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81 lines
1.8 KiB
C++
81 lines
1.8 KiB
C++
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template <typename Scalar>
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void ei_rwupdt(int n, Scalar *r__, int ldr,
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const Scalar *w, Scalar *b, Scalar *alpha, Scalar *cos__,
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Scalar *sin__)
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{
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/* System generated locals */
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int r_dim1, r_offset;
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/* Local variables */
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int i, j, jm1;
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Scalar tan__, temp, rowj, cotan;
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/* Parameter adjustments */
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--sin__;
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--cos__;
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--b;
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--w;
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r_dim1 = ldr;
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r_offset = 1 + r_dim1 * 1;
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r__ -= r_offset;
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/* Function Body */
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for (j = 1; j <= n; ++j) {
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rowj = w[j];
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jm1 = j - 1;
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/* apply the previous transformations to */
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/* r(i,j), i=1,2,...,j-1, and to w(j). */
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if (jm1 < 1) {
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goto L20;
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}
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for (i = 1; i <= jm1; ++i) {
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temp = cos__[i] * r__[i + j * r_dim1] + sin__[i] * rowj;
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rowj = -sin__[i] * r__[i + j * r_dim1] + cos__[i] * rowj;
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r__[i + j * r_dim1] = temp;
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/* L10: */
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}
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L20:
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/* determine a givens rotation which eliminates w(j). */
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cos__[j] = 1.;
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sin__[j] = 0.;
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if (rowj == 0.) {
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goto L50;
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}
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if (ei_abs(r__[j + j * r_dim1]) >= ei_abs(rowj))
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goto L30;
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cotan = r__[j + j * r_dim1] / rowj;
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/* Computing 2nd power */
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sin__[j] = Scalar(.5) / ei_sqrt(Scalar(0.25) + Scalar(0.25) * ei_abs2(cotan));
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cos__[j] = sin__[j] * cotan;
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goto L40;
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L30:
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tan__ = rowj / r__[j + j * r_dim1];
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/* Computing 2nd power */
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cos__[j] = Scalar(.5) / ei_sqrt(Scalar(0.25) + Scalar(0.25) * ei_abs2(tan__));
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sin__[j] = cos__[j] * tan__;
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L40:
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/* apply the current transformation to r(j,j), b(j), and alpha. */
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r__[j + j * r_dim1] = cos__[j] * r__[j + j * r_dim1] + sin__[j] *
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rowj;
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temp = cos__[j] * b[j] + sin__[j] * *alpha;
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*alpha = -sin__[j] * b[j] + cos__[j] * *alpha;
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b[j] = temp;
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L50:
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/* L60: */
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;
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}
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return;
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/* last card of subroutine rwupdt. */
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} /* rwupdt_ */
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