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Diffstat (limited to 'SRC/zptsv.f')
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diff --git a/SRC/zptsv.f b/SRC/zptsv.f new file mode 100644 index 00000000..da0f7776 --- /dev/null +++ b/SRC/zptsv.f @@ -0,0 +1,100 @@ + SUBROUTINE ZPTSV( 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 D( * ) + COMPLEX*16 B( LDB, * ), E( * ) +* .. +* +* Purpose +* ======= +* +* ZPTSV computes the solution to a complex system of linear equations +* A*X = B, where A is an N-by-N Hermitian positive definite tridiagonal +* matrix, and X and B are N-by-NRHS matrices. +* +* A is factored as A = L*D*L**H, 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**H. +* +* E (input/output) COMPLEX*16 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**H factorization of +* A. E can also be regarded as the superdiagonal of the unit +* bidiagonal factor U from the U**H*D*U factorization of A. +* +* B (input/output) COMPLEX*16 array, dimension (LDB,N) +* 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 XERBLA, ZPTTRF, ZPTTRS +* .. +* .. 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( 'ZPTSV ', -INFO ) + RETURN + END IF +* +* Compute the L*D*L' (or U'*D*U) factorization of A. +* + CALL ZPTTRF( N, D, E, INFO ) + IF( INFO.EQ.0 ) THEN +* +* Solve the system A*X = B, overwriting B with X. +* + CALL ZPTTRS( 'Lower', N, NRHS, D, E, B, LDB, INFO ) + END IF + RETURN +* +* End of ZPTSV +* + END |