SUBROUTINE PCDTTRF( N, DL, D, DU, JA, DESCA, AF, LAF, WORK, LWORK, $ INFO ) * * * * -- ScaLAPACK routine (version 1.7) -- * University of Tennessee, Knoxville, Oak Ridge National Laboratory, * and University of California, Berkeley. * May 25, 2001 * * .. Scalar Arguments .. INTEGER INFO, JA, LAF, LWORK, N * .. * .. Array Arguments .. INTEGER DESCA( * ) COMPLEX AF( * ), D( * ), DL( * ), DU( * ), WORK( * ) * .. * * * Purpose * ======= * * PCDTTRF computes a LU factorization * of an N-by-N complex tridiagonal * diagonally dominant-like distributed matrix * A(1:N, JA:JA+N-1). * Reordering is used to increase parallelism in the factorization. * This reordering results in factors that are DIFFERENT from those * produced by equivalent sequential codes. These factors cannot * be used directly by users; however, they can be used in * subsequent calls to PCDTTRS to solve linear systems. * * The factorization has the form * * P A(1:N, JA:JA+N-1) P^T = L U * * where U is a tridiagonal upper triangular matrix and L is tridiagonal * lower triangular, and P is a permutation matrix. * * ===================================================================== * * Arguments * ========= * * * N (global input) INTEGER * The number of rows and columns to be operated on, i.e. the * order of the distributed submatrix A(1:N, JA:JA+N-1). N >= 0. * * DL (local input/local output) COMPLEX pointer to local * part of global vector storing the lower diagonal of the * matrix. Globally, DL(1) is not referenced, and DL must be * aligned with D. * Must be of size >= DESCA( NB_ ). * On exit, this array contains information containing the * factors of the matrix. * * D (local input/local output) COMPLEX pointer to local * part of global vector storing the main diagonal of the * matrix. * On exit, this array contains information containing the * factors of the matrix. * Must be of size >= DESCA( NB_ ). * * DU (local input/local output) COMPLEX pointer to local * part of global vector storing the upper diagonal of the * matrix. Globally, DU(n) is not referenced, and DU must be * aligned with D. * On exit, this array contains information containing the * factors of the matrix. * Must be of size >= DESCA( NB_ ). * * JA (global input) INTEGER * The index in the global array A that points to the start of * the matrix to be operated on (which may be either all of A * or a submatrix of A). * * DESCA (global and local input) INTEGER array of dimension DLEN. * if 1D type (DTYPE_A=501 or 502), DLEN >= 7; * if 2D type (DTYPE_A=1), DLEN >= 9. * The array descriptor for the distributed matrix A. * Contains information of mapping of A to memory. Please * see NOTES below for full description and options. * * AF (local output) COMPLEX array, dimension LAF. * Auxiliary Fillin Space. * Fillin is created during the factorization routine * PCDTTRF and this is stored in AF. If a linear system * is to be solved using PCDTTRS after the factorization * routine, AF *must not be altered* after the factorization. * * LAF (local input) INTEGER * Size of user-input Auxiliary Fillin space AF. Must be >= * 2*(NB+2) * If LAF is not large enough, an error code will be returned * and the minimum acceptable size will be returned in AF( 1 ) * * WORK (local workspace/local output) * COMPLEX temporary workspace. This space may * be overwritten in between calls to routines. WORK must