/*! \file
Copyright (c) 2003, The Regents of the University of California, through
Lawrence Berkeley National Laboratory (subject to receipt of any required 
approvals from U.S. Dept. of Energy) 

All rights reserved. 

The source code is distributed under BSD license, see the file License.txt
at the top-level directory.
*/

/*! @file sgssv.c
 * \brief Solves the system of linear equations A*X=B 
 *
 * <pre>
 * -- SuperLU routine (version 3.0) --
 * Univ. of California Berkeley, Xerox Palo Alto Research Center,
 * and Lawrence Berkeley National Lab.
 * October 15, 2003
 * </pre>  
 */
#include "slu_sdefs.h"

/*! \brief
 *
 * <pre>
 * Purpose
 * =======
 *
 * SGSSV solves the system of linear equations A*X=B, using the
 * LU factorization from SGSTRF. It performs the following steps:
 *
 *   1. If A is stored column-wise (A->Stype = SLU_NC):
 *
 *      1.1. Permute the columns of A, forming A*Pc, where Pc
 *           is a permutation matrix. For more details of this step, 
 *           see sp_preorder.c.
 *
 *      1.2. Factor A as Pr*A*Pc=L*U with the permutation Pr determined
 *           by Gaussian elimination with partial pivoting.
 *           L is unit lower triangular with offdiagonal entries
 *           bounded by 1 in magnitude, and U is upper triangular.
 *
 *      1.3. Solve the system of equations A*X=B using the factored
 *           form of A.
 *
 *   2. If A is stored row-wise (A->Stype = SLU_NR), apply the
 *      above algorithm to the transpose of A:
 *
 *      2.1. Permute columns of transpose(A) (rows of A),
 *           forming transpose(A)*Pc, where Pc is a permutation matrix. 
 *           For more details of this step, see sp_preorder.c.
 *
 *      2.2. Factor A as Pr*transpose(A)*Pc=L*U with the permutation Pr
 *           determined by Gaussian elimination with partial pivoting.
 *           L is unit lower triangular with offdiagonal entries
 *           bounded by 1 in magnitude, and U is upper triangular.
 *
 *      2.3. Solve the system of equations A*X=B using the factored
 *           form of A.
 *
 *   See supermatrix.h for the definition of 'SuperMatrix' structure.
 * 
 * Arguments
 * =========
 *
 * options (input) superlu_options_t*
 *         The structure defines the input parameters to control
 *         how the LU decomposition will be performed and how the
 *         system will be solved.
 *
 * A       (input) SuperMatrix*
 *         Matrix A in A*X=B, of dimension (A->nrow, A->ncol). The number
 *         of linear equations is A->nrow. Currently, the type of A can be:
 *         Stype = SLU_NC or SLU_NR; Dtype = SLU_S; Mtype = SLU_GE.
 *         In the future, more general A may be handled.
 *
 * perm_c  (input/output) int*
 *         If A->Stype = SLU_NC, column permutation vector of size A->ncol
 *         which defines the permutation matrix Pc; perm_c[i] = j means 
 *         column i of A is in position j in A*Pc.
 *         If A->Stype = SLU_NR, column permutation vector of size A->nrow
 *         which describes permutation of columns of transpose(A) 
 *         (rows of A) as described above.
 * 
 *         If options->ColPerm = MY_PERMC or options->Fact = SamePattern or
 *            options->Fact = SamePattern_SameRowPerm, it is an input argument.
 *            On exit, perm_c may be overwritten by the product of the input
 *            perm_c and a permutation that postorders the elimination tree
 *            of Pc'*A'*A*Pc; perm_c is not changed if the elimination tree
 *            is already in postorder.
 *         Otherwise, it is an output argument.
 * 
 * perm_r  (input/output) int*
 *         If A->Stype = SLU_NC, row permutation vector of size A->nrow, 
 *         which defines the permutation matrix Pr, and is determined 
 *         by partial pivoting.  perm_r[i] = j means row i of A is in 
 *         position j in Pr*A.
 *         If A->Stype = SLU_NR, permutation vector of size A->ncol, which
 *         determines permutation of rows of transpose(A)
 *         (columns of A) as described above.
 *
 *         If options->RowPerm = MY_PERMR or
 *            options->Fact = SamePattern_SameRowPerm, perm_r is an
 *            input argument.
 *         otherwise it is an output argument.
 *
 * L       (output) SuperMatrix*
 *         The factor L from the factorization 
 *             Pr*A*Pc=L*U              (if A->Stype = SLU_NC) or
 *             Pr*transpose(A)*Pc=L*U   (if A->Stype = SLU_NR).
 *         Uses compressed row subscripts storage for supernodes, i.e.,
 *         L has types: Stype = SLU_SC, Dtype = SLU_S, Mtype = SLU_TRLU.
 *         
 * U       (output) SuperMatrix*
 *	   The factor U from the factorization 
 *             Pr*A*Pc=L*U              (if A->Stype = SLU_NC) or
 *             Pr*transpose(A)*Pc=L*U   (if A->Stype = SLU_NR).
 *         Uses column-wise storage scheme, i.e., U has types:
 *         Stype = SLU_NC, Dtype = SLU_S, Mtype = SLU_TRU.
 *
 * B       (input/output) SuperMatrix*
 *         B has types: Stype = SLU_DN, Dtype = SLU_S, Mtype = SLU_GE.
 *         On entry, the right hand side matrix.
 *         On exit, the solution matrix if info = 0;
 *
 * stat   (output) SuperLUStat_t*
 *        Record the statistics on runtime and floating-point operation count.
 *        See util.h for the definition of 'SuperLUStat_t'.
 *
 * info    (output) int*
 *	   = 0: successful exit
 *         > 0: if info = i, and i is
 *             <= A->ncol: U(i,i) is exactly zero. The factorization has
 *                been completed, but the factor U is exactly singular,
 *                so the solution could not be computed.
 *             > A->ncol: number of bytes allocated when memory allocation
 *                failure occurred, plus A->ncol.
 * </pre>
 */

