SUBROUTINE PDSYNGST( IBTYPE, UPLO, N, A, IA, JA, DESCA, B, IB, JB,
$ DESCB, SCALE, WORK, LWORK, INFO )
*
* -- ScaLAPACK routine (version 1.7) --
* University of Tennessee, Knoxville, Oak Ridge National Laboratory,
* and University of California, Berkeley.
* October 15, 1999
*
* .. Scalar Arguments ..
CHARACTER UPLO
INTEGER IA, IB, IBTYPE, INFO, JA, JB, LWORK, N
DOUBLE PRECISION SCALE
* ..
* .. Array Arguments ..
INTEGER DESCA( * ), DESCB( * )
DOUBLE PRECISION A( * ), B( * ), WORK( * )
* ..
*
* Purpose
*
* =======
*
* PDSYNGST reduces a complex Hermitian-definite generalized
* eigenproblem to standard form.
*
* PDSYNGST performs the same function as PDHEGST, but is based on
* rank 2K updates, which are faster and more scalable than
* triangular solves (the basis of PDSYNGST).
*
* PDSYNGST calls PDHEGST when UPLO='U', hence PDHENGST provides
* improved performance only when UPLO='L', IBTYPE=1.
*
* PDSYNGST also calls PDHEGST when insufficient workspace is
* provided, hence PDSYNGST provides improved
* performance only when LWORK >= 2 * NP0 * NB + NQ0 * NB + NB * NB
*
* In the following sub( A ) denotes A( IA:IA+N-1, JA:JA+N-1 ) and
* sub( B ) denotes B( IB:IB+N-1, JB:JB+N-1 ).
*
* If IBTYPE = 1, the problem is sub( A )*x = lambda*sub( B )*x,
* and sub( A ) is overwritten by inv(U**H)*sub( A )*inv(U) or
* inv(L)*sub( A )*inv(L**H)
*
* If IBTYPE = 2 or 3, the problem is sub( A )*sub( B )*x = lambda*x or
* sub( B )*sub( A )*x = lambda*x, and sub( A ) is overwritten by
* U*sub( A )*U**H or L**H*sub( A )*L.
*
* sub( B ) must have been previously factorized as U**H*U or L*L**H by
* PDPOTRF.
*
* Notes
* =====
*
* Each global data object is described by an associated description
* vector. This vector stores the information required to establish
* the mapping between an object element and its corresponding process
* and memory location.
*
* Let A be a generic term for any 2D block cyclicly distributed array.
* Such a global array has an associated description vector DESCA.
* In the following comments, the character _ should be read as
* "of the global array".
*
* NOTATION STORED IN EXPLANATION
* --------------- -------------- --------------------------------------
* DTYPE_A(global) DESCA( DTYPE_ )The descriptor type. In this case,
* DTYPE_A = 1.
* 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 global
* array A.
* N_A (global) DESCA( N_ ) The number of columns in the global
* array A.
* MB_A (global) DESCA( MB_ ) The blocking factor used to distribute
* the rows of the array.
* NB_A (global) DESCA( NB_ ) The blocking factor used to distribute
* the columns of the array.
* RSRC_A (global) DESCA( RSRC_ ) The process row over which the first
* row of the array A is distributed.
* CSRC_A (global) DESCA( CSRC_ ) The process column over which the
* first column of the array A is
* distributed.
* LLD_A (local) DESCA( LLD_ ) The leading dimension of the local
* array. 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 ).
* An upper bound for these quantities may be computed by:
* LOCr( M ) <= ceil( ceil(M/MB_A)/NPROW )*MB_A
* LOCc( N ) <= ceil( ceil(N/NB_A)/NPCOL )*NB_A
*
* Arguments
* =========
*
* IBTYPE (global input) INTEGER
* = 1: compute inv(U**H)*sub( A )*inv(U) or
* inv(L)*sub( A )*inv(L**H);
* = 2 or 3: compute U*sub( A )*U**H or L**H*sub( A )*L.
*
* UPLO (global input) CHARACTER
* = 'U': Upper triangle of sub( A ) is stored and sub( B ) is
* factored as U**H*U;
* = 'L': Lower triangle of sub( A ) is stored and sub( B ) is
* factored as L*L**H.
*
* N (global input) INTEGER
* The order of the matrices sub( A ) and sub( B ). N >= 0.
*
* A (local input/local output) DOUBLE PRECISION pointer into the
* local memory to an array of dimension (LLD_A, LOCc(JA+N-1)).
* On entry, this array contains the local pieces of the
* N-by-N Hermitian distributed matrix sub( A ). If UPLO = 'U',
* the leading N-by-N upper triangular part of sub( A ) contains
* the upper triangular part of the matrix, and its strictly
* lower triangular part is not referenced. If UPLO = 'L', the
* leading N-by-N lower triangular part of sub( A ) contains
* the lower triangular part of the matrix, and its strictly
* upper triangular part is not referenced.
