Mercurial > octave-nkf
diff libcruft/lapack/zpbtrs.f @ 5164:57077d0ddc8e
[project @ 2005-02-25 19:55:24 by jwe]
author | jwe |
---|---|
date | Fri, 25 Feb 2005 19:55:28 +0000 |
parents | |
children | 68db500cb558 |
line wrap: on
line diff
--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/libcruft/lapack/zpbtrs.f Fri Feb 25 19:55:28 2005 +0000 @@ -0,0 +1,146 @@ + SUBROUTINE ZPBTRS( UPLO, N, KD, NRHS, AB, LDAB, B, LDB, INFO ) +* +* -- LAPACK routine (version 3.0) -- +* Univ. of Tennessee, Univ. of California Berkeley, NAG Ltd., +* Courant Institute, Argonne National Lab, and Rice University +* September 30, 1994 +* +* .. Scalar Arguments .. + CHARACTER UPLO + INTEGER INFO, KD, LDAB, LDB, N, NRHS +* .. +* .. Array Arguments .. + COMPLEX*16 AB( LDAB, * ), B( LDB, * ) +* .. +* +* Purpose +* ======= +* +* ZPBTRS solves a system of linear equations A*X = B with a Hermitian +* positive definite band matrix A using the Cholesky factorization +* A = U**H*U or A = L*L**H computed by ZPBTRF. +* +* Arguments +* ========= +* +* UPLO (input) CHARACTER*1 +* = 'U': Upper triangular factor stored in AB; +* = 'L': Lower triangular factor stored in AB. +* +* N (input) INTEGER +* The order of the matrix A. N >= 0. +* +* KD (input) INTEGER +* The number of superdiagonals of the matrix A if UPLO = 'U', +* or the number of subdiagonals if UPLO = 'L'. KD >= 0. +* +* NRHS (input) INTEGER +* The number of right hand sides, i.e., the number of columns +* of the matrix B. NRHS >= 0. +* +* AB (input) COMPLEX*16 array, dimension (LDAB,N) +* The triangular factor U or L from the Cholesky factorization +* A = U**H*U or A = L*L**H of the band matrix A, stored in the +* first KD+1 rows of the array. The j-th column of U or L is +* stored in the j-th column of the array AB as follows: +* if UPLO ='U', AB(kd+1+i-j,j) = U(i,j) for max(1,j-kd)<=i<=j; +* if UPLO ='L', AB(1+i-j,j) = L(i,j) for j<=i<=min(n,j+kd). +* +* LDAB (input) INTEGER +* The leading dimension of the array AB. LDAB >= KD+1. +* +* B (input/output) COMPLEX*16 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 J +* .. +* .. External Functions .. + LOGICAL LSAME + EXTERNAL LSAME +* .. +* .. External Subroutines .. + EXTERNAL XERBLA, ZTBSV +* .. +* .. 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( KD.LT.0 ) THEN + INFO = -3 + ELSE IF( NRHS.LT.0 ) THEN + INFO = -4 + ELSE IF( LDAB.LT.KD+1 ) THEN + INFO = -6 + ELSE IF( LDB.LT.MAX( 1, N ) ) THEN + INFO = -8 + END IF + IF( INFO.NE.0 ) THEN + CALL XERBLA( 'ZPBTRS', -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'*U. +* + DO 10 J = 1, NRHS +* +* Solve U'*X = B, overwriting B with X. +* + CALL ZTBSV( 'Upper', 'Conjugate transpose', 'Non-unit', N, + $ KD, AB, LDAB, B( 1, J ), 1 ) +* +* Solve U*X = B, overwriting B with X. +* + CALL ZTBSV( 'Upper', 'No transpose', 'Non-unit', N, KD, AB, + $ LDAB, B( 1, J ), 1 ) + 10 CONTINUE + ELSE +* +* Solve A*X = B where A = L*L'. +* + DO 20 J = 1, NRHS +* +* Solve L*X = B, overwriting B with X. +* + CALL ZTBSV( 'Lower', 'No transpose', 'Non-unit', N, KD, AB, + $ LDAB, B( 1, J ), 1 ) +* +* Solve L'*X = B, overwriting B with X. +* + CALL ZTBSV( 'Lower', 'Conjugate transpose', 'Non-unit', N, + $ KD, AB, LDAB, B( 1, J ), 1 ) + 20 CONTINUE + END IF +* + RETURN +* +* End of ZPBTRS +* + END