114 lines
2.6 KiB
C
114 lines
2.6 KiB
C
#include "blaswrap.h"
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#ifdef _cpluscplus
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extern "C" {
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#endif
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#include "f2c.h"
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/* Subroutine */ int drscl_(integer *n, doublereal *sa, doublereal *sx,
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integer *incx)
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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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September 30, 1994
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Purpose
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=======
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DRSCL multiplies an n-element real vector x by the real scalar 1/a.
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This is done without overflow or underflow as long as
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the final result x/a does not overflow or underflow.
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Arguments
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=========
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N (input) INTEGER
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The number of components of the vector x.
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SA (input) DOUBLE PRECISION
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The scalar a which is used to divide each component of x.
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SA must be >= 0, or the subroutine will divide by zero.
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SX (input/output) DOUBLE PRECISION array, dimension
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(1+(N-1)*abs(INCX))
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The n-element vector x.
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INCX (input) INTEGER
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The increment between successive values of the vector SX.
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> 0: SX(1) = X(1) and SX(1+(i-1)*INCX) = x(i), 1< i<= n
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=====================================================================
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Quick return if possible
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Parameter adjustments */
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static doublereal cden;
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static logical done;
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static doublereal cnum, cden1, cnum1;
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extern /* Subroutine */ int dscal_(integer *, doublereal *, doublereal *,
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integer *), dlabad_(doublereal *, doublereal *);
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extern doublereal dlamch_(char *);
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static doublereal bignum, smlnum, mul;
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--sx;
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/* Function Body */
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if (*n <= 0) {
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return 0;
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}
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/* Get machine parameters */
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smlnum = dlamch_("S");
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bignum = 1. / smlnum;
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dlabad_(&smlnum, &bignum);
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/* Initialize the denominator to SA and the numerator to 1. */
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cden = *sa;
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cnum = 1.;
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L10:
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cden1 = cden * smlnum;
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cnum1 = cnum / bignum;
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if (abs(cden1) > abs(cnum) && cnum != 0.) {
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/* Pre-multiply X by SMLNUM if CDEN is large compared to CNUM. */
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mul = smlnum;
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done = FALSE_;
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cden = cden1;
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} else if (abs(cnum1) > abs(cden)) {
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/* Pre-multiply X by BIGNUM if CDEN is small compared to CNUM. */
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mul = bignum;
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done = FALSE_;
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cnum = cnum1;
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} else {
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/* Multiply X by CNUM / CDEN and return. */
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mul = cnum / cden;
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done = TRUE_;
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}
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/* Scale the vector X by MUL */
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dscal_(n, &mul, &sx[1], incx);
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if (! done) {
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goto L10;
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}
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return 0;
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/* End of DRSCL */
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} /* drscl_ */
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#ifdef _cpluscplus
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}
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#endif
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