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annotate libcruft/lapack/clauu2.f @ 8489:e76b92c7f779

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[docs] low cost => low-cost
author Brian Gough <bjg@gnu.org>
date Tue, 13 Jan 2009 00:26:46 -0500
parents 82be108cc558
children
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1 SUBROUTINE CLAUU2( UPLO, N, A, LDA, INFO )
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2 *
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3 * -- LAPACK auxiliary 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 CHARACTER UPLO
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9 INTEGER INFO, LDA, N
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10 * ..
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11 * .. Array Arguments ..
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12 COMPLEX A( LDA, * )
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13 * ..
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14 *
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15 * Purpose
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16 * =======
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17 *
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18 * CLAUU2 computes the product U * U' or L' * L, where the triangular
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19 * factor U or L is stored in the upper or lower triangular part of
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20 * the array A.
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21 *
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22 * If UPLO = 'U' or 'u' then the upper triangle of the result is stored,
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23 * overwriting the factor U in A.
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24 * If UPLO = 'L' or 'l' then the lower triangle of the result is stored,
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25 * overwriting the factor L in A.
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26 *
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27 * This is the unblocked form of the algorithm, calling Level 2 BLAS.
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28 *
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29 * Arguments
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30 * =========
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31 *
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32 * UPLO (input) CHARACTER*1
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33 * Specifies whether the triangular factor stored in the array A
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34 * is upper or lower triangular:
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35 * = 'U': Upper triangular
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36 * = 'L': Lower triangular
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37 *
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38 * N (input) INTEGER
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39 * The order of the triangular factor U or L. N >= 0.
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40 *
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41 * A (input/output) COMPLEX array, dimension (LDA,N)
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42 * On entry, the triangular factor U or L.
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43 * On exit, if UPLO = 'U', the upper triangle of A is
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44 * overwritten with the upper triangle of the product U * U';
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45 * if UPLO = 'L', the lower triangle of A is overwritten with
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46 * the lower triangle of the product L' * L.
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47 *
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48 * LDA (input) INTEGER
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49 * The leading dimension of the array A. LDA >= max(1,N).
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50 *
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51 * INFO (output) INTEGER
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52 * = 0: successful exit
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53 * < 0: if INFO = -k, the k-th argument had an illegal value
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54 *
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55 * =====================================================================
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56 *
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57 * .. Parameters ..
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58 COMPLEX ONE
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59 PARAMETER ( ONE = ( 1.0E+0, 0.0E+0 ) )
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60 * ..
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61 * .. Local Scalars ..
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62 LOGICAL UPPER
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63 INTEGER I
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64 REAL AII
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65 * ..
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66 * .. External Functions ..
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67 LOGICAL LSAME
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68 COMPLEX CDOTC
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69 EXTERNAL LSAME, CDOTC
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70 * ..
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71 * .. External Subroutines ..
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72 EXTERNAL CGEMV, CLACGV, CSSCAL, XERBLA
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73 * ..
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74 * .. Intrinsic Functions ..
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75 INTRINSIC CMPLX, MAX, REAL
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76 * ..
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77 * .. Executable Statements ..
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78 *
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79 * Test the input parameters.
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80 *
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81 INFO = 0
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82 UPPER = LSAME( UPLO, 'U' )
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83 IF( .NOT.UPPER .AND. .NOT.LSAME( UPLO, 'L' ) ) THEN
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84 INFO = -1
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85 ELSE IF( N.LT.0 ) THEN
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86 INFO = -2
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87 ELSE IF( LDA.LT.MAX( 1, N ) ) THEN
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88 INFO = -4
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89 END IF
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90 IF( INFO.NE.0 ) THEN
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91 CALL XERBLA( 'CLAUU2', -INFO )
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92 RETURN
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93 END IF
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94 *
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95 * Quick return if possible
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96 *
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97 IF( N.EQ.0 )
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98 $ RETURN
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99 *
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100 IF( UPPER ) THEN
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101 *
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102 * Compute the product U * U'.
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103 *
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104 DO 10 I = 1, N
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105 AII = A( I, I )
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106 IF( I.LT.N ) THEN
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107 A( I, I ) = AII*AII + REAL( CDOTC( N-I, A( I, I+1 ), LDA,
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108 $ A( I, I+1 ), LDA ) )
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109 CALL CLACGV( N-I, A( I, I+1 ), LDA )
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110 CALL CGEMV( 'No transpose', I-1, N-I, ONE, A( 1, I+1 ),
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111 $ LDA, A( I, I+1 ), LDA, CMPLX( AII ),
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112 $ A( 1, I ), 1 )
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113 CALL CLACGV( N-I, A( I, I+1 ), LDA )
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114 ELSE
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115 CALL CSSCAL( I, AII, A( 1, I ), 1 )
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116 END IF
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117 10 CONTINUE
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118 *
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119 ELSE
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120 *
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121 * Compute the product L' * L.
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122 *
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123 DO 20 I = 1, N
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124 AII = A( I, I )
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125 IF( I.LT.N ) THEN
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126 A( I, I ) = AII*AII + REAL( CDOTC( N-I, A( I+1, I ), 1,
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127 $ A( I+1, I ), 1 ) )
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128 CALL CLACGV( I-1, A( I, 1 ), LDA )
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129 CALL CGEMV( 'Conjugate transpose', N-I, I-1, ONE,
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130 $ A( I+1, 1 ), LDA, A( I+1, I ), 1,
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131 $ CMPLX( AII ), A( I, 1 ), LDA )
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132 CALL CLACGV( I-1, A( I, 1 ), LDA )
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133 ELSE
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134 CALL CSSCAL( I, AII, A( I, 1 ), LDA )
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135 END IF
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136 20 CONTINUE
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137 END IF
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138 *
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139 RETURN
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140 *
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141 * End of CLAUU2
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142 *
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143 END