Posted Mon, 02 Jun 2008 07:03:45 GMT by Samir Ennour
Hello,

When i run my model i see this message

PCG results in 1000 steps only a relative accuracy with an error 5e-8
value of beta:1.133e2 indicates an instable preconditioning


but in the iteration the model converge.

What means this error and the final result is true or no
Posted Tue, 10 Jun 2008 08:37:02 GMT by Boris Lyssenko
You are using a preconditioned conjugant gradient (PCG) solver for solving the equation system. The message indicates that the preconditioning part did not succeed. In general this points out that there is a stability problem in the model. So even if the model converges after that, I would try to identify the reason for the instable preconditioning. If the message is shown in only one time step of a transient solution, however, you might also just accept that. It is hard to say in a general case what the effects on the results are as the message only indicates the instability of a mathematical operation.

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