be * the size given in LWORK. * On exit, WORK( 1 ) contains the minimal LWORK. * * LWORK (local input or global input) INTEGER * Size of user-input workspace WORK. * If LWORK is too small, the minimal acceptable size will be * returned in WORK(1) and an error code is returned. LWORK>= * 8*NPCOL * * INFO (local 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 = K<=NPROCS, the submatrix stored on processor * INFO and factored locally was not * diagonally dominant-like, and * the factorization was not completed. * If INFO = K>NPROCS, the submatrix stored on processor * INFO-NPROCS representing interactions with other * processors was not * stably factorable wo/interchanges, * and the factorization was not completed. * * ===================================================================== * * * Restrictions * ============ * * The following are restrictions on the input parameters. Some of these * are temporary and will be removed in future releases, while others * may reflect fundamental technical limitations. * * Non-cyclic restriction: VERY IMPORTANT! * P*NB>= mod(JA-1,NB)+N. * The mapping for matrices must be blocked, reflecting the nature * of the divide and conquer algorithm as a task-parallel algorithm. * This formula in words is: no processor may have more than one * chunk of the matrix. * * Blocksize cannot be too small: * If the matrix spans more than one processor, the following * restriction on NB, the size of each block on each processor, * must hold: * NB >= 2 * The bulk of parallel computation is done on the matrix of size * O(NB) on each processor. If this is too small, divide and conquer * is a poor choice of algorithm. * * Submatrix reference: * JA = IB * Alignment restriction that prevents unnecessary communication. * * * ===================================================================== * * * Notes * ===== * * If the factorization routine and the solve routine are to be called * separately (to solve various sets of righthand sides using the same * coefficient matrix), the auxiliary space AF *must not be altered* * between calls to the factorization routine and the solve routine. * * The best algorithm for solving banded and tridiagonal linear systems * depends on a variety of parameters, especially the bandwidth. * Currently, only algorithms designed for the case N/P >> bw are * implemented. These go by many names, including Divide and Conquer, * Partitioning, domain decomposition-type, etc. * For tridiagonal matrices, it is obvious: N/P >> bw(=1), and so D&C * algorithms are the appropriate choice. * * Algorithm description: Divide and Conquer * * The Divide and Conqer algorithm assumes the matrix is narrowly * banded compared with the number of equations. In this situation, * it is best to distribute the input matrix A one-dimensionally, * with columns atomic and rows divided amongst the processes. * The basic algorithm divides the tridiagonal matrix up into * P pieces with one stored on each processor, * and then proceeds in 2 phases for the factorization or 3 for the * solution of a linear system. * 1) Local Phase: * The individual pieces are factored independently and in * parallel. These factors are applied to the matrix creating * fillin, which is stored in a non-inspectable way in auxiliary * space AF. Mathematically, this is equivalent to reordering * the matrix A as P A P^T