
/*! @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"

/* 
 * Function prototypes 
 */
void dusolve(int, int, double*, double*);
void dlsolve(int, int, double*, double*);
void dmatvec(int, int, int, double*, double*, double*);



/*! \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          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;
    register int lptr, kfnz, isub, irow, i;
    register int no_zeros, new_next; 
    int          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          *lsub, *xlsub;
    double       *lusup;
    int          *xlusup;
    int          nzlumax;
    double       *tempv1;
    double      zero = 0.0;
    double      one = 1.0;
    double      none = -1.0;
    int          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 ) {
	if (mem_error = dLUMemXpand(jcol, nextlu, LUSUP, &nzlumax, Glu))
	    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;
}
