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/* laso/dlabax.f -- translated by f2c (version 20050501).
You must link the resulting object file with libf2c:
on Microsoft Windows system, link with libf2c.lib;
on Linux or Unix systems, link with .../path/to/libf2c.a -lm
or, if you install libf2c.a in a standard place, with -lf2c -lm
-- in that order, at the end of the command line, as in
cc *.o -lf2c -lm
Source for libf2c is in /netlib/f2c/libf2c.zip, e.g.,
http://www.netlib.org/f2c/libf2c.zip
*/
#ifdef __cplusplus
extern "C" {
#endif
#include "v3p_netlib.h"
/* Table of constant values */
static integer c__0 = 0;
static integer c__1 = 1;
/* *********************************************************************** */
/*< SUBROUTINE DLABAX(N, NBAND, A, X, Y) >*/
/* Subroutine */ int dlabax_(integer *n, integer *nband, doublereal *a,
doublereal *x, doublereal *y)
{
/* System generated locals */
integer a_dim1, a_offset, i__1, i__2;
/* Local variables */
integer i__, k, l, m;
doublereal zero[1];
extern /* Subroutine */ int dcopy_(integer *, doublereal *, integer *,
doublereal *, integer *);
/* THIS SUBROUTINE SETS Y = A*X */
/* WHERE X AND Y ARE VECTORS OF LENGTH N */
/* AND A IS AN N X NBAND SYMMETRIC BAND MATRIX */
/* FORMAL PARAMETERS */
/*< INTEGER N, NBAND >*/
/*< DOUBLE PRECISION A(NBAND,1), X(1), Y(1) >*/
/* LOCAL VARIABLES */
/*< INTEGER I, K, L, M >*/
/*< DOUBLE PRECISION ZERO(1) >*/
/* FUNCTIONS CALLED */
/*< INTEGER MIN0 >*/
/* SUBROUTINES CALLED */
/* DCOPY */
/*< ZERO(1) = 0.0D0 >*/
/* Parameter adjustments */
a_dim1 = *nband;
a_offset = 1 + a_dim1;
a -= a_offset;
--x;
--y;
/* Function Body */
zero[0] = 0.;
/*< CALL DCOPY(N, ZERO, 0, Y, 1) >*/
dcopy_(n, zero, &c__0, &y[1], &c__1);
/*< DO 20 K = 1, N >*/
i__1 = *n;
for (k = 1; k <= i__1; ++k) {
/*< Y(K) = Y(K) + A(1,K)*X(K) >*/
y[k] += a[k * a_dim1 + 1] * x[k];
/*< M = MIN0(N-K+1, NBAND) >*/
/* Computing MIN */
i__2 = *n - k + 1;
m = min(i__2,*nband);
/*< IF(M .LT. 2) GO TO 20 >*/
if (m < 2) {
goto L20;
}
/*< DO 10 I = 2, M >*/
i__2 = m;
for (i__ = 2; i__ <= i__2; ++i__) {
/*< L = K + I - 1 >*/
l = k + i__ - 1;
/*< Y(L) = Y(L) + A(I,K)*X(K) >*/
y[l] += a[i__ + k * a_dim1] * x[k];
/*< Y(K) = Y(K) + A(I,K)*X(L) >*/
y[k] += a[i__ + k * a_dim1] * x[l];
/*< 10 CONTINUE >*/
/* L10: */
}
/*< 20 CONTINUE >*/
L20:
;
}
/*< RETURN >*/
return 0;
/*< END >*/
} /* dlabax_ */
#ifdef __cplusplus
}
#endif
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