and then factoring the principal * leading submatrix of size equal to the sum of the sizes of * the matrices factored on each processor. The factors of * these submatrices overwrite the corresponding parts of A * in memory. * 2) Reduced System Phase: * A small ((P-1)) system is formed representing * interaction of the larger blocks, and is stored (as are its * factors) in the space AF. A parallel Block Cyclic Reduction * algorithm is used. For a linear system, a parallel front solve * followed by an analagous backsolve, both using the structure * of the factored matrix, are performed. * 3) Backsubsitution Phase: * For a linear system, a local backsubstitution is performed on * each processor in parallel. * * * Descriptors * =========== * * Descriptors now have *types* and differ from ScaLAPACK 1.0. * * Note: tridiagonal codes can use either the old two dimensional * or new one-dimensional descriptors, though the processor grid in * both cases *must be one-dimensional*. We describe both types below. * * 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 * * * One-dimensional descriptors: * * One-dimensional descriptors are a new addition to ScaLAPACK since * version 1.0. They simplify and shorten the descriptor for 1D * arrays. * * Since ScaLAPACK supports two-dimensional arrays as the fundamental * object, we allow 1D arrays to be distributed either over the * first dimension of the array (as if the grid were P-by-1) or the * 2nd dimension (as if the grid were 1-by-P). This choice is * indicated by the descriptor type (501 or 502) * as described below. * However, for tridiagonal matrices, since the objects being * distributed are the individual vectors storing the diagonals, we * have adopted the convention that both the P-by-1 descriptor and * the 1-by-P descriptor are allowed and are equivalent for * tridiagonal matrices. Thus, for tridiagonal matrices, * DTYPE_A = 501 or 502 can be used interchangeably * without any other change. * We require that the distributed vectors storing the diagonals of a * tridiagonal matrix be aligned with each other. Because of this, a * single descriptor, DESCA, serves to describe the distribution of * of all diagonals simultaneously. * * IMPORTANT NOTE: the actual BLACS grid represented by the * CTXT entry in the descriptor may be *either* P-by-1 or 1-by-P * irrespective of which one-dimensional descriptor type * (501 or 502) is input. * This routine will interpret the grid properly either way. * ScaLAPACK routines *do not support intercontext operations* so that * the grid passed to a single ScaLAPACK routine *must be the same* * for all array descriptors passed to that routine. * * NOTE: In all cases where 1D descriptors are used, 2D descriptors * may also be used, since a one-dimensional array is a special case * of a two-dimensional array with one dimension of size unity. * The two-dimensional array used in this case *must* be of the * proper orientation: * If the appropriate one-dimensional descriptor is DTYPEA=501 * (1 by P type), then the two dimensional descriptor must * have a CTXT value that refers to a 1 by P BLACS grid; * If the appropriate one-dimensional descriptor is DTYPEA=502 * (P by 1 type), then the two dimensional descriptor must * have a CTXT value that refers to a P by 1 BLACS grid. * * * Summary of allowed descriptors, types, and BLACS grids: * DTYPE 