = 2, M_ = 3, N_ = 4, MB_ = 5, NB_ = 6,
$ RSRC_ = 7, CSRC_ = 8, LLD_ = 9 )
REAL ZERO, ONE
PARAMETER ( ZERO = 0.0E+0, ONE = 1.0E+0 )
COMPLEX CZERO, CONE
PARAMETER ( CZERO = ( 0.0E+0, 0.0E+0 ),
$ CONE = ( 1.0E+0, 0.0E+0 ) )
INTEGER ITHVAL
PARAMETER ( ITHVAL = 10 )
* ..
* .. Local Scalars ..
LOGICAL LOWER, WANTZ
INTEGER CONTEXTC, CSRC_A, I, IACOL, IAROW, ICOFFA,
$ IINFO, INDD, INDE, INDRD, INDRE, INDRWORK,
$ INDTAU, INDWORK, INDWORK2, IROFFA, IROFFZ,
$ ISCALE, IZROW, J, K, LDC, LLRWORK, LLWORK,
$ LRMIN, LRWMIN, LWMIN, MB_A, MB_Z, MYCOL,
$ MYPCOLC, MYPROWC, MYROW, NB, NB_A, NB_Z, NP0,
$ NPCOL, NPCOLC, NPROCS, NPROW, NPROWC, NQ0, NRC,
$ RSIZECSTEQR2, RSRC_A, RSRC_Z, SIZECSTEQR2,
$ SIZEPCHETRD, SIZEPCUNMTR
REAL ANRM, BIGNUM, EPS, RMAX, RMIN, SAFMIN, SIGMA,
$ SMLNUM
* ..
* .. Local Arrays ..
INTEGER DESCQR( 10 ), IDUM1( 3 ), IDUM2( 3 )
* ..
* .. External Functions ..
LOGICAL LSAME
INTEGER INDXG2P, NUMROC, SL_GRIDRESHAPE
REAL PCLANHE, PSLAMCH
EXTERNAL LSAME, INDXG2P, NUMROC, SL_GRIDRESHAPE,
$ PCLANHE, PSLAMCH
* ..
* .. External Subroutines ..
EXTERNAL BLACS_GRIDEXIT, BLACS_GRIDINFO, CHK1MAT,
$ CSTEQR2, DESCINIT, PCELGET, PCGEMR2D, PCHETRD,
$ PCHK1MAT, PCHK2MAT, PCLASCL, PCLASET, PCUNMTR,
$ PXERBLA, SCOPY, SGAMN2D, SGAMX2D, SSCAL
* ..
* .. Intrinsic Functions ..
INTRINSIC ABS, CMPLX, ICHAR, INT, MAX, MIN, MOD, REAL,
$ SQRT
* ..
* .. Executable Statements ..
* This is just to keep ftnchek and toolpack/1 happy
IF( BLOCK_CYCLIC_2D*CSRC_*CTXT_*DLEN_*DTYPE_*LLD_*MB_*M_*NB_*N_*
$ RSRC_.LT.0 )RETURN
*
* Quick return
*
IF( N.EQ.0 )
$ RETURN
*
* Test the input arguments.
*
CALL BLACS_GRIDINFO( DESCA( CTXT_ ), NPROW, NPCOL, MYROW, MYCOL )
INFO = 0
*
* Initialize pointer to some safe value
*
INDTAU = 1
INDD = 1
INDE = 1
INDWORK = 1
INDWORK2 = 1
*
INDRE = 1
INDRD = 1
INDRWORK = 1
*
WANTZ = LSAME( JOBZ, 'V' )
IF( NPROW.EQ.-1 ) THEN
INFO = -( 700+CTXT_ )
ELSE IF( WANTZ ) THEN
IF( DESCA( CTXT_ ).NE.DESCZ( CTXT_ ) ) THEN
INFO = -( 1200+CTXT_ )
END IF
END IF
IF( INFO.EQ.0 ) THEN
CALL CHK1MAT( N, 3, N, 3, IA, JA, DESCA, 7, INFO )
IF( WANTZ )
$ CALL CHK1MAT( N, 3, N, 3, IZ, JZ, DESCZ, 12, INFO )
*
IF( INFO.EQ.0 ) THEN
*
* Get machine constants.
