ESTS0167 ICCG2.

1. NAME OR DESIGNATION OF PROGRAM:  ICCG2.

3. DESCRIPTION OF PROGRAM OR FUNCTION

ICCG2 (Incomplete Cholesky factorized Conjugate Gradient algorithm for 2-D symmetric problems)  was developed to solve a linear symmetric matrix system arising from a 9-point discretization of two-dimensional elliptic and parabolic partial differential equations found in plasma physics applications, such as resistive MHD, spatial diffusive transport, and phase space  transport (Fokker-Planck equation) problems. These problems share the common feature of being stiff and requiring implicit solution techniques. When these parabolic or elliptic PDE's are discretized with finite-difference or finite-element methods, the resulting matrix system is frequently of block-tridiagonal form. To use ICCG2, the discretization of the two-dimensional partial differential equation and its boundary conditions must result in a block- tridiagional supermatrix composed of elementary tridiagonal matrices. The incomplete Cholesky conjugate gradient algorithm is used to solve the linear symmetric matrix equation. Loops are arranged to vectorize on the Cray1 with the CFT compiler, wherever possible. Recursive loops, which cannot be vectorized, are written for optimum scalar speed. For matrices lacking symmetry, ILUCG2 should be used. Similar methods in three dimensions are available in ICCG3 and ILUCG3. A general source containing extensions and macros, which must be processed by a precompiler to obtain the standard FORTRAN source, is provided along with the standard FORTRAN source because it is believed to be more readable. The precompiler is not included, but precompilation may be performed by a text editor as described in the UCRL-88746 Preprint.

4. METHOD OF SOLUTION:

5. RESTRICTIONS ON THE COMPLEXITY OF THE PROBLEM:

6. TYPICAL RUNNING TIME:

7. UNUSUAL FEATURES OF THE PROGRAM:

8. RELATED AND AUXILIARY PROGRAMS:

10. REFERENCES

- D.V. Anderson,
  ICCG3: Subprograms for the Solution of a Linear Symmetric Matrix
  Equation Arising from a 7, 15, 19 or 27 Point 3D Discretization,
  Computer Physics Communications, Vol. 30, No.1, pp. 51-57, 1983,
  also available as UCRL-88746 Preprint (February 1983).

- D.V. Anderson and A.I. Shestakov:
  ICCG2 - Subprograms for the Solution of a Linear Symmetric Matrix
  Equation Arising from a 9-Point Discretization
  UCRL-88744 Preprint (February 1983).

11. MACHINE REQUIREMENTS

At least 14*mn, where mn is the number of linear equations.

13. OPERATING SYSTEM UNDER WHICH PROGRAM IS EXECUTED:  CTSS.

14. OTHER PROGRAMMING OR OPERATING INFORMATION OR RESTRICTIONS:

15. NAME AND ESTABLISHMENT OF AUTHORS

- Anderson, D.V.
  Lawrence Livermore National Lab., CA (United States).

source program   mag tapeICCG2 General Source                       SRCTP
source program   mag tapeICCG2 FORTRAN Source                       SRCTP
report                   UCRL-88744 Preprint (February 1983)        REPPT