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161 lines
4.3 KiB
161 lines
4.3 KiB
/* sgeqr2.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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/* Subroutine */ int sgeqr2_(integer *m, integer *n, real *a, integer *lda, |
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real *tau, real *work, 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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/* Local variables */ |
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integer i__, k; |
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real aii; |
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extern /* Subroutine */ int slarf_(char *, integer *, integer *, real *, |
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integer *, real *, real *, integer *, real *), xerbla_( |
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char *, integer *), slarfp_(integer *, real *, real *, |
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integer *, real *); |
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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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/* SGEQR2 computes a QR factorization of a real m by n matrix A: */ |
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/* A = Q * R. */ |
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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 A. */ |
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/* On exit, the elements on and above the diagonal of the array */ |
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/* contain the min(m,n) by n upper trapezoidal matrix R (R is */ |
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/* upper triangular if m >= n); the elements below the diagonal, */ |
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/* with the array TAU, represent the orthogonal matrix Q as a */ |
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/* product of elementary reflectors (see Further Details). */ |
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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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/* TAU (output) REAL array, dimension (min(M,N)) */ |
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/* The scalar factors of the elementary reflectors (see Further */ |
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/* Details). */ |
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/* WORK (workspace) REAL array, dimension (N) */ |
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/* INFO (output) INTEGER */ |
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/* = 0: successful exit */ |
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/* < 0: if INFO = -i, the i-th argument had an illegal value */ |
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/* Further Details */ |
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/* =============== */ |
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/* The matrix Q is represented as a product of elementary reflectors */ |
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/* Q = H(1) H(2) . . . H(k), where k = min(m,n). */ |
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/* Each H(i) has the form */ |
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/* H(i) = I - tau * v * v' */ |
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/* where tau is a real scalar, and v is a real vector with */ |
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/* v(1:i-1) = 0 and v(i) = 1; v(i+1:m) is stored on exit in A(i+1:m,i), */ |
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/* and tau in TAU(i). */ |
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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 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 arguments */ |
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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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--tau; |
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--work; |
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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_("SGEQR2", &i__1); |
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return 0; |
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} |
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k = min(*m,*n); |
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i__1 = k; |
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for (i__ = 1; i__ <= i__1; ++i__) { |
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/* Generate elementary reflector H(i) to annihilate A(i+1:m,i) */ |
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i__2 = *m - i__ + 1; |
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/* Computing MIN */ |
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i__3 = i__ + 1; |
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slarfp_(&i__2, &a[i__ + i__ * a_dim1], &a[min(i__3, *m)+ i__ * a_dim1] |
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, &c__1, &tau[i__]); |
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if (i__ < *n) { |
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/* Apply H(i) to A(i:m,i+1:n) from the left */ |
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aii = a[i__ + i__ * a_dim1]; |
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a[i__ + i__ * a_dim1] = 1.f; |
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i__2 = *m - i__ + 1; |
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i__3 = *n - i__; |
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slarf_("Left", &i__2, &i__3, &a[i__ + i__ * a_dim1], &c__1, &tau[ |
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i__], &a[i__ + (i__ + 1) * a_dim1], lda, &work[1]); |
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a[i__ + i__ * a_dim1] = aii; |
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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 SGEQR2 */ |
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} /* sgeqr2_ */
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