#include "clapack.h"

/* Table of constant values */

static integer c__1 = 1;

doublereal dlange_(char *norm, integer *m, integer *n, doublereal *a, integer 
	*lda, doublereal *work)
{
    /* System generated locals */
    integer a_dim1, a_offset, i__1, i__2;
    doublereal ret_val, d__1, d__2, d__3;

    /* Builtin functions */
    double sqrt(doublereal);

    /* Local variables */
    integer i__, j;
    doublereal sum, scale;
    extern logical lsame_(char *, char *);
    doublereal value;
    extern /* Subroutine */ int dlassq_(integer *, doublereal *, integer *, 
	    doublereal *, doublereal *);


/*  -- LAPACK auxiliary routine (version 3.1) -- */
/*     Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd.. */
/*     November 2006 */

/*     .. Scalar Arguments .. */
/*     .. */
/*     .. Array Arguments .. */
/*     .. */

/*  Purpose */
/*  ======= */

/*  DLANGE  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 consistent matrix norm. */

/*  Arguments */
/*  ========= */

/*  NORM    (input) CHARACTER*1 */
/*          Specifies the value to be returned in DLANGE as described */
/*          above. */

/*  M       (input) INTEGER */
/*          The number of rows of the matrix A.  M >= 0.  When M = 0, */
/*          DLANGE is set to zero. */

/*  N       (input) INTEGER */
/*          The number of columns of the matrix A.  N >= 0.  When N = 0, */
/*          DLANGE is set to zero. */

/*  A       (input) DOUBLE PRECISION array, dimension (LDA,N) */
/*          The m by n matrix A. */

/*  LDA     (input) INTEGER */
/*          The leading dimension of the array A.  LDA >= max(M,1). */

/*  WORK    (workspace) DOUBLE PRECISION array, dimension (MAX(1,LWORK)), */
/*          where LWORK >= M when NORM = 'I'; otherwise, WORK is not */
/*          referenced. */

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

/*     .. Parameters .. */
/*     .. */
/*     .. Local Scalars .. */
/*     .. */
/*     .. External Subroutines .. */
/*     .. */
/*     .. External Functions .. */
/*     .. */
/*     .. Intrinsic Functions .. */
/*     .. */
/*     .. Executable Statements .. */

    /* Parameter adjustments */
    a_dim1 = *lda;
    a_offset = 1 + a_dim1;
    a -= a_offset;
    --work;

    /* Function Body */
    if (min(*m,*n) == 0) {
	value = 0.;
    } else if (lsame_(norm, "M")) {

/*        Find max(abs(A(i,j))). */

	value = 0.;
	i__1 = *n;
	for (j = 1; j <= i__1; ++j) {
	    i__2 = *m;
	    for (i__ = 1; i__ <= i__2; ++i__) {
/* Computing MAX */
		d__2 = value, d__3 = (d__1 = a[i__ + j * a_dim1], abs(d__1));
		value = max(d__2,d__3);
/* L10: */
	    }
/* L20: */
	}
    } else if (lsame_(norm, "O") || *(unsigned char *)
	    norm == '1') {

/*        Find norm1(A). */

	value = 0.;
	i__1 = *n;
	for (j = 1; j <= i__1; ++j) {
	    sum = 0.;
	    i__2 = *m;
	    for (i__ = 1; i__ <= i__2; ++i__) {
		sum += (d__1 = a[i__ + j * a_dim1], abs(d__1));
/* L30: */
	    }
	    value = max(value,sum);
/* L40: */
	}
    } else if (lsame_(norm, "I")) {

/*        Find normI(A). */

	i__1 = *m;
	for (i__ = 1; i__ <= i__1; ++i__) {
	    work[i__] = 0.;
/* L50: */
	}
	i__1 = *n;
	for (j = 1; j <= i__1; ++j) {
	    i__2 = *m;
	    for (i__ = 1; i__ <= i__2; ++i__) {
		work[i__] += (d__1 = a[i__ + j * a_dim1], abs(d__1));
/* L60: */
	    }
/* L70: */
	}
	value = 0.;
	i__1 = *m;
	for (i__ = 1; i__ <= i__1; ++i__) {
/* Computing MAX */
	    d__1 = value, d__2 = work[i__];
	    value = max(d__1,d__2);
/* L80: */
	}
    } else if (lsame_(norm, "F") || lsame_(norm, "E")) {

/*        Find normF(A). */

	scale = 0.;
	sum = 1.;
	i__1 = *n;
	for (j = 1; j <= i__1; ++j) {
	    dlassq_(m, &a[j * a_dim1 + 1], &c__1, &scale, &sum);
/* L90: */
	}
	value = scale * sqrt(sum);
    }

    ret_val = value;
    return ret_val;

/*     End of DLANGE */

} /* dlange_ */