*
* On exit, if INFO = 0, the transformed matrix, stored in the
* same format as sub( A ).
*
* 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.
*
* B (local input) DOUBLE PRECISION pointer into the local memory
* to an array of dimension (LLD_B, LOCc(JB+N-1)). On entry,
* this array contains the local pieces of the triangular factor
* from the Cholesky factorization of sub( B ), as returned by
* PDPOTRF.
*
* IB (global input) INTEGER
* B's global row index, which points to the beginning of the
* submatrix which is to be operated on.
*
* JB (global input) INTEGER
* B's global column index, which points to the beginning of
* the submatrix which is to be operated on.
*
* DESCB (global and local input) INTEGER array of dimension DLEN_.
* The array descriptor for the distributed matrix B.
*
* SCALE (global output) DOUBLE PRECISION
* Amount by which the eigenvalues should be scaled to
* compensate for the scaling performed in this routine.
* At present, SCALE is always returned as 1.0, it is
* returned here to allow for future enhancement.
*
* WORK (local workspace/local output) DOUBLE PRECISION array,
* dimension (LWORK)
* On exit, WORK( 1 ) returns the minimal and optimal LWORK.
*
* LWORK (local or global input) INTEGER
* The dimension of the array WORK.
* LWORK is local input and must be at least
* LWORK >= MAX( NB * ( NP0 +1 ), 3 * NB )
*
* When IBTYPE = 1 and UPLO = 'L', PDSYNGST provides improved
* performance when LWORK >= 2 * NP0 * NB + NQ0 * NB + NB * NB
*
* where NB = MB_A = NB_A,
* NP0 = NUMROC( N, NB, 0, 0, NPROW ),
* NQ0 = NUMROC( N, NB, 0, 0, NPROW ),
*
* NUMROC ia a ScaLAPACK tool functions
* MYROW, MYCOL, NPROW and NPCOL can be determined by calling
* the subroutine BLACS_GRIDINFO.
*
* If LWORK = -1, then LWORK is global input and a workspace
* query is assumed; the routine only calculates the
* optimal size for all work arrays. Each of these
* values is returned in the first entry of the corresponding
* work array, 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.
*
* =====================================================================
*
*
*
* .. Parameters ..
DOUBLE PRECISION ONEHALF, ONE, MONE
PARAMETER ( ONEHALF = 0.5D0, ONE = 1.0D0, MONE = -1.0D0 )
INTEGER DLEN_, CTXT_, MB_, NB_, RSRC_, CSRC_, LLD_
PARAMETER ( DLEN_ = 9, CTXT_ = 2, MB_ = 5, NB_ = 6,
$ RSRC_ = 7, CSRC_ = 8, LLD_ = 9 )
* ..
* .. Local Scalars ..
LOGICAL LQUERY, UPPER
INTEGER I, IACOL, IAROW, IBCOL, IBROW, ICOFFA, ICOFFB,
$ ICTXT, INDAA, INDG, INDR, INDRT, IROFFA,
$ IROFFB, J, K, KB, LWMIN, LWOPT, MYCOL, MYROW,
$ NB, NP0, NPCOL, NPK, NPROW, NQ0, POSTK
* ..
* .. Local Arrays ..
INTEGER DESCAA( DLEN_ ), DESCG( DLEN_ ),
$ DESCR( DLEN_ ), DESCRT( DLEN_ ), IDUM1( 2 ),
$ IDUM2( 2 )
* ..
* .. External Functions ..
LOGICAL LSAME
INTEGER INDXG2P, NUMROC
EXTERNAL LSAME, INDXG2P, NUMROC
* ..
* .. External Subroutines ..
EXTERNAL BLACS_GRIDINFO, CHK1MAT, DESCSET, PCHK2MAT,
$ PDGEMM, PDLACPY, PDSYGST, PDSYMM, PDSYR2K,
$ PDTRSM, PXERBLA
* ..
* .. Intrinsic Functions ..
INTRINSIC DBLE, ICHAR, MAX, MIN, MOD
* ..
* .. Executable Statements ..
