julie
be91086043
Those are just cosmetic changes to update version number and various other minor change.
135 lines
4.1 KiB
FortranFixed
135 lines
4.1 KiB
FortranFixed
SUBROUTINE CPPSV( UPLO, N, NRHS, AP, B, LDB, INFO )
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*
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* -- LAPACK driver routine (version 3.2) --
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* -- LAPACK is a software package provided by Univ. of Tennessee, --
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* -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
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* November 2006
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*
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* .. Scalar Arguments ..
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CHARACTER UPLO
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INTEGER INFO, LDB, N, NRHS
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* ..
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* .. Array Arguments ..
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COMPLEX AP( * ), B( LDB, * )
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* ..
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*
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* Purpose
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* =======
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*
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* CPPSV computes the solution to a complex system of linear equations
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* A * X = B,
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* where A is an N-by-N Hermitian positive definite matrix stored in
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* packed format and X and B are N-by-NRHS matrices.
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*
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* The Cholesky decomposition is used to factor A as
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* A = U**H* U, if UPLO = 'U', or
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* A = L * L**H, if UPLO = 'L',
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* where U is an upper triangular matrix and L is a lower triangular
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* matrix. The factored form of A is then used to solve the system of
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* equations A * X = B.
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*
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* Arguments
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* =========
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*
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* UPLO (input) CHARACTER*1
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* = 'U': Upper triangle of A is stored;
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* = 'L': Lower triangle of A is stored.
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*
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* N (input) INTEGER
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* The number of linear equations, i.e., the order of the
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* matrix A. N >= 0.
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*
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* NRHS (input) INTEGER
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* The number of right hand sides, i.e., the number of columns
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* of the matrix B. NRHS >= 0.
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*
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* AP (input/output) COMPLEX array, dimension (N*(N+1)/2)
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* On entry, the upper or lower triangle of the Hermitian matrix
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* A, packed columnwise in a linear array. The j-th column of A
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* is stored in the array AP as follows:
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* if UPLO = 'U', AP(i + (j-1)*j/2) = A(i,j) for 1<=i<=j;
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* if UPLO = 'L', AP(i + (j-1)*(2n-j)/2) = A(i,j) for j<=i<=n.
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* See below for further details.
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*
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* On exit, if INFO = 0, the factor U or L from the Cholesky
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* factorization A = U**H*U or A = L*L**H, in the same storage
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* format as A.
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*
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* B (input/output) COMPLEX array, dimension (LDB,NRHS)
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* On entry, the N-by-NRHS right hand side matrix B.
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* On exit, if INFO = 0, the N-by-NRHS solution matrix X.
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*
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* LDB (input) INTEGER
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* The leading dimension of the array B. LDB >= max(1,N).
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*
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* INFO (output) INTEGER
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* = 0: successful exit
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* < 0: if INFO = -i, the i-th argument had an illegal value
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* > 0: if INFO = i, the leading minor of order i of A is not
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* positive definite, so the factorization could not be
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* completed, and the solution has not been computed.
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*
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* Further Details
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* ===============
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*
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* The packed storage scheme is illustrated by the following example
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* when N = 4, UPLO = 'U':
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*
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* Two-dimensional storage of the Hermitian matrix A:
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*
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* a11 a12 a13 a14
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* a22 a23 a24
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* a33 a34 (aij = conjg(aji))
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* a44
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*
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* Packed storage of the upper triangle of A:
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*
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* AP = [ a11, a12, a22, a13, a23, a33, a14, a24, a34, a44 ]
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*
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* =====================================================================
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*
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* .. External Functions ..
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LOGICAL LSAME
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EXTERNAL LSAME
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* ..
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* .. External Subroutines ..
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EXTERNAL CPPTRF, CPPTRS, XERBLA
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* ..
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* .. Intrinsic Functions ..
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INTRINSIC MAX
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* ..
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* .. Executable Statements ..
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*
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* Test the input parameters.
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*
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INFO = 0
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IF( .NOT.LSAME( UPLO, 'U' ) .AND. .NOT.LSAME( UPLO, 'L' ) ) THEN
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INFO = -1
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ELSE IF( N.LT.0 ) THEN
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INFO = -2
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ELSE IF( NRHS.LT.0 ) THEN
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INFO = -3
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ELSE IF( LDB.LT.MAX( 1, N ) ) THEN
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INFO = -6
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END IF
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IF( INFO.NE.0 ) THEN
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CALL XERBLA( 'CPPSV ', -INFO )
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RETURN
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END IF
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*
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* Compute the Cholesky factorization A = U'*U or A = L*L'.
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*
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CALL CPPTRF( UPLO, N, AP, INFO )
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IF( INFO.EQ.0 ) THEN
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*
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* Solve the system A*X = B, overwriting B with X.
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*
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CALL CPPTRS( UPLO, N, NRHS, AP, B, LDB, INFO )
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*
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END IF
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RETURN
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*
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* End of CPPSV
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*
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END
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