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171 lines
4.6 KiB
C
171 lines
4.6 KiB
C
#include "clapack.h"
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/* Table of constant values */
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static doublereal c_b7 = 1.;
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static integer c__1 = 1;
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/* Subroutine */ int dlauu2_(char *uplo, integer *n, doublereal *a, integer *
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lda, integer *info)
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{
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/* System generated locals */
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integer a_dim1, a_offset, i__1, i__2, i__3;
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/* Local variables */
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integer i__;
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doublereal aii;
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extern doublereal ddot_(integer *, doublereal *, integer *, doublereal *,
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integer *);
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extern /* Subroutine */ int dscal_(integer *, doublereal *, doublereal *,
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integer *);
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extern logical lsame_(char *, char *);
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extern /* Subroutine */ int dgemv_(char *, integer *, integer *,
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doublereal *, doublereal *, integer *, doublereal *, integer *,
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doublereal *, doublereal *, integer *);
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logical upper;
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extern /* Subroutine */ int xerbla_(char *, integer *);
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/* -- LAPACK auxiliary routine (version 3.1) -- */
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/* Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd.. */
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/* November 2006 */
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/* .. Scalar Arguments .. */
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/* .. */
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/* .. Array Arguments .. */
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/* .. */
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/* Purpose */
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/* ======= */
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/* DLAUU2 computes the product U * U' or L' * L, where the triangular */
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/* factor U or L is stored in the upper or lower triangular part of */
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/* the array A. */
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/* If UPLO = 'U' or 'u' then the upper triangle of the result is stored, */
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/* overwriting the factor U in A. */
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/* If UPLO = 'L' or 'l' then the lower triangle of the result is stored, */
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/* overwriting the factor L in A. */
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/* This is the unblocked form of the algorithm, calling Level 2 BLAS. */
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/* Arguments */
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/* ========= */
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/* UPLO (input) CHARACTER*1 */
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/* Specifies whether the triangular factor stored in the array A */
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/* is upper or lower triangular: */
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/* = 'U': Upper triangular */
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/* = 'L': Lower triangular */
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/* N (input) INTEGER */
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/* The order of the triangular factor U or L. N >= 0. */
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/* A (input/output) DOUBLE PRECISION array, dimension (LDA,N) */
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/* On entry, the triangular factor U or L. */
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/* On exit, if UPLO = 'U', the upper triangle of A is */
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/* overwritten with the upper triangle of the product U * U'; */
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/* if UPLO = 'L', the lower triangle of A is overwritten with */
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/* the lower triangle of the product L' * L. */
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/* LDA (input) INTEGER */
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/* The leading dimension of the array A. LDA >= max(1,N). */
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/* INFO (output) INTEGER */
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/* = 0: successful exit */
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/* < 0: if INFO = -k, the k-th argument had an illegal value */
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/* ===================================================================== */
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/* .. Parameters .. */
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/* .. */
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/* .. Local Scalars .. */
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/* .. */
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/* .. External Functions .. */
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/* .. */
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/* .. External Subroutines .. */
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/* .. */
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/* .. Intrinsic Functions .. */
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/* .. */
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/* .. Executable Statements .. */
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/* Test the input parameters. */
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/* Parameter adjustments */
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a_dim1 = *lda;
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a_offset = 1 + a_dim1;
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a -= a_offset;
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/* Function Body */
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*info = 0;
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upper = lsame_(uplo, "U");
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if (! upper && ! lsame_(uplo, "L")) {
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*info = -1;
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} else if (*n < 0) {
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*info = -2;
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} else if (*lda < max(1,*n)) {
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*info = -4;
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}
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if (*info != 0) {
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i__1 = -(*info);
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xerbla_("DLAUU2", &i__1);
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return 0;
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}
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/* Quick return if possible */
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if (*n == 0) {
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return 0;
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}
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if (upper) {
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/* Compute the product U * U'. */
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i__1 = *n;
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for (i__ = 1; i__ <= i__1; ++i__) {
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aii = a[i__ + i__ * a_dim1];
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if (i__ < *n) {
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i__2 = *n - i__ + 1;
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a[i__ + i__ * a_dim1] = ddot_(&i__2, &a[i__ + i__ * a_dim1],
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lda, &a[i__ + i__ * a_dim1], lda);
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i__2 = i__ - 1;
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i__3 = *n - i__;
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dgemv_("No transpose", &i__2, &i__3, &c_b7, &a[(i__ + 1) *
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a_dim1 + 1], lda, &a[i__ + (i__ + 1) * a_dim1], lda, &
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aii, &a[i__ * a_dim1 + 1], &c__1);
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} else {
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dscal_(&i__, &aii, &a[i__ * a_dim1 + 1], &c__1);
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}
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/* L10: */
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}
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} else {
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/* Compute the product L' * L. */
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i__1 = *n;
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for (i__ = 1; i__ <= i__1; ++i__) {
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aii = a[i__ + i__ * a_dim1];
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if (i__ < *n) {
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i__2 = *n - i__ + 1;
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a[i__ + i__ * a_dim1] = ddot_(&i__2, &a[i__ + i__ * a_dim1], &
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c__1, &a[i__ + i__ * a_dim1], &c__1);
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i__2 = *n - i__;
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i__3 = i__ - 1;
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dgemv_("Transpose", &i__2, &i__3, &c_b7, &a[i__ + 1 + a_dim1],
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lda, &a[i__ + 1 + i__ * a_dim1], &c__1, &aii, &a[i__
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+ a_dim1], lda);
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} else {
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dscal_(&i__, &aii, &a[i__ + a_dim1], lda);
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}
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/* L20: */
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}
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}
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return 0;
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/* End of DLAUU2 */
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} /* dlauu2_ */
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