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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/dptsv.f | |
download | lapack-baba851215b44ac3b60b9248eb02bcce7eb76247.tar.gz lapack-baba851215b44ac3b60b9248eb02bcce7eb76247.tar.bz2 lapack-baba851215b44ac3b60b9248eb02bcce7eb76247.zip |
Move LAPACK trunk into position.
Diffstat (limited to 'SRC/dptsv.f')
-rw-r--r-- | SRC/dptsv.f | 99 |
1 files changed, 99 insertions, 0 deletions
diff --git a/SRC/dptsv.f b/SRC/dptsv.f new file mode 100644 index 00000000..dd5f0bed --- /dev/null +++ b/SRC/dptsv.f @@ -0,0 +1,99 @@ + SUBROUTINE DPTSV( N, NRHS, D, E, B, LDB, INFO ) +* +* -- LAPACK routine (version 3.1) -- +* Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd.. +* November 2006 +* +* .. Scalar Arguments .. + INTEGER INFO, LDB, N, NRHS +* .. +* .. Array Arguments .. + DOUBLE PRECISION B( LDB, * ), D( * ), E( * ) +* .. +* +* Purpose +* ======= +* +* DPTSV computes the solution to a real system of linear equations +* A*X = B, where A is an N-by-N symmetric positive definite tridiagonal +* matrix, and X and B are N-by-NRHS matrices. +* +* A is factored as A = L*D*L**T, and the factored form of A is then +* used to solve the system of equations. +* +* Arguments +* ========= +* +* 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. +* +* D (input/output) DOUBLE PRECISION array, dimension (N) +* On entry, the n diagonal elements of the tridiagonal matrix +* A. On exit, the n diagonal elements of the diagonal matrix +* D from the factorization A = L*D*L**T. +* +* E (input/output) DOUBLE PRECISION array, dimension (N-1) +* On entry, the (n-1) subdiagonal elements of the tridiagonal +* matrix A. On exit, the (n-1) subdiagonal elements of the +* unit bidiagonal factor L from the L*D*L**T factorization of +* A. (E can also be regarded as the superdiagonal of the unit +* bidiagonal factor U from the U**T*D*U factorization of A.) +* +* B (input/output) DOUBLE PRECISION array, dimension (LDB,NRHS) +* On entry, the N-by-NRHS right hand side matrix B. +* On exit, if INFO = 0, the N-by-NRHS 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 +* > 0: if INFO = i, the leading minor of order i is not +* positive definite, and the solution has not been +* computed. The factorization has not been completed +* unless i = N. +* +* ===================================================================== +* +* .. External Subroutines .. + EXTERNAL DPTTRF, DPTTRS, XERBLA +* .. +* .. Intrinsic Functions .. + INTRINSIC MAX +* .. +* .. Executable Statements .. +* +* Test the input parameters. +* + INFO = 0 + IF( N.LT.0 ) THEN + INFO = -1 + ELSE IF( NRHS.LT.0 ) THEN + INFO = -2 + ELSE IF( LDB.LT.MAX( 1, N ) ) THEN + INFO = -6 + END IF + IF( INFO.NE.0 ) THEN + CALL XERBLA( 'DPTSV ', -INFO ) + RETURN + END IF +* +* Compute the L*D*L' (or U'*D*U) factorization of A. +* + CALL DPTTRF( N, D, E, INFO ) + IF( INFO.EQ.0 ) THEN +* +* Solve the system A*X = B, overwriting B with X. +* + CALL DPTTRS( N, NRHS, D, E, B, LDB, INFO ) + END IF + RETURN +* +* End of DPTSV +* + END |