501 502 1 1 * BLACS grid 1xP or Px1 1xP or Px1 1xP Px1 * ----------------------------------------------------- * A OK OK OK NO * B NO OK NO OK * * Let A be a generic term for any 1D 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( 1 ) The descriptor type. For 1D grids, * TYPE_A = 501: 1-by-P grid. * TYPE_A = 502: P-by-1 grid. * CTXT_A (global) DESCA( 2 ) 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. * N_A (global) DESCA( 3 ) The size of the array dimension being * distributed. * NB_A (global) DESCA( 4 ) The blocking factor used to distribute * the distributed dimension of the array. * SRC_A (global) DESCA( 5 ) The process row or column over which the * first row or column of the array * is distributed. * Ignored DESCA( 6 ) Ignored for tridiagonal matrices. * Reserved DESCA( 7 ) Reserved for future use. * * * * ===================================================================== * * Code Developer: Andrew J. Cleary, University of Tennessee. * Current address: Lawrence Livermore National Labs. * This version released: August, 2001. * * ===================================================================== * * .. * .. Parameters .. REAL ONE, ZERO PARAMETER ( ONE = 1.0E+0 ) PARAMETER ( ZERO = 0.0E+0 ) COMPLEX CONE, CZERO PARAMETER ( CONE = ( 1.0E+0, 0.0E+0 ) ) PARAMETER ( CZERO = ( 0.0E+0, 0.0E+0 ) ) INTEGER INT_ONE PARAMETER ( INT_ONE = 1 ) INTEGER DESCMULT, BIGNUM PARAMETER (DESCMULT = 100, BIGNUM = DESCMULT * DESCMULT) INTEGER BLOCK_CYCLIC_2D, CSRC_, CTXT_, DLEN_, DTYPE_, $ LLD_, MB_, M_, NB_, N_, RSRC_ 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 ) * .. * .. Local Scalars .. INTEGER COMM_PROC, CSRC, FIRST_PROC, I, ICTXT, $ ICTXT_NEW, ICTXT_SAVE, IDUM3, JA_NEW, LAF_MIN, $ LEVEL_DIST, LLDA, MYCOL, MYROW, MY_NUM_COLS, $ NB, NP, NPCOL, NPROW, NP_SAVE, ODD_SIZE, $ PART_OFFSET, PART_SIZE, RETURN_CODE, STORE_N_A, $ TEMP, WORK_SIZE_MIN, WORK_U * .. * .. Local Arrays .. INTEGER DESCA_1XP( 7 ), PARAM_CHECK( 7, 3 ) * .. * .. External Subroutines .. EXTERNAL BLACS_GET, BLACS_GRIDEXIT, BLACS_GRIDINFO, $ CAXPY, CGEMM, CGERV2D, CGESD2D, CLACPY, $ CLATCPY, CPBTRF, CPOTRF, CSYRK, CTBTRS, CTRMM, $ CTRRV2D, CTRSD2D, CTRSM, CTRTRS, DESC_CONVERT, $ GLOBCHK, PXERBLA, RESHAPE * .. * .. External Functions .. LOGICAL LSAME INTEGER NUMROC COMPLEX CDOTC EXTERNAL CDOTC, LSAME, NUMROC * .. * .. Intrinsic Functions .. INTRINSIC ICHAR, MIN, MOD * .. * .. Executable Statements .. * * Test the input parameters * INFO = 0 * * Convert descriptor into standard form for easy access to * parameters, check that grid is of right shape. * DESCA_1XP( 1 ) = 501 * TEMP = DESCA( DTYPE_ ) IF( TEMP .EQ. 502 ) THEN * Temporarily set the descriptor type to 1xP type DESCA( DTYPE_ ) = 501 ENDIF * CALL DESC_CONVERT( DESCA, DESCA_1XP, RETURN_CODE ) * DESCA( DTYPE_ ) = TEMP * IF( RETURN_CODE .NE. 0) THEN INFO = -( 6*100 + 2 ) ENDIF * * Get values out of descriptor for use in code. * ICTXT = DESCA_1XP( 2 ) CSRC = DESCA_1XP( 5 ) NB = DESCA_1XP( 4 ) LLDA = DESCA_1XP( 6 ) STORE_N_A = DESCA_1XP( 3 ) * * Get grid parameters * * CALL BLACS_GRIDINFO( ICTXT, NPROW, NPCOL, MYROW, MYCOL ) NP = NPROW * NPCOL * * * IF( LWORK .LT. -1) THEN INFO = -10 ELSE IF ( LWORK .EQ. -1 ) THEN IDUM3 = -1 ELSE IDUM3 = 1 ENDIF * IF( N .LT. 0 ) THEN INFO = -1 ENDIF * IF( N+JA-1 .GT. STORE_N_A ) THEN INFO = -( 6*100 + 6 ) ENDIF * * Argument checking that is specific