/*! \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 dcolumn_bmod.c
 *  \brief performs numeric block updates
 *
 * <pre>
 * -- SuperLU routine (version 3.0) --
 * Univ. of California Berkeley, Xerox Palo Alto Research Center,
 * and Lawrence Berkeley National Lab.
 * October 15, 2003
 *
 * Copyright (c) 1994 by Xerox Corporation.  All rights reserved.
 *
 * THIS MATERIAL IS PROVIDED AS IS, WITH ABSOLUTELY NO WARRANTY
 * EXPRESSED OR IMPLIED.  ANY USE IS AT YOUR OWN RISK.
 *
 *  Permission is hereby granted to use or copy this program for any
 *  purpose, provided the above notices are retained on all copies.
 *  Permission to modify the code and to distribute modified code is
 *  granted, provided the above notices are retained, and a notice that
 *  the code was modified is included with the above copyright notice.
 * </pre>
 */

#include <stdio.h>
#include <stdlib.h>
#include "slu_ddefs.h"

/*! \brief
 *
 * <pre>
 * Purpose:
 * ========
 * Performs numeric block updates (sup-col) in topological order.
 * It features: col-col, 2cols-col, 3cols-col, and sup-col updates.
 * Special processing on the supernodal portion of L\\U[*,j]
 * Return value:   0 - successful return
 *               > 0 - number of bytes allocated when run out of space
 * </pre>
 */
int dcolumn_bmod(
    const int jcol,     /* in */
    const int nseg,     /* in */
    double* dense,      /* in */
    double* tempv,      /* working array */
    int* segrep,        /* in */
    int* repfnz,        /* in */
    int fpanelc,        /* in -- first column in the current panel */
    GlobalLU_t* Glu,    /* modified */
    SuperLUStat_t* stat /* output */
) {
#ifdef _CRAY
    _fcd ftcs1 = _cptofcd("L", strlen("L")),
         ftcs2 = _cptofcd("N", strlen("N")),
         ftcs3 = _cptofcd("U", strlen("U"));
#endif
    int incx = 1, incy = 1;
    double alpha, beta;

    /* krep = representative of current k-th supernode
     * fsupc = first supernodal column
     * nsupc = no of columns in supernode
     * nsupr = no of rows in supernode (used as leading dimension)
     * luptr = location of supernodal LU-block in storage
     * kfnz = first nonz in the k-th supernodal segment
     * no_zeros = no of leading zeros in a supernodal U-segment
     */
    double ukj, ukj1, ukj2;
    int_t luptr, luptr1, luptr2;
    int fsupc, nsupc, nsupr, segsze;
    int nrow; /* No of rows in the matrix of matrix-vector */
    int jcolp1, jsupno, k, ksub, krep, krep_ind, ksupno;
    int_t lptr, kfnz, isub, irow, i;
    int_t no_zeros, new_next, ufirst, nextlu;
    int fst_col; /* First column within small LU update */
    int d_fsupc; /* Distance between the first column of the current
        panel and the first column of the current snode. */
    int *xsup, *supno;
    int_t *lsub, *xlsub;
    double* lusup;
    int_t* xlusup;
    int_t nzlumax;
    double* tempv1;
    double zero = 0.0;
    double one = 1.0;
    double none = -1.0;
    int_t mem_error;
    flops_t* ops = stat->ops;

    xsup = Glu->xsup;
    supno = Glu->supno;
    lsub = Glu->lsub;
    xlsub = Glu->xlsub;
    lusup = (double*)Glu->lusup;
    xlusup = Glu->xlusup;
    nzlumax = Glu->nzlumax;
    jcolp1 = jcol + 1;
    jsupno = supno[jcol];

    /*
     * For each nonz supernode segment of U[*,j] in topological order
     */
    k = nseg - 1;
    for(ksub = 0; ksub < nseg; ksub++) {
        krep = segrep[k];
        k--;
        ksupno = supno[krep];
        if(jsupno != ksupno) { /* Outside the rectangular supernode */

            fsupc = xsup[ksupno];
            fst_col = SUPERLU_MAX(fsupc, fpanelc);

