00001 /* sgeqrs.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 real c_b9 = 1.f; 00019 00020 /* Subroutine */ int sgeqrs_(integer *m, integer *n, integer *nrhs, real *a, 00021 integer *lda, real *tau, real *b, integer *ldb, real *work, integer * 00022 lwork, integer *info) 00023 { 00024 /* System generated locals */ 00025 integer a_dim1, a_offset, b_dim1, b_offset, i__1; 00026 00027 /* Local variables */ 00028 extern /* Subroutine */ int strsm_(char *, char *, char *, char *, 00029 integer *, integer *, real *, real *, integer *, real *, integer * 00030 ), xerbla_(char *, integer *), sormqr_(char *, char *, integer *, integer *, integer *, 00031 real *, integer *, real *, real *, integer *, real *, integer *, 00032 integer *); 00033 00034 00035 /* -- LAPACK routine (version 3.1) -- */ 00036 /* Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd.. */ 00037 /* November 2006 */ 00038 00039 /* .. Scalar Arguments .. */ 00040 /* .. */ 00041 /* .. Array Arguments .. */ 00042 /* .. */ 00043 00044 /* Purpose */ 00045 /* ======= */ 00046 00047 /* Solve the least squares problem */ 00048 /* min || A*X - B || */ 00049 /* using the QR factorization */ 00050 /* A = Q*R */ 00051 /* computed by SGEQRF. */ 00052 00053 /* Arguments */ 00054 /* ========= */ 00055 00056 /* M (input) INTEGER */ 00057 /* The number of rows of the matrix A. M >= 0. */ 00058 00059 /* N (input) INTEGER */ 00060 /* The number of columns of the matrix A. M >= N >= 0. */ 00061 00062 /* NRHS (input) INTEGER */ 00063 /* The number of columns of B. NRHS >= 0. */ 00064 00065 /* A (input) REAL array, dimension (LDA,N) */ 00066 /* Details of the QR factorization of the original matrix A as */ 00067 /* returned by SGEQRF. */ 00068 00069 /* LDA (input) INTEGER */ 00070 /* The leading dimension of the array A. LDA >= M. */ 00071 00072 /* TAU (input) REAL array, dimension (N) */ 00073 /* Details of the orthogonal matrix Q. */ 00074 00075 /* B (input/output) REAL array, dimension (LDB,NRHS) */ 00076 /* On entry, the m-by-nrhs right hand side matrix B. */ 00077 /* On exit, the n-by-nrhs solution matrix X. */ 00078 00079 /* LDB (input) INTEGER */ 00080 /* The leading dimension of the array B. LDB >= M. */ 00081 00082 /* WORK (workspace) REAL array, dimension (LWORK) */ 00083 00084 /* LWORK (input) INTEGER */ 00085 /* The length of the array WORK. LWORK must be at least NRHS, */ 00086 /* and should be at least NRHS*NB, where NB is the block size */ 00087 /* for this environment. */ 00088 00089 /* INFO (output) INTEGER */ 00090 /* = 0: successful exit */ 00091 /* < 0: if INFO = -i, the i-th argument had an illegal value */ 00092 00093 /* ===================================================================== */ 00094 00095 /* .. Parameters .. */ 00096 /* .. */ 00097 /* .. External Subroutines .. */ 00098 /* .. */ 00099 /* .. Intrinsic Functions .. */ 00100 /* .. */ 00101 /* .. Executable Statements .. */ 00102 00103 /* Test the input arguments. */ 00104 00105 /* Parameter adjustments */ 00106 a_dim1 = *lda; 00107 a_offset = 1 + a_dim1; 00108 a -= a_offset; 00109 --tau; 00110 b_dim1 = *ldb; 00111 b_offset = 1 + b_dim1; 00112 b -= b_offset; 00113 --work; 00114 00115 /* Function Body */ 00116 *info = 0; 00117 if (*m < 0) { 00118 *info = -1; 00119 } else if (*n < 0 || *n > *m) { 00120 *info = -2; 00121 } else if (*nrhs < 0) { 00122 *info = -3; 00123 } else if (*lda < max(1,*m)) { 00124 *info = -5; 00125 } else if (*ldb < max(1,*m)) { 00126 *info = -8; 00127 } else if (*lwork < 1 || *lwork < *nrhs && *m > 0 && *n > 0) { 00128 *info = -10; 00129 } 00130 if (*info != 0) { 00131 i__1 = -(*info); 00132 xerbla_("SGEQRS", &i__1); 00133 return 0; 00134 } 00135 00136 /* Quick return if possible */ 00137 00138 if (*n == 0 || *nrhs == 0 || *m == 0) { 00139 return 0; 00140 } 00141 00142 /* B := Q' * B */ 00143 00144 sormqr_("Left", "Transpose", m, nrhs, n, &a[a_offset], lda, &tau[1], &b[ 00145 b_offset], ldb, &work[1], lwork, info); 00146 00147 /* Solve R*X = B(1:n,:) */ 00148 00149 strsm_("Left", "Upper", "No transpose", "Non-unit", n, nrhs, &c_b9, &a[ 00150 a_offset], lda, &b[b_offset], ldb); 00151 00152 return 0; 00153 00154 /* End of SGEQRS */ 00155 00156 } /* sgeqrs_ */