dcreate_ilu_sdia 

Generate incomplete Cholesky preconditioner for symmetric diagonal storage

FORMAT

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

Arguments

  a                   real*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.

  ia                  integer*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.

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

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

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

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

  n                   integer*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.