            /* Distance from the current supernode to the current panel;
               d_fsupc=0 if fsupc > fpanelc. */
            d_fsupc = fst_col - fsupc;

            luptr = xlusup[fst_col] + d_fsupc;
            lptr = xlsub[fsupc] + d_fsupc;

            kfnz = repfnz[krep];
            kfnz = SUPERLU_MAX(kfnz, fpanelc);

            segsze = krep - kfnz + 1;
            nsupc = krep - fst_col + 1;
            nsupr = xlsub[fsupc + 1] - xlsub[fsupc]; /* Leading dimension */
            nrow = nsupr - d_fsupc - nsupc;
            krep_ind = lptr + nsupc - 1;

            ops[TRSV] += segsze * (segsze - 1);
            ops[GEMV] += 2 * nrow * segsze;

            /*
             * Case 1: Update U-segment of size 1 -- col-col update
             */
            if(segsze == 1) {
                ukj = dense[lsub[krep_ind]];
                luptr += nsupr * (nsupc - 1) + nsupc;

                for(i = lptr + nsupc; i < xlsub[fsupc + 1]; ++i) {
                    irow = lsub[i];
                    dense[irow] -= ukj * lusup[luptr];
                    luptr++;
                }
            }
            else if(segsze <= 3) {
                ukj = dense[lsub[krep_ind]];
                luptr += nsupr * (nsupc - 1) + nsupc - 1;
                ukj1 = dense[lsub[krep_ind - 1]];
                luptr1 = luptr - nsupr;

                if(segsze == 2) { /* Case 2: 2cols-col update */
                    ukj -= ukj1 * lusup[luptr1];
                    dense[lsub[krep_ind]] = ukj;
                    for(i = lptr + nsupc; i < xlsub[fsupc + 1]; ++i) {
                        irow = lsub[i];
                        luptr++;
                        luptr1++;
                        dense[irow] -= (ukj * lusup[luptr] + ukj1 * lusup[luptr1]);
                    }
                }
                else { /* Case 3: 3cols-col update */
                    ukj2 = dense[lsub[krep_ind - 2]];
                    luptr2 = luptr1 - nsupr;
                    ukj1 -= ukj2 * lusup[luptr2 - 1];
                    ukj = ukj - ukj1 * lusup[luptr1] - ukj2 * lusup[luptr2];
                    dense[lsub[krep_ind]] = ukj;
                    dense[lsub[krep_ind - 1]] = ukj1;
                    for(i = lptr + nsupc; i < xlsub[fsupc + 1]; ++i) {
                        irow = lsub[i];
                        luptr++;
                        luptr1++;
                        luptr2++;
                        dense[irow] -= (ukj * lusup[luptr] + ukj1 * lusup[luptr1] + ukj2 * lusup[luptr2]);
                    }
                }
            }
            else {
                /*
                 * Case: sup-col update
                 * Perform a triangular solve and block update,
                 * then scatter the result of sup-col update to dense
                 */

                no_zeros = kfnz - fst_col;

                /* Copy U[*,j] segment from dense[*] to tempv[*] */
                isub = lptr + no_zeros;
                for(i = 0; i < segsze; i++) {
                    irow = lsub[isub];
                    tempv[i] = dense[irow];
                    ++isub;
                }

                /* Dense triangular solve -- start effective triangle */
                luptr += nsupr * no_zeros + no_zeros;

#ifdef USE_VENDOR_BLAS
#ifdef _CRAY
                STRSV(ftcs1, ftcs2, ftcs3, &segsze, &lusup[luptr], &nsupr, tempv, &incx);
#else
                dtrsv_("L", "N", "U", &segsze, &lusup[luptr], &nsupr, tempv, &incx);
#endif
                luptr += segsze; /* Dense matrix-vector */
                tempv1 = &tempv[segsze];
                alpha = one;
                beta = zero;
#ifdef _CRAY
                SGEMV(ftcs2, &nrow, &segsze, &alpha, &lusup[luptr], &nsupr, tempv, &incx, &beta, tempv1, &incy);
#else
                dgemv_("N", &nrow, &segsze, &alpha, &lusup[luptr], &nsupr, tempv, &incx, &beta, tempv1, &incy);
#endif
#else
                dlsolve(nsupr, segsze, &lusup[luptr], tempv);

                luptr += segsze; /* Dense matrix-vector */
                tempv1 = &tempv[segsze];
                dmatvec(nsupr, nrow, segsze, &lusup[luptr], tempv, tempv1);
#endif

