59 lines
1.4 KiB
C++
59 lines
1.4 KiB
C++
#ifdef __cplusplus
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extern "C" {
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#endif
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#include "lmp_f2c.h"
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doublereal ddot_(integer *n, doublereal *dx, integer *incx, doublereal *dy, integer *incy)
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{
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integer i__1;
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doublereal ret_val;
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integer i__, m, ix, iy, mp1;
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doublereal dtemp;
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--dy;
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--dx;
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ret_val = 0.;
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dtemp = 0.;
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if (*n <= 0) {
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return ret_val;
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}
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if (*incx == 1 && *incy == 1) {
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m = *n % 5;
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if (m != 0) {
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i__1 = m;
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for (i__ = 1; i__ <= i__1; ++i__) {
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dtemp += dx[i__] * dy[i__];
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}
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if (*n < 5) {
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ret_val = dtemp;
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return ret_val;
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}
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}
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mp1 = m + 1;
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i__1 = *n;
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for (i__ = mp1; i__ <= i__1; i__ += 5) {
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dtemp = dtemp + dx[i__] * dy[i__] + dx[i__ + 1] * dy[i__ + 1] +
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dx[i__ + 2] * dy[i__ + 2] + dx[i__ + 3] * dy[i__ + 3] +
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dx[i__ + 4] * dy[i__ + 4];
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}
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} else {
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ix = 1;
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iy = 1;
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if (*incx < 0) {
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ix = (-(*n) + 1) * *incx + 1;
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}
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if (*incy < 0) {
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iy = (-(*n) + 1) * *incy + 1;
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}
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i__1 = *n;
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for (i__ = 1; i__ <= i__1; ++i__) {
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dtemp += dx[ix] * dy[iy];
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ix += *incx;
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iy += *incy;
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}
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}
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ret_val = dtemp;
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return ret_val;
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}
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#ifdef __cplusplus
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}
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#endif
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