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/* eispack/elmhes.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 elmhes(nm,n,low,igh,a,int) >*/
/* Subroutine */ int elmhes_(integer *nm, integer *n, integer *low, integer *
igh, doublereal *a, integer *int__)
{
/* System generated locals */
integer a_dim1, a_offset, i__1, i__2, i__3;
doublereal d__1;
/* Local variables */
integer i__, j, m;
doublereal x, y;
integer la, mm1, kp1, mp1;
/*< integer i,j,m,n,la,nm,igh,kp1,low,mm1,mp1 >*/
/*< double precision a(nm,n) >*/
/*< double precision x,y >*/
/*< integer int(igh) >*/
/* this subroutine is a translation of the algol procedure elmhes, */
/* num. math. 12, 349-368(1968) by martin and wilkinson. */
/* handbook for auto. comp., vol.ii-linear algebra, 339-358(1971). */
/* given a real general matrix, this subroutine */
/* reduces a submatrix situated in rows and columns */
/* low through igh to upper hessenberg form by */
/* stabilized elementary similarity transformations. */
/* 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. */
/* low and igh are integers determined by the balancing */
/* subroutine balanc. if balanc has not been used, */
/* set low=1, igh=n. */
/* a contains the input matrix. */
/* on output */
/* a contains the hessenberg matrix. the multipliers */
/* which were used in the reduction are stored in the */
/* remaining triangle under the hessenberg matrix. */
/* int contains information on the rows and columns */
/* interchanged in the reduction. */
/* only elements low through igh are used. */
/* questions and comments should be directed to burton s. garbow, */
/* mathematics and computer science div, argonne national laboratory */
/* this version dated august 1983. */
/* ------------------------------------------------------------------ */
/*< la = igh - 1 >*/
/* Parameter adjustments */
a_dim1 = *nm;
a_offset = 1 + a_dim1;
a -= a_offset;
--int__;
/* Function Body */
la = *igh - 1;
/*< kp1 = low + 1 >*/
kp1 = *low + 1;
/*< if (la .lt. kp1) go to 200 >*/
if (la < kp1) {
goto L200;
}
/*< do 180 m = kp1, la >*/
i__1 = la;
for (m = kp1; m <= i__1; ++m) {
/*< mm1 = m - 1 >*/
mm1 = m - 1;
/*< x = 0.0d0 >*/
x = 0.;
/*< i = m >*/
i__ = m;
/*< do 100 j = m, igh >*/
i__2 = *igh;
for (j = m; j <= i__2; ++j) {
/*< if (dabs(a(j,mm1)) .le. dabs(x)) go to 100 >*/
if ((d__1 = a[j + mm1 * a_dim1], abs(d__1)) <= abs(x)) {
goto L100;
}
/*< x = a(j,mm1) >*/
x = a[j + mm1 * a_dim1];
/*< i = j >*/
i__ = j;
/*< 100 continue >*/
L100:
;
}
/*< int(m) = i >*/
int__[m] = i__;
/*< if (i .eq. m) go to 130 >*/
if (i__ == m) {
goto L130;
}
/* .......... interchange rows and columns of a .......... */
/*< do 110 j = mm1, n >*/
i__2 = *n;
for (j = mm1; j <= i__2; ++j) {
/*< y = a(i,j) >*/
y = a[i__ + j * a_dim1];
/*< a(i,j) = a(m,j) >*/
a[i__ + j * a_dim1] = a[m + j * a_dim1];
/*< a(m,j) = y >*/
a[m + j * a_dim1] = y;
/*< 110 continue >*/
/* L110: */
}
/*< do 120 j = 1, igh >*/
i__2 = *igh;
for (j = 1; j <= i__2; ++j) {
/*< y = a(j,i) >*/
y = a[j + i__ * a_dim1];
/*< a(j,i) = a(j,m) >*/
a[j + i__ * a_dim1] = a[j + m * a_dim1];
/*< a(j,m) = y >*/
a[j + m * a_dim1] = y;
/*< 120 continue >*/
/* L120: */
}
/* .......... end interchange .......... */
/*< 130 if (x .eq. 0.0d0) go to 180 >*/
L130:
if (x == 0.) {
goto L180;
}
/*< mp1 = m + 1 >*/
mp1 = m + 1;
/*< do 160 i = mp1, igh >*/
i__2 = *igh;
for (i__ = mp1; i__ <= i__2; ++i__) {
/*< y = a(i,mm1) >*/
y = a[i__ + mm1 * a_dim1];
/*< if (y .eq. 0.0d0) go to 160 >*/
if (y == 0.) {
goto L160;
}
/*< y = y / x >*/
y /= x;
/*< a(i,mm1) = y >*/
a[i__ + mm1 * a_dim1] = y;
/*< do 140 j = m, n >*/
i__3 = *n;
for (j = m; j <= i__3; ++j) {
/*< 140 a(i,j) = a(i,j) - y * a(m,j) >*/
/* L140: */
a[i__ + j * a_dim1] -= y * a[m + j * a_dim1];
}
/*< do 150 j = 1, igh >*/
i__3 = *igh;
for (j = 1; j <= i__3; ++j) {
/*< 150 a(j,m) = a(j,m) + y * a(j,i) >*/
/* L150: */
a[j + m * a_dim1] += y * a[j + i__ * a_dim1];
}
/*< 160 continue >*/
L160:
;
}
/*< 180 continue >*/
L180:
;
}
/*< 200 return >*/
L200:
return 0;
/*< end >*/
} /* elmhes_ */
#ifdef __cplusplus
}
#endif
|
