178 lines
4.3 KiB
C
178 lines
4.3 KiB
C
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#include "hypre_lapack.h"
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#include "f2c.h"
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doublereal dlange_(char *norm, integer *m, integer *n, doublereal *a, integer
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*lda, doublereal *work)
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{
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/* -- LAPACK auxiliary routine (version 3.0) --
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Univ. of Tennessee, Univ. of California Berkeley, NAG Ltd.,
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Courant Institute, Argonne National Lab, and Rice University
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October 31, 1992
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Purpose
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=======
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DLANGE returns the value of the one norm, or the Frobenius norm, or
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the infinity norm, or the element of largest absolute value of a
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real matrix A.
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Description
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===========
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DLANGE returns the value
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DLANGE = ( max(abs(A(i,j))), NORM = 'M' or 'm'
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(
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( norm1(A), NORM = '1', 'O' or 'o'
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(
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( normI(A), NORM = 'I' or 'i'
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(
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( normF(A), NORM = 'F', 'f', 'E' or 'e'
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where norm1 denotes the one norm of a matrix (maximum column sum),
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normI denotes the infinity norm of a matrix (maximum row sum) and
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normF denotes the Frobenius norm of a matrix (square root of sum of
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squares). Note that max(abs(A(i,j))) is not a matrix norm.
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Arguments
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=========
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NORM (input) CHARACTER*1
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Specifies the value to be returned in DLANGE as described
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above.
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M (input) INTEGER
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The number of rows of the matrix A. M >= 0. When M = 0,
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DLANGE is set to zero.
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N (input) INTEGER
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The number of columns of the matrix A. N >= 0. When N = 0,
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DLANGE is set to zero.
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A (input) DOUBLE PRECISION array, dimension (LDA,N)
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The m by n matrix A.
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LDA (input) INTEGER
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The leading dimension of the array A. LDA >= max(M,1).
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WORK (workspace) DOUBLE PRECISION array, dimension (LWORK),
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where LWORK >= M when NORM = 'I'; otherwise, WORK is not
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referenced.
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=====================================================================
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Parameter adjustments */
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/* Table of constant values */
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static integer c__1 = 1;
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/* System generated locals */
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integer a_dim1, a_offset, i__1, i__2;
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doublereal ret_val, d__1, d__2, d__3;
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/* Builtin functions */
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double sqrt(doublereal);
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/* Local variables */
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static integer i__, j;
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static doublereal scale;
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extern logical lsame_(char *, char *);
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static doublereal value;
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extern /* Subroutine */ int dlassq_(integer *, doublereal *, integer *,
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doublereal *, doublereal *);
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static doublereal sum;
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#define a_ref(a_1,a_2) a[(a_2)*a_dim1 + a_1]
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a_dim1 = *lda;
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a_offset = 1 + a_dim1 * 1;
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a -= a_offset;
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--work;
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/* Function Body */
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if (min(*m,*n) == 0) {
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value = 0.;
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} else if (lsame_(norm, "M")) {
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/* Find max(abs(A(i,j))). */
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value = 0.;
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i__1 = *n;
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for (j = 1; j <= i__1; ++j) {
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i__2 = *m;
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for (i__ = 1; i__ <= i__2; ++i__) {
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/* Computing MAX */
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d__2 = value, d__3 = (d__1 = a_ref(i__, j), abs(d__1));
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value = max(d__2,d__3);
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/* L10: */
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}
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/* L20: */
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}
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} else if (lsame_(norm, "O") || *(unsigned char *)
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norm == '1') {
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/* Find norm1(A). */
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value = 0.;
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i__1 = *n;
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for (j = 1; j <= i__1; ++j) {
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sum = 0.;
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i__2 = *m;
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for (i__ = 1; i__ <= i__2; ++i__) {
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sum += (d__1 = a_ref(i__, j), abs(d__1));
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/* L30: */
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}
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value = max(value,sum);
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/* L40: */
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}
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} else if (lsame_(norm, "I")) {
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/* Find normI(A). */
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i__1 = *m;
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for (i__ = 1; i__ <= i__1; ++i__) {
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work[i__] = 0.;
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/* L50: */
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}
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i__1 = *n;
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for (j = 1; j <= i__1; ++j) {
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i__2 = *m;
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for (i__ = 1; i__ <= i__2; ++i__) {
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work[i__] += (d__1 = a_ref(i__, j), abs(d__1));
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/* L60: */
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}
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/* L70: */
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}
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value = 0.;
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i__1 = *m;
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for (i__ = 1; i__ <= i__1; ++i__) {
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/* Computing MAX */
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d__1 = value, d__2 = work[i__];
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value = max(d__1,d__2);
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/* L80: */
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}
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} else if (lsame_(norm, "F") || lsame_(norm, "E")) {
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/* Find normF(A). */
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scale = 0.;
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sum = 1.;
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i__1 = *n;
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for (j = 1; j <= i__1; ++j) {
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dlassq_(m, &a_ref(1, j), &c__1, &scale, &sum);
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/* L90: */
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}
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value = scale * sqrt(sum);
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}
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ret_val = value;
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return ret_val;
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/* End of DLANGE */
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} /* dlange_ */
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#undef a_ref
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