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192 lines
5.1 KiB
192 lines
5.1 KiB
/* sgetf2.f -- translated by f2c (version 20061008). |
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You must link the resulting object file with libf2c: |
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on Microsoft Windows system, link with libf2c.lib; |
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on Linux or Unix systems, link with .../path/to/libf2c.a -lm |
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or, if you install libf2c.a in a standard place, with -lf2c -lm |
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-- in that order, at the end of the command line, as in |
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cc *.o -lf2c -lm |
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Source for libf2c is in /netlib/f2c/libf2c.zip, e.g., |
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http://www.netlib.org/f2c/libf2c.zip |
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*/ |
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#include "clapack.h" |
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/* Table of constant values */ |
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static integer c__1 = 1; |
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static real c_b8 = -1.f; |
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/* Subroutine */ int sgetf2_(integer *m, integer *n, real *a, integer *lda, |
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integer *ipiv, integer *info) |
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{ |
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/* System generated locals */ |
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integer a_dim1, a_offset, i__1, i__2, i__3; |
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real r__1; |
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/* Local variables */ |
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integer i__, j, jp; |
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extern /* Subroutine */ int sger_(integer *, integer *, real *, real *, |
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integer *, real *, integer *, real *, integer *), sscal_(integer * |
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, real *, real *, integer *); |
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real sfmin; |
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extern /* Subroutine */ int sswap_(integer *, real *, integer *, real *, |
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integer *); |
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extern doublereal slamch_(char *); |
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extern /* Subroutine */ int xerbla_(char *, integer *); |
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extern integer isamax_(integer *, real *, integer *); |
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/* -- LAPACK routine (version 3.2) -- */ |
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/* Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd.. */ |
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/* November 2006 */ |
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/* .. Scalar Arguments .. */ |
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/* .. */ |
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/* .. Array Arguments .. */ |
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/* .. */ |
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/* Purpose */ |
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/* ======= */ |
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/* SGETF2 computes an LU factorization of a general m-by-n matrix A */ |
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/* using partial pivoting with row interchanges. */ |
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/* The factorization has the form */ |
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/* A = P * L * U */ |
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/* where P is a permutation matrix, L is lower triangular with unit */ |
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/* diagonal elements (lower trapezoidal if m > n), and U is upper */ |
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/* triangular (upper trapezoidal if m < n). */ |
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/* This is the right-looking Level 2 BLAS version of the algorithm. */ |
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/* Arguments */ |
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/* ========= */ |
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/* M (input) INTEGER */ |
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/* The number of rows of the matrix A. M >= 0. */ |
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/* N (input) INTEGER */ |
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/* The number of columns of the matrix A. N >= 0. */ |
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/* A (input/output) REAL array, dimension (LDA,N) */ |
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/* On entry, the m by n matrix to be factored. */ |
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/* On exit, the factors L and U from the factorization */ |
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/* A = P*L*U; the unit diagonal elements of L are not stored. */ |
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/* LDA (input) INTEGER */ |
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/* The leading dimension of the array A. LDA >= max(1,M). */ |
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/* IPIV (output) INTEGER array, dimension (min(M,N)) */ |
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/* The pivot indices; for 1 <= i <= min(M,N), row i of the */ |
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/* matrix was interchanged with row IPIV(i). */ |
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/* INFO (output) INTEGER */ |
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/* = 0: successful exit */ |
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/* < 0: if INFO = -k, the k-th argument had an illegal value */ |
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/* > 0: if INFO = k, U(k,k) is exactly zero. The factorization */ |
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/* has been completed, but the factor U is exactly */ |
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/* singular, and division by zero will occur if it is used */ |
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/* to solve a system of equations. */ |
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/* ===================================================================== */ |
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/* .. Parameters .. */ |
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/* .. */ |
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/* .. Local Scalars .. */ |
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/* .. */ |
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/* .. External Functions .. */ |
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/* .. */ |
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/* .. External Subroutines .. */ |
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/* .. */ |
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/* .. Intrinsic Functions .. */ |
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/* .. */ |
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/* .. Executable Statements .. */ |
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/* Test the input parameters. */ |
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/* Parameter adjustments */ |
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a_dim1 = *lda; |
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a_offset = 1 + a_dim1; |
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a -= a_offset; |
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--ipiv; |
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/* Function Body */ |
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*info = 0; |
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if (*m < 0) { |
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*info = -1; |
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} else if (*n < 0) { |
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*info = -2; |
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} else if (*lda < max(1,*m)) { |
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*info = -4; |
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} |
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if (*info != 0) { |
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i__1 = -(*info); |
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xerbla_("SGETF2", &i__1); |
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return 0; |
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} |
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/* Quick return if possible */ |
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if (*m == 0 || *n == 0) { |
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return 0; |
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} |
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/* Compute machine safe minimum */ |
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sfmin = slamch_("S"); |
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i__1 = min(*m,*n); |
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for (j = 1; j <= i__1; ++j) { |
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/* Find pivot and test for singularity. */ |
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i__2 = *m - j + 1; |
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jp = j - 1 + isamax_(&i__2, &a[j + j * a_dim1], &c__1); |
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ipiv[j] = jp; |
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if (a[jp + j * a_dim1] != 0.f) { |
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/* Apply the interchange to columns 1:N. */ |
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if (jp != j) { |
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sswap_(n, &a[j + a_dim1], lda, &a[jp + a_dim1], lda); |
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} |
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/* Compute elements J+1:M of J-th column. */ |
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if (j < *m) { |
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if ((r__1 = a[j + j * a_dim1], dabs(r__1)) >= sfmin) { |
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i__2 = *m - j; |
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r__1 = 1.f / a[j + j * a_dim1]; |
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sscal_(&i__2, &r__1, &a[j + 1 + j * a_dim1], &c__1); |
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} else { |
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i__2 = *m - j; |
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for (i__ = 1; i__ <= i__2; ++i__) { |
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a[j + i__ + j * a_dim1] /= a[j + j * a_dim1]; |
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/* L20: */ |
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} |
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} |
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} |
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} else if (*info == 0) { |
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*info = j; |
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} |
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if (j < min(*m,*n)) { |
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/* Update trailing submatrix. */ |
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i__2 = *m - j; |
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i__3 = *n - j; |
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sger_(&i__2, &i__3, &c_b8, &a[j + 1 + j * a_dim1], &c__1, &a[j + ( |
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j + 1) * a_dim1], lda, &a[j + 1 + (j + 1) * a_dim1], lda); |
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} |
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/* L10: */ |
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} |
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return 0; |
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/* End of SGETF2 */ |
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} /* sgetf2_ */
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