/*! \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
 * \brief Returns the value of the one norm, the infinity norm, or the element of largest value 
 */
 

/*
 * File name:	dlangs.c
 * History:     Modified from lapack routine DLANGE
 */
#include <math.h>
#include "superlu_ddefs.h"

/*! \brief

<pre> 
    Purpose   
    =======   

    DLANGS_dist returns the value of the one norm, or the Frobenius norm, or 
    the infinity norm, or the element of largest absolute value of a 
    real matrix A.   

    Description   
    ===========   

    DLANGE returns the value   

       DLANGE = ( max(abs(A(i,j))), NORM = 'M' or 'm'   
                (   
                ( norm1(A),         NORM = '1', 'O' or 'o'   
                (   
                ( normI(A),         NORM = 'I' or 'i'   
                (   
                ( normF(A),         NORM = 'F', 'f', 'E' or 'e'   

    where  norm1  denotes the  one norm of a matrix (maximum column sum), 
    normI  denotes the  infinity norm  of a matrix  (maximum row sum) and 
    normF  denotes the  Frobenius norm of a matrix (square root of sum of 
    squares).  Note that  max(abs(A(i,j)))  is not a  matrix norm.   

    Arguments   
    =========   

    NORM    (input) CHARACTER*1   
            Specifies the value to be returned in DLANGE as described above.   
    A       (input) SuperMatrix*
            The M by N sparse matrix A. 

   ===================================================================== 
</pre>
*/
double dlangs_dist(char *norm, SuperMatrix *A)
{

    
    /* Local variables */
    NCformat *Astore;
    double   *Aval;
    int_t    i, j, irow;
    double   value=0., sum;
    double   *rwork;

    Astore = (NCformat *) A->Store;
    Aval   = (double *) Astore->nzval;
    
    if ( SUPERLU_MIN(A->nrow, A->ncol) == 0) {
	value = 0.;
	
    } else if ( strncmp(norm, "M", 1)==0 ) {
	/* Find max(abs(A(i,j))). */
	value = 0.;
	for (j = 0; j < A->ncol; ++j)
	    for (i = Astore->colptr[j]; i < Astore->colptr[j+1]; i++)
		value = SUPERLU_MAX( value, fabs( Aval[i]) );
	
    } else if ( strncmp(norm, "O", 1)==0 || *(unsigned char *)norm == '1') {
	/* Find norm1(A). */
	value = 0.;
	for (j = 0; j < A->ncol; ++j) {
	    sum = 0.;
	    for (i = Astore->colptr[j]; i < Astore->colptr[j+1]; i++) 
		sum += fabs(Aval[i]);
	    value = SUPERLU_MAX(value, sum);
	}
	
    } else if ( strncmp(norm, "I", 1)==0 ) {
	/* Find normI(A). */
	if ( !(rwork = (double *) SUPERLU_MALLOC(A->nrow * sizeof(double))) )
	    ABORT("SUPERLU_MALLOC fails for rwork.");
	for (i = 0; i < A->nrow; ++i) rwork[i] = 0.;
	for (j = 0; j < A->ncol; ++j)
	    for (i = Astore->colptr[j]; i < Astore->colptr[j+1]; i++) {
		irow = Astore->rowind[i];
		rwork[irow] += fabs(Aval[i]);
	    }
	value = 0.;
	for (i = 0; i < A->nrow; ++i)
	    value = SUPERLU_MAX(value, rwork[i]);
	
	SUPERLU_FREE (rwork);
	
    } else if ( strncmp(norm, "F", 1)==0 || strncmp(norm, "E", 1)==0 ) {
	/* Find normF(A). */
	ABORT("Not implemented.");
    } else
	ABORT("Illegal norm specified.");

    return (value);

} /* dlangs_dist */

