dposv() [1/2]

void linear::lapack::dposv	(	char	UPLO,
		TDmatrix &	A,
		TDmatrix &	B,
		int &	INFO,
		const bool &	debug
	)

Compute the solution to a real system of linear equations A * X = B.

Compute the solution to a real system of linear equations A * X = B.

Parameters

UPLO	(input) CHARACTER*1 = 'U': Upper triangle of A is stored; = 'L': Lower triangle of A is stored.
A	(input/output) DOUBLE PRECISION array, dimension (LDA,N) On entry, the symmetric matrix A. If UPLO = 'U', the leading N-by-N upper triangular part of A con­ tains the upper triangular part of the matrix A, and the strictly lower triangular part of A is not referenced. If UPLO = 'L', the leading N-by-N lower triangular part of A contains the lower tri­ angular part of the matrix A, and the strictly upper triangular part of A is not referenced. On exit, if INFO = 0, the factor U or L from the Cholesky factorization A = U**T*U or A = L*L**T.
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.
INFO	(output) INTEGER = 0: successful exit < 0: if INFO = -i, the i-th argument had an ille­ gal value > 0: if INFO = i, the leading minor of order i of A is not positive definite, so the factorization could not be completed, and the solution has not been computed.
debug	(input) bool switch debug messages on

Definition at line 87 of file dposv_if.cc.

References dposv_(), LINEAR_assert, LINEAR_debug, and LINEAR_LAPACK_failure.

Referenced by dposv(), main(), and test().

  {
    LINEAR_debug(debug, "dposv", "solve system of linear equations");
    // convert to Fortran interfacing array
    typedef aff::FortranArray<TDmatrix> Tfortranarray;
    Tfortranarray FA(A);
    Tfortranarray FB(B);
    LINEAR_assert((FA.last(0)==FA.last(1)),
                  "ERROR (dposv): Matrix A is not a square matrix");
    LINEAR_assert((FB.last(0)==FA.last(0)),
                  "ERROR (dposv): Dimension of right hand side "
                  "does not match");
    f77lapack::integer N=FA.last(0);
    f77lapack::integer NRHS=FB.last(1);
    f77lapack::integer LDA=FA.dimlast(0);
    f77lapack::integer LDB=FB.dimlast(0);
    f77lapack::integer f77INFO;
    f77lapack::doublereal* PA=FA.castedpointer<f77lapack::doublereal>();
    f77lapack::doublereal* PB=FB.castedpointer<f77lapack::doublereal>();
    LINEAR_debug(debug, "dposv", "N: " << N 
               << " NRHS: " << NRHS
               << " LDA: " << LDA
               << " LDB: " << LDB);
    LINEAR_debug(debug, "dposv", "first in A: " << *PA 
               << " first in B: " << *PB);
    f77lapack::dposv_(&UPLO, &N, &NRHS, PA, &LDA, PB, &LDB, &f77INFO);
    LINEAR_debug(debug, "dposv", "INFO: " << f77INFO);
    INFO=f77INFO;
    LINEAR_LAPACK_failure((INFO<0),"dposv",
                          "the -INFO-th argument had an illegal value",
                          INFO);
    LINEAR_LAPACK_failure((INFO>0),"dposv",
                          "the leading INFO-th order is not positive definite",
                          INFO);
  } // dposv

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