ICTXT = DESCA( CTXT_ )
CALL BLACS_GRIDINFO( ICTXT, NPROW, NPCOL, MYROW, MYCOL )
SCALE = 1.0D0
*
NB = DESCA( MB_ )
*
*
* Test the input parameters
*
INFO = 0
IF( NPROW.EQ.-1 ) THEN
INFO = -( 700+CTXT_ )
ELSE
UPPER = LSAME( UPLO, 'U' )
CALL CHK1MAT( N, 3, N, 3, IA, JA, DESCA, 7, INFO )
CALL CHK1MAT( N, 3, N, 3, IB, JB, DESCB, 11, INFO )
IF( INFO.EQ.0 ) THEN
IAROW = INDXG2P( IA, DESCA( MB_ ), MYROW, DESCA( RSRC_ ),
$ NPROW )
IBROW = INDXG2P( IB, DESCB( MB_ ), MYROW, DESCB( RSRC_ ),
$ NPROW )
IACOL = INDXG2P( JA, DESCA( NB_ ), MYCOL, DESCA( CSRC_ ),
$ NPCOL )
IBCOL = INDXG2P( JB, DESCB( NB_ ), MYCOL, DESCB( CSRC_ ),
$ NPCOL )
IROFFA = MOD( IA-1, DESCA( MB_ ) )
ICOFFA = MOD( JA-1, DESCA( NB_ ) )
IROFFB = MOD( IB-1, DESCB( MB_ ) )
ICOFFB = MOD( JB-1, DESCB( NB_ ) )
NP0 = NUMROC( N, NB, 0, 0, NPROW )
NQ0 = NUMROC( N, NB, 0, 0, NPCOL )
LWMIN = MAX( NB*( NP0+1 ), 3*NB )
IF( IBTYPE.EQ.1 .AND. .NOT.UPPER ) THEN
LWOPT = 2*NP0*NB + NQ0*NB + NB*NB
ELSE
LWOPT = LWMIN
END IF
WORK( 1 ) = DBLE( LWOPT )
LQUERY = ( LWORK.EQ.-1 )
IF( IBTYPE.LT.1 .OR. IBTYPE.GT.3 ) THEN
INFO = -1
ELSE IF( .NOT.UPPER .AND. .NOT.LSAME( UPLO, 'L' ) ) THEN
INFO = -2
ELSE IF( N.LT.0 ) THEN
INFO = -3
ELSE IF( IROFFA.NE.0 ) THEN
INFO = -5
ELSE IF( ICOFFA.NE.0 ) THEN
INFO = -6
ELSE IF( DESCA( MB_ ).NE.DESCA( NB_ ) ) THEN
INFO = -( 700+NB_ )
ELSE IF( IROFFB.NE.0 .OR. IBROW.NE.IAROW ) THEN
INFO = -9
ELSE IF( ICOFFB.NE.0 .OR. IBCOL.NE.IACOL ) THEN
INFO = -10
ELSE IF( DESCB( MB_ ).NE.DESCA( MB_ ) ) THEN
INFO = -( 1100+MB_ )
ELSE IF( DESCB( NB_ ).NE.DESCA( NB_ ) ) THEN
INFO = -( 1100+NB_ )
ELSE IF( ICTXT.NE.DESCB( CTXT_ ) ) THEN
INFO = -( 1100+CTXT_ )
ELSE IF( LWORK.LT.LWMIN .AND. .NOT.LQUERY ) THEN
INFO = -13
END IF
END IF
IDUM1( 1 ) = IBTYPE
IDUM2( 1 ) = 1
IF( UPPER ) THEN
IDUM1( 2 ) = ICHAR( 'U' )
ELSE
IDUM1( 2 ) = ICHAR( 'L' )
END IF
IDUM2( 2 ) = 2
CALL PCHK2MAT( N, 3, N, 3, IA, JA, DESCA, 7, N, 3, N, 3, IB,
$ JB, DESCB, 11, 2, IDUM1, IDUM2, INFO )
END IF
*
IF( INFO.NE.0 ) THEN
CALL PXERBLA( ICTXT, 'PDSYNGST', -INFO )
RETURN
ELSE IF( LQUERY ) THEN
RETURN
END IF
*
* Quick return if possible
*
IF( N.EQ.0 )
$ RETURN
*
*
IF( IBTYPE.NE.1 .OR. UPPER .OR. LWORK.LT.LWOPT ) THEN
CALL PDSYGST( IBTYPE, UPLO, N, A, IA, JA, DESCA, B, IB, JB,
$ DESCB, SCALE, INFO )
RETURN
END IF
*
CALL DESCSET( DESCG, N, NB, NB, NB, IAROW, IACOL, ICTXT, NP0 )
CALL DESCSET( DESCR, N, NB, NB, NB, IAROW, IACOL, ICTXT, NP0 )
CALL DESCSET( DESCRT, NB, N, NB, NB, IAROW, IACOL, ICTXT, NB )
CALL DESCSET( DESCAA, NB, NB, NB, NB, IAROW, IACOL, ICTXT, NB )