                /* Scatter tempv[] into SPA dense[] as a temporary storage */
                isub = lptr + no_zeros;
                for(i = 0; i < segsze; i++) {
                    irow = lsub[isub];
                    dense[irow] = tempv[i];
                    tempv[i] = zero;
                    ++isub;
                }

                /* Scatter tempv1[] into SPA dense[] */
                for(i = 0; i < nrow; i++) {
                    irow = lsub[isub];
                    dense[irow] -= tempv1[i];
                    tempv1[i] = zero;
                    ++isub;
                }
            }

        } /* if jsupno ... */

    } /* for each segment... */

    /*
     *	Process the supernodal portion of L\U[*,j]
     */
    nextlu = xlusup[jcol];
    fsupc = xsup[jsupno];

    /* Copy the SPA dense into L\U[*,j] */
    new_next = nextlu + xlsub[fsupc + 1] - xlsub[fsupc];
    while(new_next > nzlumax) {
        mem_error = dLUMemXpand(jcol, nextlu, LUSUP, &nzlumax, Glu);
        if(mem_error) return (mem_error);
        lusup = (double*)Glu->lusup;
        lsub = Glu->lsub;
    }

    for(isub = xlsub[fsupc]; isub < xlsub[fsupc + 1]; isub++) {
        irow = lsub[isub];
        lusup[nextlu] = dense[irow];
        dense[irow] = zero;
        ++nextlu;
    }

    xlusup[jcolp1] = nextlu; /* Close L\U[*,jcol] */

    /* For more updates within the panel (also within the current supernode),
     * should start from the first column of the panel, or the first column
     * of the supernode, whichever is bigger. There are 2 cases:
     *    1) fsupc < fpanelc, then fst_col := fpanelc
     *    2) fsupc >= fpanelc, then fst_col := fsupc
     */
    fst_col = SUPERLU_MAX(fsupc, fpanelc);

    if(fst_col < jcol) {
        /* Distance between the current supernode and the current panel.
           d_fsupc=0 if fsupc >= fpanelc. */
        d_fsupc = fst_col - fsupc;

        lptr = xlsub[fsupc] + d_fsupc;
        luptr = xlusup[fst_col] + d_fsupc;
        nsupr = xlsub[fsupc + 1] - xlsub[fsupc]; /* Leading dimension */
        nsupc = jcol - fst_col;                  /* Excluding jcol */
        nrow = nsupr - d_fsupc - nsupc;

        /* Points to the beginning of jcol in snode L\U(jsupno) */
        ufirst = xlusup[jcol] + d_fsupc;

        ops[TRSV] += nsupc * (nsupc - 1);
        ops[GEMV] += 2 * nrow * nsupc;

#ifdef USE_VENDOR_BLAS
#ifdef _CRAY
        STRSV(ftcs1, ftcs2, ftcs3, &nsupc, &lusup[luptr], &nsupr, &lusup[ufirst], &incx);
#else
        dtrsv_("L", "N", "U", &nsupc, &lusup[luptr], &nsupr, &lusup[ufirst], &incx);
#endif

        alpha = none;
        beta = one; /* y := beta*y + alpha*A*x */

#ifdef _CRAY
        SGEMV(ftcs2, &nrow, &nsupc, &alpha, &lusup[luptr + nsupc], &nsupr, &lusup[ufirst], &incx, &beta, &lusup[ufirst + nsupc], &incy);
#else
        dgemv_("N", &nrow, &nsupc, &alpha, &lusup[luptr + nsupc], &nsupr, &lusup[ufirst], &incx, &beta, &lusup[ufirst + nsupc], &incy);
#endif
#else
        dlsolve(nsupr, nsupc, &lusup[luptr], &lusup[ufirst]);

        dmatvec(nsupr, nrow, nsupc, &lusup[luptr + nsupc], &lusup[ufirst], tempv);

        /* Copy updates from tempv[*] into lusup[*] */
        isub = ufirst + nsupc;
        for(i = 0; i < nrow; i++) {
            lusup[isub] -= tempv[i];
            tempv[i] = 0.0;
            ++isub;
        }

#endif

    } /* if fst_col < jcol ... */

    return 0;
}
