Annotation of rpl/lapack/lapack/zpotrs.f, revision 1.1
1.1 ! bertrand 1: SUBROUTINE ZPOTRS( UPLO, N, NRHS, A, LDA, B, LDB, INFO )
! 2: *
! 3: * -- LAPACK routine (version 3.2) --
! 4: * -- LAPACK is a software package provided by Univ. of Tennessee, --
! 5: * -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
! 6: * November 2006
! 7: *
! 8: * .. Scalar Arguments ..
! 9: CHARACTER UPLO
! 10: INTEGER INFO, LDA, LDB, N, NRHS
! 11: * ..
! 12: * .. Array Arguments ..
! 13: COMPLEX*16 A( LDA, * ), B( LDB, * )
! 14: * ..
! 15: *
! 16: * Purpose
! 17: * =======
! 18: *
! 19: * ZPOTRS solves a system of linear equations A*X = B with a Hermitian
! 20: * positive definite matrix A using the Cholesky factorization
! 21: * A = U**H*U or A = L*L**H computed by ZPOTRF.
! 22: *
! 23: * Arguments
! 24: * =========
! 25: *
! 26: * UPLO (input) CHARACTER*1
! 27: * = 'U': Upper triangle of A is stored;
! 28: * = 'L': Lower triangle of A is stored.
! 29: *
! 30: * N (input) INTEGER
! 31: * The order of the matrix A. N >= 0.
! 32: *
! 33: * NRHS (input) INTEGER
! 34: * The number of right hand sides, i.e., the number of columns
! 35: * of the matrix B. NRHS >= 0.
! 36: *
! 37: * A (input) COMPLEX*16 array, dimension (LDA,N)
! 38: * The triangular factor U or L from the Cholesky factorization
! 39: * A = U**H*U or A = L*L**H, as computed by ZPOTRF.
! 40: *
! 41: * LDA (input) INTEGER
! 42: * The leading dimension of the array A. LDA >= max(1,N).
! 43: *
! 44: * B (input/output) COMPLEX*16 array, dimension (LDB,NRHS)
! 45: * On entry, the right hand side matrix B.
! 46: * On exit, the solution matrix X.
! 47: *
! 48: * LDB (input) INTEGER
! 49: * The leading dimension of the array B. LDB >= max(1,N).
! 50: *
! 51: * INFO (output) INTEGER
! 52: * = 0: successful exit
! 53: * < 0: if INFO = -i, the i-th argument had an illegal value
! 54: *
! 55: * =====================================================================
! 56: *
! 57: * .. Parameters ..
! 58: COMPLEX*16 ONE
! 59: PARAMETER ( ONE = ( 1.0D+0, 0.0D+0 ) )
! 60: * ..
! 61: * .. Local Scalars ..
! 62: LOGICAL UPPER
! 63: * ..
! 64: * .. External Functions ..
! 65: LOGICAL LSAME
! 66: EXTERNAL LSAME
! 67: * ..
! 68: * .. External Subroutines ..
! 69: EXTERNAL XERBLA, ZTRSM
! 70: * ..
! 71: * .. Intrinsic Functions ..
! 72: INTRINSIC MAX
! 73: * ..
! 74: * .. Executable Statements ..
! 75: *
! 76: * Test the input parameters.
! 77: *
! 78: INFO = 0
! 79: UPPER = LSAME( UPLO, 'U' )
! 80: IF( .NOT.UPPER .AND. .NOT.LSAME( UPLO, 'L' ) ) THEN
! 81: INFO = -1
! 82: ELSE IF( N.LT.0 ) THEN
! 83: INFO = -2
! 84: ELSE IF( NRHS.LT.0 ) THEN
! 85: INFO = -3
! 86: ELSE IF( LDA.LT.MAX( 1, N ) ) THEN
! 87: INFO = -5
! 88: ELSE IF( LDB.LT.MAX( 1, N ) ) THEN
! 89: INFO = -7
! 90: END IF
! 91: IF( INFO.NE.0 ) THEN
! 92: CALL XERBLA( 'ZPOTRS', -INFO )
! 93: RETURN
! 94: END IF
! 95: *
! 96: * Quick return if possible
! 97: *
! 98: IF( N.EQ.0 .OR. NRHS.EQ.0 )
! 99: $ RETURN
! 100: *
! 101: IF( UPPER ) THEN
! 102: *
! 103: * Solve A*X = B where A = U'*U.
! 104: *
! 105: * Solve U'*X = B, overwriting B with X.
! 106: *
! 107: CALL ZTRSM( 'Left', 'Upper', 'Conjugate transpose', 'Non-unit',
! 108: $ N, NRHS, ONE, A, LDA, B, LDB )
! 109: *
! 110: * Solve U*X = B, overwriting B with X.
! 111: *
! 112: CALL ZTRSM( 'Left', 'Upper', 'No transpose', 'Non-unit', N,
! 113: $ NRHS, ONE, A, LDA, B, LDB )
! 114: ELSE
! 115: *
! 116: * Solve A*X = B where A = L*L'.
! 117: *
! 118: * Solve L*X = B, overwriting B with X.
! 119: *
! 120: CALL ZTRSM( 'Left', 'Lower', 'No transpose', 'Non-unit', N,
! 121: $ NRHS, ONE, A, LDA, B, LDB )
! 122: *
! 123: * Solve L'*X = B, overwriting B with X.
! 124: *
! 125: CALL ZTRSM( 'Left', 'Lower', 'Conjugate transpose', 'Non-unit',
! 126: $ N, NRHS, ONE, A, LDA, B, LDB )
! 127: END IF
! 128: *
! 129: RETURN
! 130: *
! 131: * End of ZPOTRS
! 132: *
! 133: END
CVSweb interface <joel.bertrand@systella.fr>