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/* eispack/rebak.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"
/*< subroutine rebak(nm,n,b,dl,m,z) >*/
/* Subroutine */ int rebak_(integer *nm, integer *n, doublereal *b,
doublereal *dl, integer *m, doublereal *z__)
{
/* System generated locals */
integer b_dim1, b_offset, z_dim1, z_offset, i__1, i__2, i__3;
/* Local variables */
integer i__, j, k;
doublereal x;
integer i1, ii;
/*< integer i,j,k,m,n,i1,ii,nm >*/
/*< double precision b(nm,n),dl(n),z(nm,m) >*/
/*< double precision x >*/
/* this subroutine is a translation of the algol procedure rebaka, */
/* num. math. 11, 99-110(1968) by martin and wilkinson. */
/* handbook for auto. comp., vol.ii-linear algebra, 303-314(1971). */
/* this subroutine forms the eigenvectors of a generalized */
/* symmetric eigensystem by back transforming those of the */
/* derived symmetric matrix determined by reduc. */
/* on input */
/* nm must be set to the row dimension of two-dimensional */
/* array parameters as declared in the calling program */
/* dimension statement. */
/* n is the order of the matrix system. */
/* b contains information about the similarity transformation */
/* (cholesky decomposition) used in the reduction by reduc */
/* in its strict lower triangle. */
/* dl contains further information about the transformation. */
/* m is the number of eigenvectors to be back transformed. */
/* z contains the eigenvectors to be back transformed */
/* in its first m columns. */
/* on output */
/* z contains the transformed eigenvectors */
/* in its first m columns. */
/* questions and comments should be directed to burton s. garbow, */
/* mathematics and computer science div, argonne national laboratory */
/* this version dated august 1983. */
/* ------------------------------------------------------------------ */
/*< if (m .eq. 0) go to 200 >*/
/* Parameter adjustments */
--dl;
b_dim1 = *nm;
b_offset = 1 + b_dim1;
b -= b_offset;
z_dim1 = *nm;
z_offset = 1 + z_dim1;
z__ -= z_offset;
/* Function Body */
if (*m == 0) {
goto L200;
}
/*< do 100 j = 1, m >*/
i__1 = *m;
for (j = 1; j <= i__1; ++j) {
/* .......... for i=n step -1 until 1 do -- .......... */
/*< do 100 ii = 1, n >*/
i__2 = *n;
for (ii = 1; ii <= i__2; ++ii) {
/*< i = n + 1 - ii >*/
i__ = *n + 1 - ii;
/*< i1 = i + 1 >*/
i1 = i__ + 1;
/*< x = z(i,j) >*/
x = z__[i__ + j * z_dim1];
/*< if (i .eq. n) go to 80 >*/
if (i__ == *n) {
goto L80;
}
/*< do 60 k = i1, n >*/
i__3 = *n;
for (k = i1; k <= i__3; ++k) {
/*< 60 x = x - b(k,i) * z(k,j) >*/
/* L60: */
x -= b[k + i__ * b_dim1] * z__[k + j * z_dim1];
}
/*< 80 z(i,j) = x / dl(i) >*/
L80:
z__[i__ + j * z_dim1] = x / dl[i__];
/*< 100 continue >*/
/* L100: */
}
}
/*< 200 return >*/
L200:
return 0;
/*< end >*/
} /* rebak_ */
#ifdef __cplusplus
}
#endif
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