norm.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.
**
***************************************************************************/


/*
    A collection of functions for computing norms: scaled and unscaled
*/
static  char    rcsid[] = "norm.c,v 1.1 1997/12/04 17:55:43 hines Exp";

#include    <stdio.h>
#include    "matrix.h"
#include    <math.h>


/* _v_norm1 -- computes (scaled) 1-norms of vectors */
double  _v_norm1(x,scale)
VEC *x, *scale;
{
    int i, dim;
    Real    s, sum;

    if ( x == (VEC *)NULL )
        error(E_NULL,"_v_norm1");
    dim = x->dim;

    sum = 0.0;
    if ( scale == (VEC *)NULL )
        for ( i = 0; i < dim; i++ )
            sum += fabs(x->ve[i]);
    else if ( scale->dim < dim )
        error(E_SIZES,"_v_norm1");
    else
        for ( i = 0; i < dim; i++ )
        {   s = scale->ve[i];
            sum += ( s== 0.0 ) ? fabs(x->ve[i]) : fabs(x->ve[i]/s);
        }

    return sum;
}

/* square -- returns x^2 */
double  square(x)
double  x;
{   return x*x; }

/* cube -- returns x^3 */
double cube(x)
double x;
{  return x*x*x;   }

/* _v_norm2 -- computes (scaled) 2-norm (Euclidean norm) of vectors */
double  _v_norm2(x,scale)
VEC *x, *scale;
{
    int i, dim;
    Real    s, sum;

    if ( x == (VEC *)NULL )
        error(E_NULL,"_v_norm2");
    dim = x->dim;

    sum = 0.0;
    if ( scale == (VEC *)NULL )
        for ( i = 0; i < dim; i++ )
            sum += square(x->ve[i]);
    else if ( scale->dim < dim )
        error(E_SIZES,"_v_norm2");
    else
        for ( i = 0; i < dim; i++ )
        {   s = scale->ve[i];
            sum += ( s== 0.0 ) ? square(x->ve[i]) :
                            square(x->ve[i]/s);
        }

    return sqrt(sum);
}

#define max(a,b)    ((a) > (b) ? (a) : (b))

/* _v_norm_inf -- computes (scaled) infinity-norm (supremum norm) of vectors */
double  _v_norm_inf(x,scale)
VEC *x, *scale;
{
    int i, dim;
    Real    s, maxval, tmp;

    if ( x == (VEC *)NULL )
        error(E_NULL,"_v_norm_inf");
    dim = x->dim;

    maxval = 0.0;
    if ( scale == (VEC *)NULL )
        for ( i = 0; i < dim; i++ )
        {   tmp = fabs(x->ve[i]);
            maxval = max(maxval,tmp);
        }
    else if ( scale->dim < dim )
        error(E_SIZES,"_v_norm_inf");
    else
        for ( i = 0; i < dim; i++ )
        {   s = scale->ve[i];
            tmp = ( s== 0.0 ) ? fabs(x->ve[i]) : fabs(x->ve[i]/s);
            maxval = max(maxval,tmp);
        }

    return maxval;
}

/* m_norm1 -- compute matrix 1-norm -- unscaled */
double  m_norm1(A)
MAT *A;
{
    int i, j, m, n;
    Real    maxval, sum;

    if ( A == (MAT *)NULL )
        error(E_NULL,"m_norm1");

    m = A->m;   n = A->n;
    maxval = 0.0;

    for ( j = 0; j < n; j++ )
    {
        sum = 0.0;
        for ( i = 0; i < m; i ++ )
            sum += fabs(A->me[i][j]);
        maxval = max(maxval,sum);
    }

    return maxval;
}

/* m_norm_inf -- compute matrix infinity-norm -- unscaled */
double  m_norm_inf(A)
MAT *A;
{
    int i, j, m, n;
    Real    maxval, sum;

    if ( A == (MAT *)NULL )
        error(E_NULL,"m_norm_inf");

    m = A->m;   n = A->n;
    maxval = 0.0;

    for ( i = 0; i < m; i++ )
    {
        sum = 0.0;
        for ( j = 0; j < n; j ++ )
            sum += fabs(A->me[i][j]);
        maxval = max(maxval,sum);
    }

    return maxval;
}

/* m_norm_frob -- compute matrix frobenius-norm -- unscaled */
double  m_norm_frob(A)
MAT *A;
{
    int i, j, m, n;
    Real    sum;

    if ( A == (MAT *)NULL )
        error(E_NULL,"m_norm_frob");

    m = A->m;   n = A->n;
    sum = 0.0;

    for ( i = 0; i < m; i++ )
        for ( j = 0; j < n; j ++ )
            sum += square(A->me[i][j]);

    return sqrt(sum);
}