void
sgssv(superlu_options_t *options, SuperMatrix *A, int *perm_c, int *perm_r,
      SuperMatrix *L, SuperMatrix *U, SuperMatrix *B,
      SuperLUStat_t *stat, int *info )
{

    DNformat *Bstore;
    SuperMatrix *AA;/* A in SLU_NC format used by the factorization routine.*/
    SuperMatrix AC; /* Matrix postmultiplied by Pc */
    int      lwork = 0, *etree, i;
    GlobalLU_t Glu; /* Not needed on return. */
    
    /* Set default values for some parameters */
    int      panel_size;     /* panel size */
    int      relax;          /* no of columns in a relaxed snodes */
    int      permc_spec;
    trans_t  trans = NOTRANS;
    double   *utime;
    double   t;	/* Temporary time */

    /* Test the input parameters ... */
    *info = 0;
    Bstore = B->Store;
    if ( options->Fact != DOFACT ) *info = -1;
    else if ( A->nrow != A->ncol || A->nrow < 0 ||
	 (A->Stype != SLU_NC && A->Stype != SLU_NR) ||
	 A->Dtype != SLU_S || A->Mtype != SLU_GE )
	*info = -2;
    else if ( B->ncol < 0 || Bstore->lda < SUPERLU_MAX(0, A->nrow) ||
	B->Stype != SLU_DN || B->Dtype != SLU_S || B->Mtype != SLU_GE )
	*info = -7;
    if ( *info != 0 ) {
	i = -(*info);
	input_error("sgssv", &i);
	return;
    }

    utime = stat->utime;

    /* Convert A to SLU_NC format when necessary. */
    if ( A->Stype == SLU_NR ) {
	NRformat *Astore = A->Store;
	AA = (SuperMatrix *) SUPERLU_MALLOC( sizeof(SuperMatrix) );
	sCreate_CompCol_Matrix(AA, A->ncol, A->nrow, Astore->nnz, 
			       Astore->nzval, Astore->colind, Astore->rowptr,
			       SLU_NC, A->Dtype, A->Mtype);
	trans = TRANS;
    } else {
        if ( A->Stype == SLU_NC ) AA = A;
    }

    t = SuperLU_timer_();
    /*
     * Get column permutation vector perm_c[], according to permc_spec:
     *   permc_spec = NATURAL:  natural ordering 
     *   permc_spec = MMD_AT_PLUS_A: minimum degree on structure of A'+A
     *   permc_spec = MMD_ATA:  minimum degree on structure of A'*A
     *   permc_spec = COLAMD:   approximate minimum degree column ordering
     *   permc_spec = MY_PERMC: the ordering already supplied in perm_c[]
     */
    permc_spec = options->ColPerm;
    if ( permc_spec != MY_PERMC && options->Fact == DOFACT )
      get_perm_c(permc_spec, AA, perm_c);
    utime[COLPERM] = SuperLU_timer_() - t;

    etree = intMalloc(A->ncol);

    t = SuperLU_timer_();
    sp_preorder(options, AA, perm_c, etree, &AC);
    utime[ETREE] = SuperLU_timer_() - t;

    panel_size = sp_ienv(1);
    relax = sp_ienv(2);

    /*printf("Factor PA = LU ... relax %d\tw %d\tmaxsuper %d\trowblk %d\n", 
	  relax, panel_size, sp_ienv(3), sp_ienv(4));*/
    t = SuperLU_timer_(); 
    /* Compute the LU factorization of A. */
    sgstrf(options, &AC, relax, panel_size, etree,
            NULL, lwork, perm_c, perm_r, L, U, &Glu, stat, info);
    utime[FACT] = SuperLU_timer_() - t;

    t = SuperLU_timer_();
    if ( *info == 0 ) {
        /* Solve the system A*X=B, overwriting B with X. */
        sgstrs (trans, L, U, perm_c, perm_r, B, stat, info);
    }
    utime[SOLVE] = SuperLU_timer_() - t;

    SUPERLU_FREE (etree);
    Destroy_CompCol_Permuted(&AC);
    if ( A->Stype == SLU_NR ) {
	Destroy_SuperMatrix_Store(AA);
	SUPERLU_FREE(AA);
    }

}
