#include "blaswrap.h"
#include "f2c.h"

doublereal dlangb_(char *norm, integer *n, integer *kl, integer *ku, 
	doublereal *ab, integer *ldab, doublereal *work)
{
/*  -- LAPACK auxiliary routine (version 3.1) --   
       Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd..   
       November 2006   


    Purpose   
    =======   

    DLANGB  returns the value of the one norm,  or the Frobenius norm, or   
    the  infinity norm,  or the element of  largest absolute value  of an   
    n by n band matrix  A,  with kl sub-diagonals and ku super-diagonals.   

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

    DLANGB returns the value   

       DLANGB = ( 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 DLANGB as described   
            above.   

    N       (input) INTEGER   
            The order of the matrix A.  N >= 0.  When N = 0, DLANGB is   
            set to zero.   

    KL      (input) INTEGER   
            The number of sub-diagonals of the matrix A.  KL >= 0.   

    KU      (input) INTEGER   
            The number of super-diagonals of the matrix A.  KU >= 0.   

    AB      (input) DOUBLE PRECISION array, dimension (LDAB,N)   
            The band matrix A, stored in rows 1 to KL+KU+1.  The j-th   
            column of A is stored in the j-th column of the array AB as   
            follows:   
            AB(ku+1+i-j,j) = A(i,j) for max(1,j-ku)<=i<=min(n,j+kl).   

    LDAB    (input) INTEGER   
            The leading dimension of the array AB.  LDAB >= KL+KU+1.   

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

   =====================================================================   



       Parameter adjustments */
    /* Table of constant values */
    static integer c__1 = 1;
    
    /* System generated locals */
    integer ab_dim1, ab_offset, i__1, i__2, i__3, i__4, i__5, i__6;
    doublereal ret_val, d__1, d__2, d__3;
    /* Builtin functions */
    double sqrt(doublereal);
    /* Local variables */
    static integer i__, j, k, l;
    static doublereal sum, scale;
    extern logical lsame_(char *, char *);
    static doublereal value;
    extern /* Subroutine */ int dlassq_(integer *, doublereal *, integer *, 
	    doublereal *, doublereal *);


    ab_dim1 = *ldab;
    ab_offset = 1 + ab_dim1;
    ab -= ab_offset;
    --work;

    /* Function Body */
    if (*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) {
/* Computing MAX */
	    i__2 = *ku + 2 - j;
/* Computing MIN */
	    i__4 = *n + *ku + 1 - j, i__5 = *kl + *ku + 1;
	    i__3 = min(i__4,i__5);
	    for (i__ = max(i__2,1); i__ <= i__3; ++i__) {
/* Computing MAX */
		d__2 = value, d__3 = (d__1 = ab[i__ + j * ab_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.;
/* Computing MAX */
	    i__3 = *ku + 2 - j;
/* Computing MIN */
	    i__4 = *n + *ku + 1 - j, i__5 = *kl + *ku + 1;
	    i__2 = min(i__4,i__5);
	    for (i__ = max(i__3,1); i__ <= i__2; ++i__) {
		sum += (d__1 = ab[i__ + j * ab_dim1], abs(d__1));
/* L30: */
	    }
	    value = max(value,sum);
/* L40: */
	}
    } else if (lsame_(norm, "I")) {

/*        Find normI(A). */

	i__1 = *n;
	for (i__ = 1; i__ <= i__1; ++i__) {
	    work[i__] = 0.;
/* L50: */
	}
	i__1 = *n;
	for (j = 1; j <= i__1; ++j) {
	    k = *ku + 1 - j;
/* Computing MAX */
	    i__2 = 1, i__3 = j - *ku;
/* Computing MIN */
	    i__5 = *n, i__6 = j + *kl;
	    i__4 = min(i__5,i__6);
	    for (i__ = max(i__2,i__3); i__ <= i__4; ++i__) {
		work[i__] += (d__1 = ab[k + i__ + j * ab_dim1], abs(d__1));
/* L60: */
	    }
/* L70: */
	}
	value = 0.;
	i__1 = *n;
	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) {
/* Computing MAX */
	    i__4 = 1, i__2 = j - *ku;
	    l = max(i__4,i__2);
	    k = *ku + 1 - j + l;
/* Computing MIN */
	    i__2 = *n, i__3 = j + *kl;
	    i__4 = min(i__2,i__3) - l + 1;
	    dlassq_(&i__4, &ab[k + j * ab_dim1], &c__1, &scale, &sum);
/* L90: */
	}
	value = scale * sqrt(sum);
    }

    ret_val = value;
    return ret_val;

/*     End of DLANGB */

} /* dlangb_ */