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author | jason <jason@8a072113-8704-0410-8d35-dd094bca7971> | 2008-10-28 01:38:50 +0000 |
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committer | jason <jason@8a072113-8704-0410-8d35-dd094bca7971> | 2008-10-28 01:38:50 +0000 |
commit | baba851215b44ac3b60b9248eb02bcce7eb76247 (patch) | |
tree | 8c0f5c006875532a30d4409f5e94b0f310ff00a7 /SRC/zpptrs.f | |
download | lapack-baba851215b44ac3b60b9248eb02bcce7eb76247.tar.gz lapack-baba851215b44ac3b60b9248eb02bcce7eb76247.tar.bz2 lapack-baba851215b44ac3b60b9248eb02bcce7eb76247.zip |
Move LAPACK trunk into position.
Diffstat (limited to 'SRC/zpptrs.f')
-rw-r--r-- | SRC/zpptrs.f | 134 |
1 files changed, 134 insertions, 0 deletions
diff --git a/SRC/zpptrs.f b/SRC/zpptrs.f new file mode 100644 index 00000000..0a9b9266 --- /dev/null +++ b/SRC/zpptrs.f @@ -0,0 +1,134 @@ + SUBROUTINE ZPPTRS( UPLO, N, NRHS, AP, B, LDB, INFO ) +* +* -- LAPACK routine (version 3.1) -- +* Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd.. +* November 2006 +* +* .. Scalar Arguments .. + CHARACTER UPLO + INTEGER INFO, LDB, N, NRHS +* .. +* .. Array Arguments .. + COMPLEX*16 AP( * ), B( LDB, * ) +* .. +* +* Purpose +* ======= +* +* ZPPTRS 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 ZPPTRF. +* +* 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*16 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*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 I +* .. +* .. External Functions .. + LOGICAL LSAME + EXTERNAL LSAME +* .. +* .. External Subroutines .. + EXTERNAL XERBLA, ZTPSV +* .. +* .. 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( 'ZPPTRS', -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 I = 1, NRHS +* +* Solve U'*X = B, overwriting B with X. +* + CALL ZTPSV( 'Upper', 'Conjugate transpose', 'Non-unit', N, + $ AP, B( 1, I ), 1 ) +* +* Solve U*X = B, overwriting B with X. +* + CALL ZTPSV( 'Upper', 'No transpose', 'Non-unit', N, AP, + $ B( 1, I ), 1 ) + 10 CONTINUE + ELSE +* +* Solve A*X = B where A = L*L'. +* + DO 20 I = 1, NRHS +* +* Solve L*Y = B, overwriting B with X. +* + CALL ZTPSV( 'Lower', 'No transpose', 'Non-unit', N, AP, + $ B( 1, I ), 1 ) +* +* Solve L'*X = Y, overwriting B with X. +* + CALL ZTPSV( 'Lower', 'Conjugate transpose', 'Non-unit', N, + $ AP, B( 1, I ), 1 ) + 20 CONTINUE + END IF +* + RETURN +* +* End of ZPPTRS +* + END |