Hi,

I get relatively comparable results for both versions:

dev: ./step-23  55.55s user 1.64s system 131% cpu 43.637 total
8.0: ./step-23  55.85s user 1.48s system 129% cpu 44.130 total

Is this the unmodified step-23 tutorial program?

For measuring performance regressions a total runtime of less than 5
seconds doesn't say that much. Never versions allocate and precompute
quite a bunch of stuff upfront which might result in a small (problem
independent) fixed runtime overhead (of a second or less).

Best,
Matthias



On Tue, Dec 26, 2017, at 05:52 CST, [email protected] wrote:

> Deal.II 8.5.1 seems to be 20% slower than 8.0.0. This is the timing I get 
> when running the Step-23 tutorial (output to screen and vtk is suppressed):
>
> deal.II version 8.0.0:
>
> $ time ./step-23 
> Number of active cells: 16384
> Number of degrees of freedom: 16641
>
> real    0m3.432s
> user    0m6.320s
> sys    0m0.612s
>
> deal.II version 8.5.1:
>
> $ time ./step-23 
> Number of active cells: 16384
> Number of degrees of freedom: 16641
>
> real    0m4.430s
> user    0m7.080s
> sys    0m0.492s
>
> In general, I get about 20% slow down for my own code when upgrading from 
> 8.0.0 to 8.5.1. What is the reason of such a slow down? Does the deal.II 
> follow the right direction given new versions become gradually slower?!

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