/*! \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.
*/

/*
 * -- SuperLU routine (version 3.0) --
 * Lawrence Berkeley National Lab, Univ. of California Berkeley,
 * and Xerox Palo Alto Research Center.
 * September 10, 2007
 *
 */
/*
 * File name:	dlangs.c
 * History:     Modified from lapack routine DLANGE
 */
#include <math.h>
#include "slu_mt_ddefs.h"

double dlangs(char* norm, SuperMatrix* A) {
    /*
        Purpose
        =======

        DLANGS 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
        ===========

        DLANGS returns the value

           DLANGS = ( 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.

       =====================================================================
    */

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

    Astore = A->Store;
    Aval = Astore->nzval;

    if(SUPERLU_MIN(A->nrow, A->ncol) == 0) {
        value = 0.;
    }
    else if(lsame_(norm, "M")) {
        /* 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(lsame_(norm, "O") || *(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(lsame_(norm, "I")) {
        /* Find normI(A). */
        if(!(rwork = (double*)SUPERLU_MALLOC((size_t)A->nrow * sizeof(double))))
            SUPERLU_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(lsame_(norm, "F") || lsame_(norm, "E")) {
        /* Find normF(A). */
        SUPERLU_ABORT("Not implemented.");
    }
    else
        SUPERLU_ABORT("Illegal norm specified.");

    return (value);

} /* dlangs */