*
SAFMIN = PSLAMCH( DESCA( CTXT_ ), 'Safe minimum' )
EPS = PSLAMCH( DESCA( CTXT_ ), 'Precision' )
SMLNUM = SAFMIN / EPS
BIGNUM = ONE / SMLNUM
RMIN = SQRT( SMLNUM )
RMAX = MIN( SQRT( BIGNUM ), ONE / SQRT( SQRT( SAFMIN ) ) )
*
NPROCS = NPROW*NPCOL
NB_A = DESCA( NB_ )
MB_A = DESCA( MB_ )
NB = NB_A
LOWER = LSAME( UPLO, 'L' )
*
RSRC_A = DESCA( RSRC_ )
CSRC_A = DESCA( CSRC_ )
IROFFA = MOD( IA-1, MB_A )
ICOFFA = MOD( JA-1, NB_A )
IAROW = INDXG2P( 1, NB_A, MYROW, RSRC_A, NPROW )
IACOL = INDXG2P( 1, MB_A, MYCOL, CSRC_A, NPCOL )
NP0 = NUMROC( N+IROFFA, NB, MYROW, IAROW, NPROW )
NQ0 = NUMROC( N+ICOFFA, NB, MYCOL, IACOL, NPCOL )
IF( WANTZ ) THEN
NB_Z = DESCZ( NB_ )
MB_Z = DESCZ( MB_ )
RSRC_Z = DESCZ( RSRC_ )
IROFFZ = MOD( IZ-1, MB_A )
IZROW = INDXG2P( 1, NB_A, MYROW, RSRC_Z, NPROW )
ELSE
IROFFZ = 0
IZROW = 0
END IF
*
* COMPLEX work space for PCHETRD
*
CALL PCHETRD( UPLO, N, A, IA, JA, DESCA, RWORK( INDD ),
$ RWORK( INDE ), WORK( INDTAU ),
$ WORK( INDWORK ), -1, IINFO )
SIZEPCHETRD = INT( ABS( WORK( 1 ) ) )
*
* COMPLEX work space for PCUNMTR
*
IF( WANTZ ) THEN
CALL PCUNMTR( 'L', UPLO, 'N', N, N, A, IA, JA, DESCA,
$ WORK( INDTAU ), Z, IZ, JZ, DESCZ,
$ WORK( INDWORK ), -1, IINFO )
SIZEPCUNMTR = INT( ABS( WORK( 1 ) ) )
ELSE
SIZEPCUNMTR = 0
END IF
*
* REAL work space for CSTEQR2
*
IF( WANTZ ) THEN
RSIZECSTEQR2 = MAX( 1, 2*N-2 )
ELSE
RSIZECSTEQR2 = 0
END IF
*
* Initialize the context of the single column distributed
* matrix required by CSTEQR2. This specific distribution
* allows each process to do 1/pth of the work updating matrix
* Q during CSTEQR2 and achieve some parallelization to an
* otherwise serial subroutine.
*
LDC = 0
IF( WANTZ ) THEN
CONTEXTC = SL_GRIDRESHAPE( DESCA( CTXT_ ), 0, 1, 1,
$ NPROCS, 1 )
CALL BLACS_GRIDINFO( CONTEXTC, NPROWC, NPCOLC, MYPROWC,
$ MYPCOLC )
NRC = NUMROC( N, NB_A, MYPROWC, 0, NPROCS )
LDC = MAX( 1, NRC )
CALL DESCINIT( DESCQR, N, N, NB, NB, 0, 0, CONTEXTC, LDC,
$ INFO )
END IF
*
* COMPLEX work space for CSTEQR2
*
IF( WANTZ ) THEN
SIZECSTEQR2 = N*LDC
ELSE
SIZECSTEQR2 = 0
END IF
*
* Set up pointers into the WORK array
*
INDTAU = 1
INDD = INDTAU + N
INDE = INDD + N
INDWORK = INDE + N
INDWORK2 = INDWORK + N*LDC
LLWORK = LWORK - INDWORK + 1
*
* Set up pointers into the RWORK array
*
INDRE = 1
INDRD = INDRE + N
INDRWORK = INDRD + N