*
INDG = 1
INDR = INDG + DESCG( LLD_ )*NB
INDAA = INDR + DESCR( LLD_ )*NB
INDRT = INDAA + DESCAA( LLD_ )*NB
*
DO 30 K = 1, N, NB
*
KB = MIN( N-K+1, NB )
POSTK = K + KB
NPK = N - POSTK + 1
*
*
CALL PDLACPY( 'A', N-POSTK+1, KB, B, POSTK+IB-1, K+JB-1, DESCB,
$ WORK( INDG ), POSTK, 1, DESCG )
CALL PDLACPY( 'A', N-POSTK+1, KB, A, POSTK+IA-1, K+JA-1, DESCA,
$ WORK( INDR ), POSTK, 1, DESCR )
CALL PDLACPY( 'A', KB, K-1, A, K+IA-1, JA, DESCA,
$ WORK( INDRT ), 1, 1, DESCRT )
*
CALL PDLACPY( 'L', KB, KB, A, K+IA-1, K+JA-1, DESCA,
$ WORK( INDR ), K, 1, DESCR )
CALL PDTRSM( 'Right', 'L', 'N', 'N', NPK, KB, MONE, B, K+IB-1,
$ K+JB-1, DESCB, WORK( INDG ), POSTK, 1, DESCG )
*
CALL PDSYMM( 'Right', 'L', NPK, KB, ONEHALF, A, K+IA-1, K+JA-1,
$ DESCA, WORK( INDG ), POSTK, 1, DESCG, ONE,
$ WORK( INDR ), POSTK, 1, DESCR )
*
CALL PDSYR2K( 'Lower', 'No T', NPK, KB, ONE, WORK( INDG ),
$ POSTK, 1, DESCG, WORK( INDR ), POSTK, 1, DESCR,
$ ONE, A, POSTK+IA-1, POSTK+JA-1, DESCA )
*
CALL PDGEMM( 'No T', 'No Conj', NPK, K-1, KB, ONE,
$ WORK( INDG ), POSTK, 1, DESCG, WORK( INDRT ), 1,
$ 1, DESCRT, ONE, A, POSTK+IA-1, JA, DESCA )
*
CALL PDSYMM( 'Right', 'L', NPK, KB, ONE, WORK( INDR ), K, 1,
$ DESCR, WORK( INDG ), POSTK, 1, DESCG, ONE, A,
$ POSTK+IA-1, K+JA-1, DESCA )
*
CALL PDTRSM( 'Left', 'Lower', 'No Conj', 'Non-unit', KB, K-1,
$ ONE, B, K+IB-1, K+JB-1, DESCB, A, K+IA-1, JA,
$ DESCA )
*
CALL PDLACPY( 'L', KB, KB, A, K+IA-1, K+JA-1, DESCA,
$ WORK( INDAA ), 1, 1, DESCAA )
*
IF( MYROW.EQ.DESCAA( RSRC_ ) .AND. MYCOL.EQ.DESCAA( CSRC_ ) )
$ THEN
DO 20 I = 1, KB
DO 10 J = 1, I
WORK( INDAA+J-1+( I-1 )*DESCAA( LLD_ ) )
$ = WORK( INDAA+I-1+( J-1 )*DESCAA( LLD_ ) )
10 CONTINUE
20 CONTINUE
END IF
*
CALL PDTRSM( 'Left', 'Lower', 'No Conj', 'Non-unit', KB, KB,
$ ONE, B, K+IB-1, K+JB-1, DESCB, WORK( INDAA ), 1,
$ 1, DESCAA )
*
CALL PDTRSM( 'Right', 'Lower', 'Conj', 'Non-unit', KB, KB, ONE,
$ B, K+IB-1, K+JB-1, DESCB, WORK( INDAA ), 1, 1,
$ DESCAA )
*
CALL PDLACPY( 'L', KB, KB, WORK( INDAA ), 1, 1, DESCAA, A,
$ K+IA-1, K+JA-1, DESCA )
*
CALL PDTRSM( 'Right', 'Lower', 'Conj', 'Non-unit', NPK, KB,
$ ONE, B, K+IB-1, K+JB-1, DESCB, A, POSTK+IA-1,
$ K+JA-1, DESCA )
*
DESCR( CSRC_ ) = MOD( DESCR( CSRC_ )+1, NPCOL )
DESCG( CSRC_ ) = MOD( DESCG( CSRC_ )+1, NPCOL )
DESCRT( RSRC_ ) = MOD( DESCRT( RSRC_ )+1, NPROW )
DESCAA( RSRC_ ) = MOD( DESCAA( RSRC_ )+1, NPROW )
DESCAA( CSRC_ ) = MOD( DESCAA( CSRC_ )+1, NPCOL )
30 CONTINUE
*
WORK( 1 ) = DBLE( LWOPT )
*
RETURN
END