appendices:a19
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appendices:a19 [2019/06/27 17:45] helene |
appendices:a19 [2020/08/25 15:46] (current) |
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| ===== Guideline to using GMRES method ===== | ===== Guideline to using GMRES method ===== | ||
| - | KNSYM must be equal to 6 at the 1st line and the 15th column in the loading file. Then the parameters for the iterative method must be entered on the second line with the following format: | + | KNSYM must be equal to 6 at the 1st line and the 15th column in the [[:lagamex|loading file]]. Then the parameters for the iterative method must be entered on the second line (this line is added in the loading file) with the following format: |
| ^Format^Name^Description^Use^Default value^ | ^Format^Name^Description^Use^Default value^ | ||
| | I5 | IM |size of the Krylov subspace (must be inferior to 1000)|GMRES parameter|20| | | I5 | IM |size of the Krylov subspace (must be inferior to 1000)|GMRES parameter|20| | ||
| | I5 | MAXITS |Maximum of iterations allowed |GMRES parameters|5000| | | I5 | MAXITS |Maximum of iterations allowed |GMRES parameters|5000| | ||
| + | | I5 | LFIL | Fill-in tolerance parameter |Preconditioning parameters|50| | ||
| + | | I5 | IOUT | Output unit number for printing intermediate results (=1 printing, =0 no printing)|GMRES parameters| 0| | ||
| + | | G10.0 | EPS | Tolerance for stopping criterion |GMRES parameter|10<sup>-4</sup>| | ||
| + | | G10.0 | DROPTOL |Sets the threshold for dropping small terms in the factorization|Preconditioning parameters| 10<sup>-8</sup>| | ||
| + | | G10.0 | RESTOL |Sets the threshold value of the residual which consider the convergence|GMRES parameters|10<sup>-8</sup>| | ||
| + | ===== Example of parameters as function of number of DOF ===== | ||
| + | === Example 1 === | ||
| + | ^DOF^IM^EPS^LFIL^DROPTOL^ | ||
| + | |26392 |2000 |1.10<sup>-4</sup>| 50| 1.10<sup>-6</sup>| | ||
| + | |14637| 500 |1.10<sup>-4</sup> |100 |5.10<sup>-3</sup>| | ||
| + | |||
| + | === Example 2 === | ||
| + | ^DOF^IM^MAXITS^LFIL^EPS^DROPTOL^ | ||
| + | |42700|20|5000|15|10<sup>-4</sup>|10<sup>-2</sup>| | ||
| + | |58483|175|5000|200|10<sup>-5</sup>|10<sup>-6</sup>| | ||
| + | |||
| + | ===== Effect of the parameters on the convergence ===== | ||
| + | |||
| + | * Higher are IM and LFIL, lower the number of iterations before convergence is. However the memory cost is more important. | ||
| + | * Higher EPS is, lower the number of iterations before convergence for the iterative solver is. However if the residual is not enough low, the out-of-balanced forces diminish slower and the Newton-Raphson can converge slower. | ||
| + | * Higher DROTOL is, lower the memory cost of the preconditioning matrix is. However the number of iterations before convergence for the iterative solver increases. | ||
appendices/a19.1561650356.txt.gz · Last modified: 2020/08/25 15:33 (external edit)
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