Thread View: sci.math.num-analysis
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Started by Dennis Moon
Tue, 27 Oct 1992 14:03
Pre-Conditioned CG NOT CONVERGING
Author: Dennis Moon
Date: Tue, 27 Oct 1992 14:03
Date: Tue, 27 Oct 1992 14:03
21 lines
1224 bytes
1224 bytes
A friend without news access is having trouble with solving the matrices in his magneto-hydrodynamic code. The equation is the standard Ax=b, where the solution vector x is 4096 elements. The matrix is sparse, with 5 non-zero elements per row. He is using a CG solver with LU factorization. For most time steps it converges in about 10 iterations, but on some timesteps it will not converge no matter how many iterations. He has tried both a hand coded solver and routines from the IBM Risc6000 ESSL library with the same result. What other solution techniques should he be looking at? Is this an indication that in some sense the problem is not well posed? What matrix characteristics can be used to pre-diagnose this problem? Any comments would be welcome, his thesis depends on this Thanks Dennis Moon dam@ssesco.com
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