zlufctr.c

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#include <../../nrnconf.h>
 
/**************************************************************************
**
** Copyright (C) 1993 David E. Steward & Zbigniew Leyk, all rights reserved.
**
**               Meschach Library
** 
** This Meschach Library is provided "as is" without any express 
** or implied warranty of any kind with respect to this software. 
** In particular the authors shall not be liable for any direct, 
** indirect, special, incidental or consequential damages arising 
** in any way from use of the software.
** 
** Everyone is granted permission to copy, modify and redistribute this
** Meschach Library, provided:
**  1.  All copies contain this copyright notice.
**  2.  All modified copies shall carry a notice stating who
**      made the last modification and the date of such modification.
**  3.  No charge is made for this software or works derived from it.  
**      This clause shall not be construed as constraining other software
**      distributed on the same medium as this software, nor is a
**      distribution fee considered a charge.
**
***************************************************************************/
 
/*
    Matrix factorisation routines to work with the other matrix files.
    Complex version
*/
 
static  char    rcsid[] = "zlufctr.c,v 1.1 1997/12/04 17:56:09 hines Exp";
 
#include    <stdio.h>
#include    "zmatrix.h"
#include        "zmatrix2.h"
#include    <math.h>
 
#define is_zero(z)  ((z).re == 0.0 && (z).im == 0.0)
 
 
/* Most matrix factorisation routines are in-situ unless otherwise specified */
 
/* zLUfactor -- Gaussian elimination with scaled partial pivoting
        -- Note: returns LU matrix which is A */
ZMAT    *zLUfactor(A,pivot)
ZMAT    *A;
PERM    *pivot;
{
    u_int   i, j, k, k_max, m, n;
    int i_max;
    Real    dtemp, max1;
    complex **A_v, *A_piv, *A_row, temp;
    static  VEC *scale = VNULL;
 
    if ( A==ZMNULL || pivot==PNULL )
        error(E_NULL,"zLUfactor");
    if ( pivot->size != A->m )
        error(E_SIZES,"zLUfactor");
    m = A->m;   n = A->n;
    scale = v_resize(scale,A->m);
    MEM_STAT_REG(scale,TYPE_VEC);
    A_v = A->me;
 
    /* initialise pivot with identity permutation */
    for ( i=0; i<m; i++ )
        pivot->pe[i] = i;
 
    /* set scale parameters */
    for ( i=0; i<m; i++ )
    {
        max1 = 0.0;
        for ( j=0; j<n; j++ )
        {
            dtemp = zabs(A_v[i][j]);
            max1 = max(max1,dtemp);
        }
        scale->ve[i] = max1;
    }
 
    /* main loop */
    k_max = min(m,n)-1;
    for ( k=0; k<k_max; k++ )
    {
        /* find best pivot row */
        max1 = 0.0; i_max = -1;
        for ( i=k; i<m; i++ )
        if ( scale->ve[i] > 0.0 )
        {
            dtemp = zabs(A_v[i][k])/scale->ve[i];
            if ( dtemp > max1 )
            { max1 = dtemp; i_max = i;  }
        }
        
        /* if no pivot then ignore column k... */
        if ( i_max == -1 )
        continue;
 
        /* do we pivot ? */
        if ( i_max != k )   /* yes we do... */
        {
        px_transp(pivot,i_max,k);
        for ( j=0; j<n; j++ )
        {
            temp = A_v[i_max][j];
            A_v[i_max][j] = A_v[k][j];
            A_v[k][j] = temp;
        }
        }
        
        /* row operations */
        for ( i=k+1; i<m; i++ ) /* for each row do... */
        {   /* Note: divide by zero should never happen */
        temp = A_v[i][k] = zdiv(A_v[i][k],A_v[k][k]);
        A_piv = &(A_v[k][k+1]);
        A_row = &(A_v[i][k+1]);
        temp.re = - temp.re;
        temp.im = - temp.im;
        if ( k+1 < n )
            __zmltadd__(A_row,A_piv,temp,(int)(n-(k+1)),Z_NOCONJ);
        /*********************************************
          for ( j=k+1; j<n; j++ )
          A_v[i][j] -= temp*A_v[k][j];
          (*A_row++) -= temp*(*A_piv++);
        *********************************************/
        }
    }
 
    return A;
}
 
 
/* zLUsolve -- given an LU factorisation in A, solve Ax=b */
ZVEC    *zLUsolve(A,pivot,b,x)
ZMAT    *A;
PERM    *pivot;
ZVEC    *b,*x;
{
    if ( A==ZMNULL || b==ZVNULL || pivot==PNULL )
        error(E_NULL,"zLUsolve");
    if ( A->m != A->n || A->n != b->dim )
        error(E_SIZES,"zLUsolve");
 
    x = px_zvec(pivot,b,x); /* x := P.b */
    zLsolve(A,x,x,1.0); /* implicit diagonal = 1 */
    zUsolve(A,x,x,0.0); /* explicit diagonal */
 