LLRWORK = LRWORK - INDRWORK + 1
*
* Compute the total amount of space needed
*
LRWMIN = 2*N + RSIZECSTEQR2
LWMIN = 3*N + MAX( SIZEPCHETRD, SIZEPCUNMTR, SIZECSTEQR2 )
*
END IF
IF( INFO.EQ.0 ) THEN
IF( .NOT.( WANTZ .OR. LSAME( JOBZ, 'N' ) ) ) THEN
INFO = -1
ELSE IF( .NOT.( LOWER .OR. LSAME( UPLO, 'U' ) ) ) THEN
INFO = -2
ELSE IF( LWORK.LT.LWMIN .AND. LWORK.NE.-1 ) THEN
INFO = -14
ELSE IF( LRWORK.LT.LRWMIN .AND. LRWORK.NE.-1 ) THEN
INFO = -16
ELSE IF( IROFFA.NE.0 ) THEN
INFO = -5
ELSE IF( DESCA( MB_ ).NE.DESCA( NB_ ) ) THEN
INFO = -( 700+NB_ )
END IF
IF( WANTZ ) THEN
IF( IROFFA.NE.IROFFZ ) THEN
INFO = -10
ELSE IF( IAROW.NE.IZROW ) THEN
INFO = -10
ELSE IF( DESCA( M_ ).NE.DESCZ( M_ ) ) THEN
INFO = -( 1200+M_ )
ELSE IF( DESCA( N_ ).NE.DESCZ( N_ ) ) THEN
INFO = -( 1200+N_ )
ELSE IF( DESCA( MB_ ).NE.DESCZ( MB_ ) ) THEN
INFO = -( 1200+MB_ )
ELSE IF( DESCA( NB_ ).NE.DESCZ( NB_ ) ) THEN
INFO = -( 1200+NB_ )
ELSE IF( DESCA( RSRC_ ).NE.DESCZ( RSRC_ ) ) THEN
INFO = -( 1200+RSRC_ )
ELSE IF( DESCA( CTXT_ ).NE.DESCZ( CTXT_ ) ) THEN
INFO = -( 1200+CTXT_ )
END IF
END IF
END IF
IF( WANTZ ) THEN
IDUM1( 1 ) = ICHAR( 'V' )
ELSE
IDUM1( 1 ) = ICHAR( 'N' )
END IF
IDUM2( 1 ) = 1
IF( LOWER ) THEN
IDUM1( 2 ) = ICHAR( 'L' )
ELSE
IDUM1( 2 ) = ICHAR( 'U' )
END IF
IDUM2( 2 ) = 2
IF( LWORK.EQ.-1 ) THEN
IDUM1( 3 ) = -1
ELSE
IDUM1( 3 ) = 1
END IF
IDUM2( 3 ) = 3
IF( WANTZ ) THEN
CALL PCHK2MAT( N, 3, N, 3, IA, JA, DESCA, 7, N, 3, N, 3, IZ,
$ JZ, DESCZ, 12, 3, IDUM1, IDUM2, INFO )
ELSE
CALL PCHK1MAT( N, 3, N, 3, IA, JA, DESCA, 7, 3, IDUM1,
$ IDUM2, INFO )
END IF
WORK( 1 ) = CMPLX( LWMIN )
RWORK( 1 ) = REAL( LRWMIN )
END IF
*
IF( INFO.NE.0 ) THEN
CALL PXERBLA( DESCA( CTXT_ ), 'PCHEEV', -INFO )
IF( WANTZ )
$ CALL BLACS_GRIDEXIT( CONTEXTC )
RETURN
ELSE IF( LWORK.EQ.-1 .OR. LRWORK.EQ.-1 ) THEN
IF( WANTZ )
$ CALL BLACS_GRIDEXIT( CONTEXTC )
RETURN
END IF
*
* Scale matrix to allowable range, if necessary.
*
ISCALE = 0
*
ANRM = PCLANHE( 'M', UPLO, N, A, IA, JA, DESCA,
$ RWORK( INDRWORK ) )
*
*
IF( ANRM.GT.ZERO .AND. ANRM.LT.RMIN ) THEN
ISCALE = 1
SIGMA = RMIN / ANRM
ELSE IF( ANRM.GT.RMAX ) THEN
ISCALE = 1
SIGMA = RMAX / ANRM
END IF
*
IF( ISCALE.EQ.1 ) THEN
CALL PCLASCL( UPLO, ONE, SIGMA, N, N, A, IA, JA, DESCA, IINFO )
END IF
*
* Reduce Hermitian matrix to tridiagonal form.
