Digital

Name

dcreate_ilu_sdia − Generate incomplete Cholesky preconditioner for symmetric diagonal storage

FORMAT

DCREATE_ILU_SDIA (a, ia, ndim, nz, p, ip, n)

Arguments

areal∗8
On entry, a two-dimensional array with dimensions ndim by nz containing the nonzero elements of the matrix A.
On exit, a is unchanged. 

iainteger∗4
On entry, a one-dimensional array of length at least nz,  containing the distances of the diagonals from the main diagonal.
On exit, ia is unchanged. 

ndiminteger∗4
On entry, the leading dimension of array A, as declared in the calling subprogram; ndim >= n.
On exit, ndim is unchanged. 

nzinteger∗4
On entry, the number of diagonals stored in array A.
On exit, nz is unchanged. 

preal∗8
On entry, a two-dimensional array with dimensions ndim by nz.
On exit, array P contains information used by the Incomplete Cholesky preconditioner.

ipinteger∗4
On entry, a one-dimensional array of length at least nz.
On exit, IP contains information for the Incomplete Cholesky preconditioner.

ninteger∗4
On entry, the order of the matrix A.
On exit, n is unchanged. 

Description

DCREATE_ILU_SDIA computes the information required by the Incomplete Cholesky preconditioner for a sparse matrix stored using the symmetric diagonal storage scheme. The arrays P and IP contain the real and integer information, respectively, for use by the preconditioner. 

If the lower triangular part of the matrix A is stored, the decomposition is L ∗ transp(L), where L is a lower triangular matrix. If the upper triangular part is stored, the decomposition is transp(U)∗U, where U is an upper triangular matrix. 

The routine DCREATE_ILU_SDIA is called prior to a call to one of the iterative solver routines with Incomplete Cholesky preconditioning.