    return (x);
}
 
/* zLUAsolve -- given an LU factorisation in A, solve A^*.x=b */
ZVEC    *zLUAsolve(LU,pivot,b,x)
ZMAT    *LU;
PERM    *pivot;
ZVEC    *b,*x;
{
    if ( ! LU || ! b || ! pivot )
        error(E_NULL,"zLUAsolve");
    if ( LU->m != LU->n || LU->n != b->dim )
        error(E_SIZES,"zLUAsolve");
 
    x = zv_copy(b,x);
    zUAsolve(LU,x,x,0.0);   /* explicit diagonal */
    zLAsolve(LU,x,x,1.0);   /* implicit diagonal = 1 */
    pxinv_zvec(pivot,x,x);  /* x := P^*.x */
 
    return (x);
}
 
/* zm_inverse -- returns inverse of A, provided A is not too rank deficient
    -- uses LU factorisation */
ZMAT    *zm_inverse(A,out)
ZMAT    *A, *out;
{
    int i;
    ZVEC    *tmp, *tmp2;
    ZMAT    *A_cp;
    PERM    *pivot;
 
    if ( ! A )
        error(E_NULL,"zm_inverse");
    if ( A->m != A->n )
        error(E_SQUARE,"zm_inverse");
    if ( ! out || out->m < A->m || out->n < A->n )
        out = zm_resize(out,A->m,A->n);
 
    A_cp = zm_copy(A,ZMNULL);
    tmp = zv_get(A->m);
    tmp2 = zv_get(A->m);
    pivot = px_get(A->m);
    tracecatch(zLUfactor(A_cp,pivot),"zm_inverse");
    for ( i = 0; i < A->n; i++ )
    {
        zv_zero(tmp);
        tmp->ve[i].re = 1.0;
        tmp->ve[i].im = 0.0;
        tracecatch(zLUsolve(A_cp,pivot,tmp,tmp2),"m_inverse");
        zset_col(out,i,tmp2);
    }
 
    ZM_FREE(A_cp);
    ZV_FREE(tmp);   ZV_FREE(tmp2);
    PX_FREE(pivot);
 
    return out;
}
 
/* zLUcondest -- returns an estimate of the condition number of LU given the
    LU factorisation in compact form */
double  zLUcondest(LU,pivot)
ZMAT    *LU;
PERM    *pivot;
{
    static  ZVEC    *y = ZVNULL, *z = ZVNULL;
    Real    cond_est, L_norm, U_norm, norm, sn_inv;
    complex sum;
    int     i, j, n;
 
    if ( ! LU || ! pivot )
    error(E_NULL,"zLUcondest");
    if ( LU->m != LU->n )
    error(E_SQUARE,"zLUcondest");
    if ( LU->n != pivot->size )
    error(E_SIZES,"zLUcondest");
 
    n = LU->n;
    y = zv_resize(y,n);
    z = zv_resize(z,n);
    MEM_STAT_REG(y,TYPE_ZVEC);
    MEM_STAT_REG(z,TYPE_ZVEC);
 
    cond_est = 0.0;     /* should never be returned */
 
    for ( i = 0; i < n; i++ )
    {
    sum.re = 1.0;
    sum.im = 0.0;
    for ( j = 0; j < i; j++ )
        /* sum -= LU->me[j][i]*y->ve[j]; */
        sum = zsub(sum,zmlt(LU->me[j][i],y->ve[j]));
    /* sum -= (sum < 0.0) ? 1.0 : -1.0; */
    sn_inv = 1.0 / zabs(sum);
    sum.re += sum.re * sn_inv;
    sum.im += sum.im * sn_inv;
    if ( is_zero(LU->me[i][i]) )
        return HUGE;
    /* y->ve[i] = sum / LU->me[i][i]; */
    y->ve[i] = zdiv(sum,LU->me[i][i]);
    }
 
    zLAsolve(LU,y,y,1.0);
    zLUsolve(LU,pivot,y,z);
 
    /* now estimate norm of A (even though it is not directly available) */
    /* actually computes ||L||_inf.||U||_inf */
    U_norm = 0.0;
    for ( i = 0; i < n; i++ )
    {
    norm = 0.0;
    for ( j = i; j < n; j++ )
        norm += zabs(LU->me[i][j]);
    if ( norm > U_norm )
        U_norm = norm;
    }
    L_norm = 0.0;
    for ( i = 0; i < n; i++ )
    {
    norm = 1.0;
    for ( j = 0; j < i; j++ )
        norm += zabs(LU->me[i][j]);
    if ( norm > L_norm )
        L_norm = norm;
    }
 
    tracecatch(cond_est = U_norm*L_norm*zv_norm_inf(z)/zv_norm_inf(y),
           "LUcondest");
 
    return cond_est;
}