|
1
2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 |
SUBROUTINE CPPTRS( UPLO, N, NRHS, AP, B, LDB, INFO )
* * -- LAPACK routine (version 3.3.1) -- * -- LAPACK is a software package provided by Univ. of Tennessee, -- * -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..-- * -- April 2011 -- * * .. Scalar Arguments .. CHARACTER UPLO INTEGER INFO, LDB, N, NRHS * .. * .. Array Arguments .. COMPLEX AP( * ), B( LDB, * ) * .. * * Purpose * ======= * * CPPTRS solves a system of linear equations A*X = B with a Hermitian * positive definite matrix A in packed storage using the Cholesky * factorization A = U**H*U or A = L*L**H computed by CPPTRF. * * Arguments * ========= * * UPLO (input) CHARACTER*1 * = 'U': Upper triangle of A is stored; * = 'L': Lower triangle of A is stored. * * N (input) INTEGER * The order of the matrix A. N >= 0. * * NRHS (input) INTEGER * The number of right hand sides, i.e., the number of columns * of the matrix B. NRHS >= 0. * * AP (input) COMPLEX array, dimension (N*(N+1)/2) * The triangular factor U or L from the Cholesky factorization * A = U**H*U or A = L*L**H, packed columnwise in a linear * array. The j-th column of U or L is stored in the array AP * as follows: * if UPLO = 'U', AP(i + (j-1)*j/2) = U(i,j) for 1<=i<=j; * if UPLO = 'L', AP(i + (j-1)*(2n-j)/2) = L(i,j) for j<=i<=n. * * B (input/output) COMPLEX array, dimension (LDB,NRHS) * On entry, the right hand side matrix B. * On exit, the solution matrix X. * * LDB (input) INTEGER * The leading dimension of the array B. LDB >= max(1,N). * * INFO (output) INTEGER * = 0: successful exit * < 0: if INFO = -i, the i-th argument had an illegal value * * ===================================================================== * * .. Local Scalars .. LOGICAL UPPER INTEGER I * .. * .. External Functions .. LOGICAL LSAME EXTERNAL LSAME * .. * .. External Subroutines .. EXTERNAL CTPSV, XERBLA * .. * .. Intrinsic Functions .. INTRINSIC MAX * .. * .. Executable Statements .. * * Test the input parameters. * INFO = 0 UPPER = LSAME( UPLO, 'U' ) IF( .NOT.UPPER .AND. .NOT.LSAME( UPLO, 'L' ) ) THEN INFO = -1 ELSE IF( N.LT.0 ) THEN INFO = -2 ELSE IF( NRHS.LT.0 ) THEN INFO = -3 ELSE IF( LDB.LT.MAX( 1, N ) ) THEN INFO = -6 END IF IF( INFO.NE.0 ) THEN CALL XERBLA( 'CPPTRS', -INFO ) RETURN END IF * * Quick return if possible * IF( N.EQ.0 .OR. NRHS.EQ.0 ) $ RETURN * IF( UPPER ) THEN * * Solve A*X = B where A = U**H * U. * DO 10 I = 1, NRHS * * Solve U**H *X = B, overwriting B with X. * CALL CTPSV( 'Upper', 'Conjugate transpose', 'Non-unit', N, $ AP, B( 1, I ), 1 ) * * Solve U*X = B, overwriting B with X. * CALL CTPSV( 'Upper', 'No transpose', 'Non-unit', N, AP, $ B( 1, I ), 1 ) 10 CONTINUE ELSE * * Solve A*X = B where A = L * L**H. * DO 20 I = 1, NRHS * * Solve L*Y = B, overwriting B with X. * CALL CTPSV( 'Lower', 'No transpose', 'Non-unit', N, AP, $ B( 1, I ), 1 ) * * Solve L**H *X = Y, overwriting B with X. * CALL CTPSV( 'Lower', 'Conjugate transpose', 'Non-unit', N, $ AP, B( 1, I ), 1 ) 20 CONTINUE END IF * RETURN * * End of CPPTRS * END |