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/* sgetc2.f -- translated by f2c (version 20061008).
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
*/
#include "f2c.h"
#include "blaswrap.h"
/* Table of constant values */
static integer c__1 = 1;
static real c_b10 = -1.f;
/* Subroutine */ int sgetc2_(integer *n, real *a, integer *lda, integer *ipiv,
integer *jpiv, integer *info)
{
/* System generated locals */
integer a_dim1, a_offset, i__1, i__2, i__3;
real r__1;
/* Local variables */
integer i__, j, ip, jp;
real eps;
integer ipv, jpv;
extern /* Subroutine */ int sger_(integer *, integer *, real *, real *,
integer *, real *, integer *, real *, integer *);
real smin, xmax;
extern /* Subroutine */ int sswap_(integer *, real *, integer *, real *,
integer *), slabad_(real *, real *);
extern doublereal slamch_(char *);
real bignum, smlnum;
/* -- LAPACK auxiliary routine (version 3.2) -- */
/* Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd.. */
/* November 2006 */
/* .. Scalar Arguments .. */
/* .. */
/* .. Array Arguments .. */
/* .. */
/* Purpose */
/* ======= */
/* SGETC2 computes an LU factorization with complete pivoting of the */
/* n-by-n matrix A. The factorization has the form A = P * L * U * Q, */
/* where P and Q are permutation matrices, L is lower triangular with */
/* unit diagonal elements and U is upper triangular. */
/* This is the Level 2 BLAS algorithm. */
/* Arguments */
/* ========= */
/* N (input) INTEGER */
/* The order of the matrix A. N >= 0. */
/* A (input/output) REAL array, dimension (LDA, N) */
/* On entry, the n-by-n matrix A to be factored. */
/* On exit, the factors L and U from the factorization */
/* A = P*L*U*Q; the unit diagonal elements of L are not stored. */
/* If U(k, k) appears to be less than SMIN, U(k, k) is given the */
/* value of SMIN, i.e., giving a nonsingular perturbed system. */
/* LDA (input) INTEGER */
/* The leading dimension of the array A. LDA >= max(1,N). */
/* IPIV (output) INTEGER array, dimension(N). */
/* The pivot indices; for 1 <= i <= N, row i of the */
/* matrix has been interchanged with row IPIV(i). */
/* JPIV (output) INTEGER array, dimension(N). */
/* The pivot indices; for 1 <= j <= N, column j of the */
/* matrix has been interchanged with column JPIV(j). */
/* INFO (output) INTEGER */
/* = 0: successful exit */
/* > 0: if INFO = k, U(k, k) is likely to produce owerflow if */
/* we try to solve for x in Ax = b. So U is perturbed to */
/* avoid the overflow. */
/* Further Details */
/* =============== */
/* Based on contributions by */
/* Bo Kagstrom and Peter Poromaa, Department of Computing Science, */
/* Umea University, S-901 87 Umea, Sweden. */
/* ===================================================================== */
/* .. Parameters .. */
/* .. */
/* .. Local Scalars .. */
/* .. */
/* .. External Subroutines .. */
/* .. */
/* .. External Functions .. */
/* .. */
/* .. Intrinsic Functions .. */
/* .. */
/* .. Executable Statements .. */
/* Set constants to control overflow */
/* Parameter adjustments */
a_dim1 = *lda;
a_offset = 1 + a_dim1;
a -= a_offset;
--ipiv;
--jpiv;
/* Function Body */
*info = 0;
eps = slamch_("P");
smlnum = slamch_("S") / eps;
bignum = 1.f / smlnum;
slabad_(&smlnum, &bignum);
/* Factorize A using complete pivoting. */
/* Set pivots less than SMIN to SMIN. */
i__1 = *n - 1;
for (i__ = 1; i__ <= i__1; ++i__) {
/* Find max element in matrix A */
xmax = 0.f;
i__2 = *n;
for (ip = i__; ip <= i__2; ++ip) {
i__3 = *n;
for (jp = i__; jp <= i__3; ++jp) {
if ((r__1 = a[ip + jp * a_dim1], dabs(r__1)) >= xmax) {
xmax = (r__1 = a[ip + jp * a_dim1], dabs(r__1));
ipv = ip;
jpv = jp;
}
/* L10: */
}
/* L20: */
}
if (i__ == 1) {
/* Computing MAX */
r__1 = eps * xmax;
smin = dmax(r__1,smlnum);
}
/* Swap rows */
if (ipv != i__) {
sswap_(n, &a[ipv + a_dim1], lda, &a[i__ + a_dim1], lda);
}
ipiv[i__] = ipv;
/* Swap columns */
if (jpv != i__) {
sswap_(n, &a[jpv * a_dim1 + 1], &c__1, &a[i__ * a_dim1 + 1], &
c__1);
}
jpiv[i__] = jpv;
/* Check for singularity */
if ((r__1 = a[i__ + i__ * a_dim1], dabs(r__1)) < smin) {
*info = i__;
a[i__ + i__ * a_dim1] = smin;
}
i__2 = *n;
for (j = i__ + 1; j <= i__2; ++j) {
a[j + i__ * a_dim1] /= a[i__ + i__ * a_dim1];
/* L30: */
}
i__2 = *n - i__;
i__3 = *n - i__;
sger_(&i__2, &i__3, &c_b10, &a[i__ + 1 + i__ * a_dim1], &c__1, &a[i__
+ (i__ + 1) * a_dim1], lda, &a[i__ + 1 + (i__ + 1) * a_dim1],
lda);
/* L40: */
}
if ((r__1 = a[*n + *n * a_dim1], dabs(r__1)) < smin) {
*info = *n;
a[*n + *n * a_dim1] = smin;
}
return 0;
/* End of SGETC2 */
} /* sgetc2_ */
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