to Divide & Conquer routine * IF( NPROW .NE. 1 ) THEN INFO = -( 6*100+2 ) ENDIF * IF( N .GT. NP*NB-MOD( JA-1, NB )) THEN INFO = -( 1 ) CALL PXERBLA( ICTXT, $ 'PCDTTRF, D&C alg.: only 1 block per proc', $ -INFO ) RETURN ENDIF * IF((JA+N-1.GT.NB) .AND. ( NB.LT.2*INT_ONE )) THEN INFO = -( 6*100+4 ) CALL PXERBLA( ICTXT, $ 'PCDTTRF, D&C alg.: NB too small', $ -INFO ) RETURN ENDIF * * * Check auxiliary storage size * LAF_MIN = (12*NPCOL+3*NB) * IF( LAF .LT. LAF_MIN ) THEN INFO = -8 * put minimum value of laf into AF( 1 ) AF( 1 ) = LAF_MIN CALL PXERBLA( ICTXT, $ 'PCDTTRF: auxiliary storage error ', $ -INFO ) RETURN ENDIF * * Check worksize * WORK_SIZE_MIN = 8*NPCOL * WORK( 1 ) = WORK_SIZE_MIN * IF( LWORK .LT. WORK_SIZE_MIN ) THEN IF( LWORK .NE. -1 ) THEN INFO = -10 CALL PXERBLA( ICTXT, $ 'PCDTTRF: worksize error ', $ -INFO ) ENDIF RETURN ENDIF * * Pack params and positions into arrays for global consistency check * PARAM_CHECK( 7, 1 ) = DESCA(5) PARAM_CHECK( 6, 1 ) = DESCA(4) PARAM_CHECK( 5, 1 ) = DESCA(3) PARAM_CHECK( 4, 1 ) = DESCA(1) PARAM_CHECK( 3, 1 ) = JA PARAM_CHECK( 2, 1 ) = N PARAM_CHECK( 1, 1 ) = IDUM3 * PARAM_CHECK( 7, 2 ) = 605 PARAM_CHECK( 6, 2 ) = 604 PARAM_CHECK( 5, 2 ) = 603 PARAM_CHECK( 4, 2 ) = 601 PARAM_CHECK( 3, 2 ) = 5 PARAM_CHECK( 2, 2 ) = 1 PARAM_CHECK( 1, 2 ) = 10 * * Want to find errors with MIN( ), so if no error, set it to a big * number. If there already is an error, multiply by the the * descriptor multiplier. * IF( INFO.GE.0 ) THEN INFO = BIGNUM ELSE IF( INFO.LT.-DESCMULT ) THEN INFO = -INFO ELSE INFO = -INFO * DESCMULT END IF * * Check consistency across processors * CALL GLOBCHK( ICTXT, 7, PARAM_CHECK, 7, $ PARAM_CHECK( 1, 3 ), INFO ) * * Prepare output: set info = 0 if no error, and divide by DESCMULT * if error is not in a descriptor entry. * IF( INFO.EQ.BIGNUM ) THEN INFO = 0 ELSE IF( MOD( INFO, DESCMULT ) .EQ. 0 ) THEN INFO = -INFO / DESCMULT ELSE INFO = -INFO END IF * IF( INFO.LT.0 ) THEN CALL PXERBLA( ICTXT, 'PCDTTRF', -INFO ) RETURN END IF * * Quick return if possible * IF( N.EQ.0 ) $ RETURN * * * Adjust addressing into matrix space to properly get into * the beginning part of the relevant data * PART_OFFSET = NB*( (JA-1)/(NPCOL*NB) ) * IF ( (MYCOL-CSRC) .LT. (JA-PART_OFFSET-1)/NB ) THEN PART_OFFSET = PART_OFFSET + NB ENDIF * IF ( MYCOL .LT. CSRC ) THEN PART_OFFSET = PART_OFFSET - NB ENDIF * * Form a new BLACS grid (the "standard form" grid) with only procs * holding part of the matrix, of size 1xNP where NP is adjusted, * starting at csrc=0, with JA modified to reflect dropped procs. * * First processor to hold part of the matrix: * FIRST_PROC = MOD( ( JA-1 )/NB+CSRC, NPCOL ) * * Calculate new JA one while dropping off unused processors. * JA_NEW = MOD( JA-1, NB ) + 1 * * Save and compute new value of NP * NP_SAVE = NP NP = ( JA_NEW+N-2 )/NB + 1 * * Call utility routine that forms "standard-form" grid * CALL RESHAPE( ICTXT, INT_ONE, ICTXT_NEW, INT_ONE, $ FIRST_PROC, INT_ONE, NP ) * * Use new context from standard grid as context. * ICTXT_SAVE = ICTXT ICTXT = ICTXT_NEW DESCA_1XP( 2 ) = ICTXT_NEW * * Get information about new grid. * CALL BLACS_GRIDINFO( ICTXT, NPROW, NPCOL, MYROW, MYCOL ) * * Drop out processors that do not have part of the matrix. * IF( MYROW .LT. 0 ) THEN GOTO 1234 ENDIF * * ******************************** * Values reused throughout routine * * User-input