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annotate libcruft/lapack/sorgl2.f @ 9665:1dba57e9d08d

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use blas_trans_type for xgemm
author Jaroslav Hajek <highegg@gmail.com>
date Sat, 26 Sep 2009 10:41:07 +0200
parents 82be108cc558
children
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1 SUBROUTINE SORGL2( M, N, K, A, LDA, TAU, WORK, INFO )
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2 *
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3 * -- LAPACK routine (version 3.1) --
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4 * Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd..
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5 * November 2006
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6 *
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7 * .. Scalar Arguments ..
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8 INTEGER INFO, K, LDA, M, N
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9 * ..
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10 * .. Array Arguments ..
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11 REAL A( LDA, * ), TAU( * ), WORK( * )
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12 * ..
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13 *
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14 * Purpose
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15 * =======
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16 *
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17 * SORGL2 generates an m by n real matrix Q with orthonormal rows,
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18 * which is defined as the first m rows of a product of k elementary
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19 * reflectors of order n
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20 *
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21 * Q = H(k) . . . H(2) H(1)
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22 *
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23 * as returned by SGELQF.
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24 *
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25 * Arguments
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26 * =========
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27 *
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28 * M (input) INTEGER
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29 * The number of rows of the matrix Q. M >= 0.
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30 *
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31 * N (input) INTEGER
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32 * The number of columns of the matrix Q. N >= M.
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33 *
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34 * K (input) INTEGER
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35 * The number of elementary reflectors whose product defines the
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36 * matrix Q. M >= K >= 0.
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37 *
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38 * A (input/output) REAL array, dimension (LDA,N)
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39 * On entry, the i-th row must contain the vector which defines
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40 * the elementary reflector H(i), for i = 1,2,...,k, as returned
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41 * by SGELQF in the first k rows of its array argument A.
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42 * On exit, the m-by-n matrix Q.
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43 *
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44 * LDA (input) INTEGER
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45 * The first dimension of the array A. LDA >= max(1,M).
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46 *
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47 * TAU (input) REAL array, dimension (K)
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48 * TAU(i) must contain the scalar factor of the elementary
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49 * reflector H(i), as returned by SGELQF.
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50 *
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51 * WORK (workspace) REAL array, dimension (M)
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52 *
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53 * INFO (output) INTEGER
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54 * = 0: successful exit
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55 * < 0: if INFO = -i, the i-th argument has an illegal value
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56 *
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57 * =====================================================================
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58 *
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59 * .. Parameters ..
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60 REAL ONE, ZERO
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61 PARAMETER ( ONE = 1.0E+0, ZERO = 0.0E+0 )
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62 * ..
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63 * .. Local Scalars ..
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64 INTEGER I, J, L
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65 * ..
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66 * .. External Subroutines ..
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67 EXTERNAL SLARF, SSCAL, XERBLA
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68 * ..
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69 * .. Intrinsic Functions ..
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70 INTRINSIC MAX
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71 * ..
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72 * .. Executable Statements ..
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73 *
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74 * Test the input arguments
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75 *
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76 INFO = 0
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77 IF( M.LT.0 ) THEN
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78 INFO = -1
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79 ELSE IF( N.LT.M ) THEN
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80 INFO = -2
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81 ELSE IF( K.LT.0 .OR. K.GT.M ) THEN
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82 INFO = -3
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83 ELSE IF( LDA.LT.MAX( 1, M ) ) THEN
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84 INFO = -5
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85 END IF
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86 IF( INFO.NE.0 ) THEN
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87 CALL XERBLA( 'SORGL2', -INFO )
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88 RETURN
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89 END IF
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90 *
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91 * Quick return if possible
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92 *
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93 IF( M.LE.0 )
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94 $ RETURN
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95 *
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96 IF( K.LT.M ) THEN
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97 *
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98 * Initialise rows k+1:m to rows of the unit matrix
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99 *
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100 DO 20 J = 1, N
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101 DO 10 L = K + 1, M
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102 A( L, J ) = ZERO
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103 10 CONTINUE
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104 IF( J.GT.K .AND. J.LE.M )
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105 $ A( J, J ) = ONE
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106 20 CONTINUE
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107 END IF
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108 *
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109 DO 40 I = K, 1, -1
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110 *
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111 * Apply H(i) to A(i:m,i:n) from the right
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112 *
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113 IF( I.LT.N ) THEN
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114 IF( I.LT.M ) THEN
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115 A( I, I ) = ONE
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116 CALL SLARF( 'Right', M-I, N-I+1, A( I, I ), LDA,
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117 $ TAU( I ), A( I+1, I ), LDA, WORK )
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118 END IF
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119 CALL SSCAL( N-I, -TAU( I ), A( I, I+1 ), LDA )
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120 END IF
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121 A( I, I ) = ONE - TAU( I )
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122 *
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123 * Set A(i,1:i-1) to zero
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124 *
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125 DO 30 L = 1, I - 1
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126 A( I, L ) = ZERO
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127 30 CONTINUE
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128 40 CONTINUE
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129 RETURN
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130 *
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131 * End of SORGL2
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132 *
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133 END