/*! @file ilu_dcopy_to_ucol.c

 * \brief Copy a computed column of U to the compressed data structure

 * and drop some small entries

 *

 * 

 * -- SuperLU routine (version 4.1) --

 * Lawrence Berkeley National Laboratory

 * November, 2010

 * 

 */

#include "slu_ddefs.h"

#ifdef DEBUG

int num_drop_U;

#endif

extern void dcopy_(int *, double [], int *, double [], int *);

#if 0

static double *A;  /* used in _compare_ only */

static int _compare_(const void *a, const void *b)

{

    register int *x = (int *)a, *y = (int *)b;

    register double xx = fabs(A[*x]), yy = fabs(A[*y]);

    if (xx > yy) return -1;

    else if (xx < yy) return 1;

    else return 0;

}

#endif

int

ilu_dcopy_to_ucol(

	      int	 jcol,	   /* in */

	      int	 nseg,	   /* in */

	      int	 *segrep,  /* in */

	      int	 *repfnz,  /* in */

	      int	 *perm_r,  /* in */

	      double	 *dense,   /* modified - reset to zero on return */

	      int  	 drop_rule,/* in */

	      milu_t	 milu,	   /* in */

	      double	 drop_tol, /* in */

	      int	 quota,    /* maximum nonzero entries allowed */

	      double	 *sum,	   /* out - the sum of dropped entries */

	      int	 *nnzUj,   /* in - out */

	      GlobalLU_t *Glu,	   /* modified */

	      double	 *work	   /* working space with minimum size n,

				    * used by the second dropping rule */

	      )

{

/*

 * Gather from SPA dense[*] to global ucol[*].

 */

    int       ksub, krep, ksupno;

    int       i, k, kfnz, segsze;

    int       fsupc, isub, irow;

    int       jsupno, nextu;

    int       new_next, mem_error;

    int       *xsup, *supno;

    int       *lsub, *xlsub;

    double    *ucol;

    int       *usub, *xusub;

    int       nzumax;

    int       m; /* number of entries in the nonzero U-segments */

    register double d_max = 0.0, d_min = 1.0 / dlamch_("Safe minimum");

    register double tmp;

    double zero = 0.0;

    int i_1 = 1;

    xsup    = Glu->xsup;

    supno   = Glu->supno;

    lsub    = Glu->lsub;

    xlsub   = Glu->xlsub;

    ucol    = Glu->ucol;

    usub    = Glu->usub;

    xusub   = Glu->xusub;

    nzumax  = Glu->nzumax;

    *sum = zero;

    if (drop_rule == NODROP) {

	drop_tol = -1.0, quota = Glu->n;

    }

    jsupno = supno[jcol];

    nextu  = xusub[jcol];

    k = nseg - 1;

    for (ksub = 0; ksub < nseg; ksub++) {

	krep = segrep[k--];

	ksupno = supno[krep];

	if ( ksupno != jsupno ) { /* Should go into ucol[] */

	    kfnz = repfnz[krep];

	    if ( kfnz != EMPTY ) {	/* Nonzero U-segment */

		fsupc = xsup[ksupno];

		isub = xlsub[fsupc] + kfnz - fsupc;

		segsze = krep - kfnz + 1;

		new_next = nextu + segsze;

		while ( new_next > nzumax ) {

		    if ((mem_error = dLUMemXpand(jcol, nextu, UCOL, &nzumax,

			    Glu)) != 0)

			return (mem_error);

		    ucol = Glu->ucol;

		    if ((mem_error = dLUMemXpand(jcol, nextu, USUB, &nzumax,

			    Glu)) != 0)

			return (mem_error);

		    usub = Glu->usub;

		    lsub = Glu->lsub;

		}

		for (i = 0; i < segsze; i++) {

		    irow = lsub[isub++];

		    tmp = fabs(dense[irow]);

		    /* first dropping rule */

		    if (quota > 0 && tmp >= drop_tol) {

			if (tmp > d_max) d_max = tmp;

			if (tmp < d_min) d_min = tmp;

			usub[nextu] = perm_r[irow];

			ucol[nextu] = dense[irow];

			nextu++;

		    } else {

			switch (milu) {

			    case SMILU_1:

			    case SMILU_2:

				*sum += dense[irow];

				break;

			    case SMILU_3:

				/* *sum += fabs(dense[irow]);*/

				*sum += tmp;

				break;

			    case SILU:

			    default:

				break;

			}

#ifdef DEBUG

			num_drop_U++;

#endif

		    }

		    dense[irow] = zero;

		}

	    }

	}

    } /* for each segment... */

    xusub[jcol + 1] = nextu;	  /* Close U[*,jcol] */

    m = xusub[jcol + 1] - xusub[jcol];

    /* second dropping rule */

    if (drop_rule & DROP_SECONDARY && m > quota) {

	register double tol = d_max;

	register int m0 = xusub[jcol] + m - 1;

	if (quota > 0) {

	    if (drop_rule & DROP_INTERP) {

		d_max = 1.0 / d_max; d_min = 1.0 / d_min;

		tol = 1.0 / (d_max + (d_min - d_max) * quota / m);

	    } else {

		dcopy_(&m, &ucol[xusub[jcol]], &i_1, work, &i_1);

		tol = dqselect(m, work, quota);

#if 0

		A = &ucol[xusub[jcol]];

		for (i = 0; i < m; i++) work[i] = i;

		qsort(work, m, sizeof(int), _compare_);

		tol = fabs(usub[xusub[jcol] + work[quota]]);

#endif

	    }

	}

	for (i = xusub[jcol]; i <= m0; ) {

	    if (fabs(ucol[i]) <= tol) {

		switch (milu) {

		    case SMILU_1:

		    case SMILU_2:

			*sum += ucol[i];

			break;

		    case SMILU_3:

			*sum += fabs(ucol[i]);

			break;

		    case SILU:

		    default:

			break;

		}

		ucol[i] = ucol[m0];

		usub[i] = usub[m0];

		m0--;

		m--;

#ifdef DEBUG

		num_drop_U++;

#endif

		xusub[jcol + 1]--;

		continue;

	    }

	    i++;

	}

    }

    if (milu == SMILU_2) *sum = fabs(*sum);

    *nnzUj += m;

    return 0;

}