value of partition size * PART_SIZE = NB * * Number of columns in each processor * MY_NUM_COLS = NUMROC( N, PART_SIZE, MYCOL, 0, NPCOL ) * * Offset in columns to beginning of main partition in each proc * IF ( MYCOL .EQ. 0 ) THEN PART_OFFSET = PART_OFFSET+MOD( JA_NEW-1, PART_SIZE ) MY_NUM_COLS = MY_NUM_COLS - MOD(JA_NEW-1, PART_SIZE ) ENDIF * * Size of main (or odd) partition in each processor * ODD_SIZE = MY_NUM_COLS IF ( MYCOL .LT. NP-1 ) THEN ODD_SIZE = ODD_SIZE - INT_ONE ENDIF * * Offset to workspace for Upper triangular factor * WORK_U = INT_ONE*ODD_SIZE + 3 * * * Zero out space for fillin * DO 10 I=1, LAF_MIN AF( I ) = CZERO 10 CONTINUE * * Begin main code * * ******************************************************************** * PHASE 1: Local computation phase. ******************************************************************** * * IF ( MYCOL .LT. NP-1 ) THEN * Transfer last triangle D_i of local matrix to next processor * which needs it to calculate fillin due to factorization of * its main (odd) block A_i. * Overlap the send with the factorization of A_i. * CALL CTRSD2D( ICTXT, 'U', 'N', 1, 1, $ DU( PART_OFFSET+ODD_SIZE+1 ), LLDA-1, 0, $ MYCOL+1 ) * ENDIF * * * Factor main partition A_i = L_i {U_i} in each processor * CALL CDTTRF( ODD_SIZE, DL( PART_OFFSET+2 ), D( PART_OFFSET+1 ), $ DU( PART_OFFSET+1 ), INFO ) * IF( INFO.NE.0 ) THEN INFO = MYCOL+1 GOTO 1500 ENDIF * * IF ( MYCOL .LT. NP-1 ) THEN * * Apply factorization to lower connection block BL_i * Apply factorization to upper connection block BU_i * * * Perform the triangular solve {U_i}^C{BL'}_i^C = {BL_i}^C * * DL( PART_OFFSET+ODD_SIZE+1 ) = $ ( DL( PART_OFFSET+ODD_SIZE+1 ) ) $ / ( D( PART_OFFSET+ODD_SIZE ) ) * * * Compute contribution to diagonal block(s) of reduced system. * {C'}_i = {C_i}-{{BL'}_i}{{BU'}_i} * * D( PART_OFFSET+ODD_SIZE+1 ) = D( PART_OFFSET+ODD_SIZE+1 )- $ DL( PART_OFFSET+ODD_SIZE+1 )*DU( PART_OFFSET+ODD_SIZE ) * ENDIF * End of "if ( MYCOL .lt. NP-1 )..." loop * * 1500 CONTINUE * If the processor could not locally factor, it jumps here. * IF ( MYCOL .NE. 0 ) THEN * * Move entry that causes spike to auxiliary storage * AF( WORK_U+1 ) = ( DL( PART_OFFSET+1 ) ) * IF (INFO.EQ.0) THEN * * Calculate the "spike" fillin, ${L_i} {{GU}_i} = {DL_i}$ . * CALL CDTTRSV( 'L', 'N', ODD_SIZE, INT_ONE, $ DL( PART_OFFSET+2 ), D( PART_OFFSET+1 ), $ DU( PART_OFFSET+1 ), AF( WORK_U+1 ), ODD_SIZE, $ INFO ) * * * Calculate the "spike" fillin, ${U_i}^C {{GL}_i}^C = {DU_i}^C$ * CALL CTRRV2D( ICTXT, 'U', 'N', 1, 1, AF( 1 ), ODD_SIZE, 0, $ MYCOL-1 ) * AF( 1 ) = CONJG( AF( 1 ) ) * CALL CDTTRSV( 'U', 'C', ODD_SIZE, INT_ONE, $ DL( PART_OFFSET+2 ), D( PART_OFFSET+1 ), $ DU( PART_OFFSET+1 ), $ AF( 1 ), ODD_SIZE, INFO ) * * * Calculate the update block for previous proc, E_i = GL_i{GU_i} * AF( ODD_SIZE+3 ) = -CONE * $ CDOTC( ODD_SIZE, AF( 1 ), 1, AF( WORK_U+1 ), 1 ) * * * Initiate send of E_i to previous processor to overlap * with next computation. * CALL CGESD2D( ICTXT, INT_ONE, INT_ONE, AF( ODD_SIZE+3 ), $ INT_ONE, 0, MYCOL-1 ) * * IF ( MYCOL .LT. NP-1 ) THEN * * Calculate off-diagonal block(s) of reduced system. * Note: for ease of use in solution of reduced system, store * L's off-diagonal block in conjugate transpose form. * AF( ODD_SIZE+1 ) = -CONE $ * CONJG( DL( PART_OFFSET+ODD_SIZE+1 ) $ * AF( WORK_U+ODD_SIZE ) ) * * AF(WORK_U+(ODD_SIZE)+1 ) = -CONE $ * DU( PART_OFFSET+ODD_SIZE ) $ * CONJG( AF( ODD_SIZE ) ) * ENDIF * ENDIF * End of "if ( MYCOL .ne. 0 )..." * ENDIF * End of "if (info.eq.0) then" * * * Check to make sure no processors have found errors * CALL IGAMX2D( ICTXT, 'A', ' ', 1, 1, INFO, 1, INFO, INFO, $ -1, 0, 0 ) * IF( MYCOL.EQ.0 ) THEN CALL IGEBS2D( ICTXT, 'A', ' ', 1, 1, INFO, 1 ) ELSE CALL IGEBR2D( ICTXT, 'A', ' ', 1, 1, INFO, 1, 0, 0 ) ENDIF * IF ( INFO.NE.0 ) THEN GOTO 1000 ENDIF * No errors found, continue * * ******************************************************************** * PHASE 2: Formation and factorization of Reduced System. ******************************************************************** * * Gather up local sections of reduced system * * * The last processor does not participate in the factorization of * the reduced system, having sent its E_i already. IF( MYCOL .EQ. NPCOL-1 ) THEN GOTO 14 ENDIF * * Initiate send of off-diag block(s) to overlap with next part. * Off-diagonal block needed on neighboring processor to start * algorithm. * IF( (MOD( MYCOL+1, 2 ) .EQ. 0) .AND. ( MYCOL .GT. 0 ) ) THEN * CALL CGESD2D( ICTXT, INT_ONE, INT_ONE, $ AF( ODD_SIZE+1 ), $ INT_ONE, 0, MYCOL-1 ) * CALL CGESD2D( ICTXT, INT_ONE, INT_ONE, $ AF( WORK_U+ODD_SIZE+1 ), $ INT_ONE, 0, MYCOL-1 ) * ENDIF * * Copy last diagonal block into AF storage for subsequent * operations. * AF( ODD_SIZE+2 ) = $ CMPLX( D( PART_OFFSET+ODD_SIZE+1 ) ) * * Receive cont. to diagonal block that is stored on this proc. * IF( MYCOL.LT. NPCOL-1 ) THEN * CALL CGERV2D( ICTXT, INT_ONE, INT_ONE, $ AF( ODD_SIZE+2+1 ), $ INT_ONE, 0, $ MYCOL+1 ) * * Add contribution to diagonal block * AF( ODD_SIZE+2 ) = AF( ODD_SIZE+2 )+AF( ODD_SIZE+3 ) * ENDIF * * * ************************************* * Modification Loop * * The distance for sending and receiving for each level starts * at 1 for the first level. LEVEL_DIST = 1 * * Do until this proc is needed to modify other procs' equations * 12 CONTINUE IF( MOD( (MYCOL+1)/LEVEL_DIST, 2) .NE. 0 ) GOTO 11 * * Receive and add contribution to diagonal block from the left * IF( MYCOL-LEVEL_DIST .GE. 0 ) THEN CALL CGERV2D( ICTXT, INT_ONE, INT_ONE, WORK( 1 ), $ INT_ONE, 0, MYCOL-LEVEL_DIST ) * AF( ODD_SIZE+2 ) = AF( ODD_SIZE+2 )+WORK( 1 ) * ENDIF * * Receive and add contribution to diagonal block from the right * IF( MYCOL+LEVEL_DIST .LT. NPCOL-1 ) THEN CALL CGERV2D( ICTXT, INT_ONE, INT_ONE, WORK( 1 ), $ INT_ONE, 0, MYCOL+LEVEL_DIST ) * AF( ODD_SIZE+2 ) = AF( ODD_SIZE+2 )+WORK( 1 ) * ENDIF * LEVEL_DIST = LEVEL_DIST*2 * GOTO 12 11 CONTINUE * [End of GOTO Loop] * * * ********************************* * Calculate and use this proc's blocks to modify other procs'... IF( AF( ODD_SIZE+2 ) .EQ. CZERO ) THEN INFO = NPCOL + MYCOL ENDIF * * **************************************************************** * Receive offdiagonal block from processor to right. * If this is the first group of processors, the receive comes * from a different processor than otherwise. * IF( LEVEL_DIST .EQ. 1 )THEN COMM_PROC = MYCOL + 1 * * Move block into place that it will be expected to be for * calcs. * AF( WORK_U+ODD_SIZE+3 ) = AF( ODD_SIZE+1 ) * AF( ODD_SIZE+3 ) = AF( WORK_U+ODD_SIZE+1 ) * ELSE COMM_PROC = MYCOL + LEVEL_DIST/2 ENDIF * IF( MYCOL/LEVEL_DIST .LE. (NPCOL-1)/LEVEL_DIST-2 )THEN * CALL CGERV2D( ICTXT, INT_ONE, INT_ONE, $ AF( ODD_SIZE+1 ), $ INT_ONE, 0, COMM_PROC ) * CALL CGERV2D( ICTXT, INT_ONE, INT_ONE, $ AF( WORK_U+ODD_SIZE+1 ), $ INT_ONE, 0, COMM_PROC ) * IF( INFO .EQ. 0 ) THEN * * * Modify lower off_diagonal block with diagonal block * * AF( ODD_SIZE+1 ) = AF( ODD_SIZE+1 ) $ / CONJG( AF( ODD_SIZE+2 ) ) * ENDIF * End of "if ( info.eq.0 ) then" * * Calculate contribution from this block to next diagonal block * WORK( 1 ) = -ONE*CONJG( AF( ODD_SIZE+1 ) )* $ AF( WORK_U+(ODD_SIZE)+1 ) * * Send contribution to diagonal block's owning processor. * CALL CGESD2D( ICTXT, INT_ONE, INT_ONE, WORK( 1 ), INT_ONE, $ 0, MYCOL+LEVEL_DIST ) * ENDIF * End of "if( mycol/level_dist .le. (npcol-1)/level_dist-2 )..." * * * **************************************************************** * Receive off_diagonal block from left and use to finish with this * processor. * IF( (MYCOL/LEVEL_DIST .GT. 0 ).AND. $ ( MYCOL/LEVEL_DIST .LE. (NPCOL-1)/LEVEL_DIST-1 ) ) THEN * IF( LEVEL_DIST .GT. 1)THEN * * Receive offdiagonal block(s) from proc level_dist/2 to the * left * CALL CGERV2D( ICTXT, INT_ONE, INT_ONE, $ AF( WORK_U+ODD_SIZE+2+1 ), $ INT_ONE, 0, MYCOL-LEVEL_DIST/2 ) * * Receive offdiagonal block(s) from proc level_dist/2 to the * left * CALL CGERV2D( ICTXT, INT_ONE, INT_ONE, $ AF( ODD_SIZE+2+1 ), $ INT_ONE, 0, MYCOL-LEVEL_DIST/2 ) * ENDIF * * IF( INFO.EQ.0 ) THEN * * Use diagonal block(s) to modify this offdiagonal block * AF( ODD_SIZE+3 ) = AF( ODD_SIZE+3 ) $ / ( AF( ODD_SIZE+2 ) ) * * ENDIF * End of "if( info.eq.0 ) then" * * Use offdiag block(s) to calculate modification to diag block * of processor to the left * WORK( 1 ) = -ONE*AF( ODD_SIZE+3 ) $ *CONJG( AF( WORK_U+ODD_SIZE+3 ) ) * * Send contribution to diagonal block's owning processor. * CALL CGESD2D( ICTXT, INT_ONE, INT_ONE, WORK( 1 ), INT_ONE, $ 0, MYCOL-LEVEL_DIST ) * * ******************************************************* * IF( MYCOL/LEVEL_DIST .LE. (NPCOL-1)/LEVEL_DIST-2 ) THEN * * Decide which processor offdiagonal block(s) goes to * IF( ( MOD( MYCOL/( 2*LEVEL_DIST ),2 )) .EQ.0 ) THEN COMM_PROC = MYCOL + LEVEL_DIST ELSE COMM_PROC = MYCOL - LEVEL_DIST ENDIF * * Use offdiagonal blocks to calculate offdiag * block to send to neighboring processor. Depending * on circumstances, may need to transpose the matrix. * WORK( 1 ) = -ONE*AF( WORK_U+ODD_SIZE+3 ) $ * AF( ODD_SIZE+1 ) * * Send contribution to offdiagonal block's owning processor. * CALL CGESD2D( ICTXT, INT_ONE, INT_ONE, WORK( 1 ), INT_ONE, $ 0, COMM_PROC ) * WORK( 1 ) = -ONE*AF( ODD_SIZE+3 ) $ * AF( WORK_U+ODD_SIZE+1 ) * * Send contribution to offdiagonal block's owning processor. * CALL CGESD2D( ICTXT, INT_ONE, INT_ONE, WORK( 1 ), INT_ONE, $ 0, COMM_PROC ) * ENDIF * ENDIF * End of "if( mycol/level_dist.le. (npcol-1)/level_dist -1 )..." * 14 CONTINUE * * 1000 CONTINUE * * * Free BLACS space used to hold standard-form grid. * IF( ICTXT_SAVE .NE. ICTXT_NEW ) THEN CALL BLACS_GRIDEXIT( ICTXT_NEW ) ENDIF * 1234 CONTINUE * * Restore saved input parameters * ICTXT = ICTXT_SAVE NP = NP_SAVE * * Output minimum worksize * WORK( 1 ) = WORK_SIZE_MIN * * Make INFO consistent across processors * CALL IGAMX2D( ICTXT, 'A', ' ', 1, 1, INFO, 1, INFO, INFO, $ -1, 0, 0 ) * IF( MYCOL.EQ.0 ) THEN CALL IGEBS2D( ICTXT, 'A', ' ', 1, 1, INFO, 1 ) ELSE CALL IGEBR2D( ICTXT, 'A', ' ', 1, 1, INFO, 1, 0, 0 ) ENDIF * * RETURN * * End of PCDTTRF * END

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