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LAPACK 3.3.1
Linear Algebra PACKage
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LAPACK 3.3.1
Linear Algebra PACKage
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00001 SUBROUTINE CUPGTR( UPLO, N, AP, TAU, Q, LDQ, WORK, INFO ) 00002 * 00003 * -- LAPACK routine (version 3.2) -- 00004 * -- LAPACK is a software package provided by Univ. of Tennessee, -- 00005 * -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..-- 00006 * November 2006 00007 * 00008 * .. Scalar Arguments .. 00009 CHARACTER UPLO 00010 INTEGER INFO, LDQ, N 00011 * .. 00012 * .. Array Arguments .. 00013 COMPLEX AP( * ), Q( LDQ, * ), TAU( * ), WORK( * ) 00014 * .. 00015 * 00016 * Purpose 00017 * ======= 00018 * 00019 * CUPGTR generates a complex unitary matrix Q which is defined as the 00020 * product of n-1 elementary reflectors H(i) of order n, as returned by 00021 * CHPTRD using packed storage: 00022 * 00023 * if UPLO = 'U', Q = H(n-1) . . . H(2) H(1), 00024 * 00025 * if UPLO = 'L', Q = H(1) H(2) . . . H(n-1). 00026 * 00027 * Arguments 00028 * ========= 00029 * 00030 * UPLO (input) CHARACTER*1 00031 * = 'U': Upper triangular packed storage used in previous 00032 * call to CHPTRD; 00033 * = 'L': Lower triangular packed storage used in previous 00034 * call to CHPTRD. 00035 * 00036 * N (input) INTEGER 00037 * The order of the matrix Q. N >= 0. 00038 * 00039 * AP (input) COMPLEX array, dimension (N*(N+1)/2) 00040 * The vectors which define the elementary reflectors, as 00041 * returned by CHPTRD. 00042 * 00043 * TAU (input) COMPLEX array, dimension (N-1) 00044 * TAU(i) must contain the scalar factor of the elementary 00045 * reflector H(i), as returned by CHPTRD. 00046 * 00047 * Q (output) COMPLEX array, dimension (LDQ,N) 00048 * The N-by-N unitary matrix Q. 00049 * 00050 * LDQ (input) INTEGER 00051 * The leading dimension of the array Q. LDQ >= max(1,N). 00052 * 00053 * WORK (workspace) COMPLEX array, dimension (N-1) 00054 * 00055 * INFO (output) INTEGER 00056 * = 0: successful exit 00057 * < 0: if INFO = -i, the i-th argument had an illegal value 00058 * 00059 * ===================================================================== 00060 * 00061 * .. Parameters .. 00062 COMPLEX CZERO, CONE 00063 PARAMETER ( CZERO = ( 0.0E+0, 0.0E+0 ), 00064 $ CONE = ( 1.0E+0, 0.0E+0 ) ) 00065 * .. 00066 * .. Local Scalars .. 00067 LOGICAL UPPER 00068 INTEGER I, IINFO, IJ, J 00069 * .. 00070 * .. External Functions .. 00071 LOGICAL LSAME 00072 EXTERNAL LSAME 00073 * .. 00074 * .. External Subroutines .. 00075 EXTERNAL CUNG2L, CUNG2R, XERBLA 00076 * .. 00077 * .. Intrinsic Functions .. 00078 INTRINSIC MAX 00079 * .. 00080 * .. Executable Statements .. 00081 * 00082 * Test the input arguments 00083 * 00084 INFO = 0 00085 UPPER = LSAME( UPLO, 'U' ) 00086 IF( .NOT.UPPER .AND. .NOT.LSAME( UPLO, 'L' ) ) THEN 00087 INFO = -1 00088 ELSE IF( N.LT.0 ) THEN 00089 INFO = -2 00090 ELSE IF( LDQ.LT.MAX( 1, N ) ) THEN 00091 INFO = -6 00092 END IF 00093 IF( INFO.NE.0 ) THEN 00094 CALL XERBLA( 'CUPGTR', -INFO ) 00095 RETURN 00096 END IF 00097 * 00098 * Quick return if possible 00099 * 00100 IF( N.EQ.0 ) 00101 $ RETURN 00102 * 00103 IF( UPPER ) THEN 00104 * 00105 * Q was determined by a call to CHPTRD with UPLO = 'U' 00106 * 00107 * Unpack the vectors which define the elementary reflectors and 00108 * set the last row and column of Q equal to those of the unit 00109 * matrix 00110 * 00111 IJ = 2 00112 DO 20 J = 1, N - 1 00113 DO 10 I = 1, J - 1 00114 Q( I, J ) = AP( IJ ) 00115 IJ = IJ + 1 00116 10 CONTINUE 00117 IJ = IJ + 2 00118 Q( N, J ) = CZERO 00119 20 CONTINUE 00120 DO 30 I = 1, N - 1 00121 Q( I, N ) = CZERO 00122 30 CONTINUE 00123 Q( N, N ) = CONE 00124 * 00125 * Generate Q(1:n-1,1:n-1) 00126 * 00127 CALL CUNG2L( N-1, N-1, N-1, Q, LDQ, TAU, WORK, IINFO ) 00128 * 00129 ELSE 00130 * 00131 * Q was determined by a call to CHPTRD with UPLO = 'L'. 00132 * 00133 * Unpack the vectors which define the elementary reflectors and 00134 * set the first row and column of Q equal to those of the unit 00135 * matrix 00136 * 00137 Q( 1, 1 ) = CONE 00138 DO 40 I = 2, N 00139 Q( I, 1 ) = CZERO 00140 40 CONTINUE 00141 IJ = 3 00142 DO 60 J = 2, N 00143 Q( 1, J ) = CZERO 00144 DO 50 I = J + 1, N 00145 Q( I, J ) = AP( IJ ) 00146 IJ = IJ + 1 00147 50 CONTINUE 00148 IJ = IJ + 2 00149 60 CONTINUE 00150 IF( N.GT.1 ) THEN 00151 * 00152 * Generate Q(2:n,2:n) 00153 * 00154 CALL CUNG2R( N-1, N-1, N-1, Q( 2, 2 ), LDQ, TAU, WORK, 00155 $ IINFO ) 00156 END IF 00157 END IF 00158 RETURN 00159 * 00160 * End of CUPGTR 00161 * 00162 END
1.7.3 
