sorg2r.c
Go to the documentation of this file.
00001 /* sorg2r.f -- translated by f2c (version 20061008).
00002    You must link the resulting object file with libf2c:
00003         on Microsoft Windows system, link with libf2c.lib;
00004         on Linux or Unix systems, link with .../path/to/libf2c.a -lm
00005         or, if you install libf2c.a in a standard place, with -lf2c -lm
00006         -- in that order, at the end of the command line, as in
00007                 cc *.o -lf2c -lm
00008         Source for libf2c is in /netlib/f2c/libf2c.zip, e.g.,
00009 
00010                 http://www.netlib.org/f2c/libf2c.zip
00011 */
00012 
00013 #include "f2c.h"
00014 #include "blaswrap.h"
00015 
00016 /* Table of constant values */
00017 
00018 static integer c__1 = 1;
00019 
00020 /* Subroutine */ int sorg2r_(integer *m, integer *n, integer *k, real *a, 
00021         integer *lda, real *tau, real *work, integer *info)
00022 {
00023     /* System generated locals */
00024     integer a_dim1, a_offset, i__1, i__2;
00025     real r__1;
00026 
00027     /* Local variables */
00028     integer i__, j, l;
00029     extern /* Subroutine */ int sscal_(integer *, real *, real *, integer *), 
00030             slarf_(char *, integer *, integer *, real *, integer *, real *, 
00031             real *, integer *, real *), xerbla_(char *, integer *);
00032 
00033 
00034 /*  -- LAPACK routine (version 3.2) -- */
00035 /*     Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd.. */
00036 /*     November 2006 */
00037 
00038 /*     .. Scalar Arguments .. */
00039 /*     .. */
00040 /*     .. Array Arguments .. */
00041 /*     .. */
00042 
00043 /*  Purpose */
00044 /*  ======= */
00045 
00046 /*  SORG2R generates an m by n real matrix Q with orthonormal columns, */
00047 /*  which is defined as the first n columns of a product of k elementary */
00048 /*  reflectors of order m */
00049 
00050 /*        Q  =  H(1) H(2) . . . H(k) */
00051 
00052 /*  as returned by SGEQRF. */
00053 
00054 /*  Arguments */
00055 /*  ========= */
00056 
00057 /*  M       (input) INTEGER */
00058 /*          The number of rows of the matrix Q. M >= 0. */
00059 
00060 /*  N       (input) INTEGER */
00061 /*          The number of columns of the matrix Q. M >= N >= 0. */
00062 
00063 /*  K       (input) INTEGER */
00064 /*          The number of elementary reflectors whose product defines the */
00065 /*          matrix Q. N >= K >= 0. */
00066 
00067 /*  A       (input/output) REAL array, dimension (LDA,N) */
00068 /*          On entry, the i-th column must contain the vector which */
00069 /*          defines the elementary reflector H(i), for i = 1,2,...,k, as */
00070 /*          returned by SGEQRF in the first k columns of its array */
00071 /*          argument A. */
00072 /*          On exit, the m-by-n matrix Q. */
00073 
00074 /*  LDA     (input) INTEGER */
00075 /*          The first dimension of the array A. LDA >= max(1,M). */
00076 
00077 /*  TAU     (input) REAL array, dimension (K) */
00078 /*          TAU(i) must contain the scalar factor of the elementary */
00079 /*          reflector H(i), as returned by SGEQRF. */
00080 
00081 /*  WORK    (workspace) REAL array, dimension (N) */
00082 
00083 /*  INFO    (output) INTEGER */
00084 /*          = 0: successful exit */
00085 /*          < 0: if INFO = -i, the i-th argument has an illegal value */
00086 
00087 /*  ===================================================================== */
00088 
00089 /*     .. Parameters .. */
00090 /*     .. */
00091 /*     .. Local Scalars .. */
00092 /*     .. */
00093 /*     .. External Subroutines .. */
00094 /*     .. */
00095 /*     .. Intrinsic Functions .. */
00096 /*     .. */
00097 /*     .. Executable Statements .. */
00098 
00099 /*     Test the input arguments */
00100 
00101     /* Parameter adjustments */
00102     a_dim1 = *lda;
00103     a_offset = 1 + a_dim1;
00104     a -= a_offset;
00105     --tau;
00106     --work;
00107 
00108     /* Function Body */
00109     *info = 0;
00110     if (*m < 0) {
00111         *info = -1;
00112     } else if (*n < 0 || *n > *m) {
00113         *info = -2;
00114     } else if (*k < 0 || *k > *n) {
00115         *info = -3;
00116     } else if (*lda < max(1,*m)) {
00117         *info = -5;
00118     }
00119     if (*info != 0) {
00120         i__1 = -(*info);
00121         xerbla_("SORG2R", &i__1);
00122         return 0;
00123     }
00124 
00125 /*     Quick return if possible */
00126 
00127     if (*n <= 0) {
00128         return 0;
00129     }
00130 
00131 /*     Initialise columns k+1:n to columns of the unit matrix */
00132 
00133     i__1 = *n;
00134     for (j = *k + 1; j <= i__1; ++j) {
00135         i__2 = *m;
00136         for (l = 1; l <= i__2; ++l) {
00137             a[l + j * a_dim1] = 0.f;
00138 /* L10: */
00139         }
00140         a[j + j * a_dim1] = 1.f;
00141 /* L20: */
00142     }
00143 
00144     for (i__ = *k; i__ >= 1; --i__) {
00145 
00146 /*        Apply H(i) to A(i:m,i:n) from the left */
00147 
00148         if (i__ < *n) {
00149             a[i__ + i__ * a_dim1] = 1.f;
00150             i__1 = *m - i__ + 1;
00151             i__2 = *n - i__;
00152             slarf_("Left", &i__1, &i__2, &a[i__ + i__ * a_dim1], &c__1, &tau[
00153                     i__], &a[i__ + (i__ + 1) * a_dim1], lda, &work[1]);
00154         }
00155         if (i__ < *m) {
00156             i__1 = *m - i__;
00157             r__1 = -tau[i__];
00158             sscal_(&i__1, &r__1, &a[i__ + 1 + i__ * a_dim1], &c__1);
00159         }
00160         a[i__ + i__ * a_dim1] = 1.f - tau[i__];
00161 
00162 /*        Set A(1:i-1,i) to zero */
00163 
00164         i__1 = i__ - 1;
00165         for (l = 1; l <= i__1; ++l) {
00166             a[l + i__ * a_dim1] = 0.f;
00167 /* L30: */
00168         }
00169 /* L40: */
00170     }
00171     return 0;
00172 
00173 /*     End of SORG2R */
00174 
00175 } /* sorg2r_ */


swiftnav
Author(s):
autogenerated on Sat Jun 8 2019 18:56:12