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<div class="">Hi Sajid,</div>
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Can you please try this branch hongzh/fix-computejacobian quickly and see if it makes a difference?
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<div class="">Thanks,</div>
<div class="">Hong (Mr.)<br class="">
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<div class="">On May 16, 2019, at 8:04 PM, Sajid Ali via petsc-users <<a href="mailto:petsc-users@mcs.anl.gov" class="">petsc-users@mcs.anl.gov</a>> wrote:</div>
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<div dir="ltr" class="">While there is a ~3.5X speedup, deleting the aforementioned 20 lines also leads the new version of petsc to give the wrong solution (off by orders of magnitude for the same program).
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<div class="">I tried switching over the the IFunction/IJacobian interface as per the manual (page 146) which the following lines :<br class="">
```<br class="">
TSSetProblemType(ts,TSLINEAR);<br class="">
TSSetRHSFunction(ts,NULL,TSComputeRHSFunctionLinear,NULL);<br class="">
TSSetRHSJacobian(ts,A,A,TSComputeRHSJacobianConstant,NULL);<br class="">
```<br class="">
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<div class="">are equivalent to :<br class="">
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<div class="">```<br class="">
TSSetProblemType(ts,TSLINEAR);<br class="">
TSSetIFunction(ts,NULL,TSComputeIFunctionLinear,NULL);<br class="">
TSSetIJacobian(ts,A,A,TSComputeIJacobianConstant,NULL);<br class="">
```<br class="">
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But the example at src/ts/examples/tutorials/ex3.c employs a strategy of setting a shift flag to prevent re-computation for time-independent problems. Moreover, the docs say "using this function (TSComputeIFunctionLinear) is NOT equivalent to using TSComputeRHSFunctionLinear()"
and now I'm even more confused.<br clear="all" class="">
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<div class="">PS : Doing the simple switch is as slow as the original code and the answer is wrong as well.
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<div class="">Thank You,<br class="">
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<div style="font-size:12.8px" class="">Sajid Ali<br class="">
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<div style="font-size:12.8px" class="">Applied Physics<br class="">
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<div style="font-size:12.8px" class="">Northwestern University</div>
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