*
CALL PCHETRD( UPLO, N, A, IA, JA, DESCA, RWORK( INDRD ),
$ RWORK( INDRE ), WORK( INDTAU ), WORK( INDWORK ),
$ LLWORK, IINFO )
*
* Copy the values of D, E to all processes.
*
DO 10 I = 1, N
CALL PCELGET( 'A', ' ', WORK( INDD+I-1 ), A, I+IA-1, I+JA-1,
$ DESCA )
RWORK( INDRD+I-1 ) = REAL( WORK( INDD+I-1 ) )
10 CONTINUE
IF( LSAME( UPLO, 'U' ) ) THEN
DO 20 I = 1, N - 1
CALL PCELGET( 'A', ' ', WORK( INDE+I-1 ), A, I+IA-1, I+JA,
$ DESCA )
RWORK( INDRE+I-1 ) = REAL( WORK( INDE+I-1 ) )
20 CONTINUE
ELSE
DO 30 I = 1, N - 1
CALL PCELGET( 'A', ' ', WORK( INDE+I-1 ), A, I+IA, I+JA-1,
$ DESCA )
RWORK( INDRE+I-1 ) = REAL( WORK( INDE+I-1 ) )
30 CONTINUE
END IF
*
IF( WANTZ ) THEN
*
CALL PCLASET( 'Full', N, N, CZERO, CONE, WORK( INDWORK ), 1, 1,
$ DESCQR )
*
* CSTEQR2 is a modified version of LAPACK's CSTEQR. The
* modifications allow each process to perform partial updates
* to matrix Q.
*
CALL CSTEQR2( 'I', N, RWORK( INDRD ), RWORK( INDRE ),
$ WORK( INDWORK ), LDC, NRC, RWORK( INDRWORK ),
$ INFO )
*
CALL PCGEMR2D( N, N, WORK( INDWORK ), 1, 1, DESCQR, Z, IA, JA,
$ DESCZ, CONTEXTC )
*
CALL PCUNMTR( 'L', UPLO, 'N', N, N, A, IA, JA, DESCA,
$ WORK( INDTAU ), Z, IZ, JZ, DESCZ,
$ WORK( INDWORK ), LLWORK, IINFO )
*
ELSE
*
CALL CSTEQR2( 'N', N, RWORK( INDRD ), RWORK( INDRE ),
$ WORK( INDWORK ), 1, 1, RWORK( INDRWORK ), INFO )
END IF
*
* Copy eigenvalues from workspace to output array
*
CALL SCOPY( N, RWORK( INDD ), 1, W, 1 )
*
* If matrix was scaled, then rescale eigenvalues appropriately.
*
IF( ISCALE.EQ.1 ) THEN
CALL SSCAL( N, ONE / SIGMA, W, 1 )
END IF
*
WORK( 1 ) = REAL( LWMIN )
*
* Free up resources
*
IF( WANTZ ) THEN
CALL BLACS_GRIDEXIT( CONTEXTC )
END IF
*
* Compare every ith eigenvalue, or all if there are only a few,
* across the process grid to check for heterogeneity.
*
IF( N.LE.ITHVAL ) THEN
J = N
K = 1
ELSE
J = N / ITHVAL
K = ITHVAL
END IF
*
LRMIN = INT( RWORK( 1 ) )
INDTAU = 0
INDE = INDTAU + J
DO 40 I = 1, J
RWORK( I+INDTAU ) = W( ( I-1 )*K+1 )
RWORK( I+INDE ) = W( ( I-1 )*K+1 )
40 CONTINUE
*
CALL SGAMN2D( DESCA( CTXT_ ), 'All', ' ', J, 1, RWORK( 1+INDTAU ),
$ J, 1, 1, -1, -1, 0 )
CALL SGAMX2D( DESCA( CTXT_ ), 'All', ' ', J, 1, RWORK( 1+INDE ),
$ J, 1, 1, -1, -1, 0 )
*
DO 50 I = 1, J
IF( INFO.EQ.0 .AND. ( RWORK( I+INDTAU )-RWORK( I+INDE ).NE.
$ ZERO ) ) THEN
INFO = N + 1
END IF
50 CONTINUE
RWORK( 1 ) = LRMIN
*
RETURN
*
* End of PCHEEV
*
END
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