[Users] bug in Dissipation thorn?

Kentaro Takami kentaro.takami at aei.mpg.de
Fri Feb 22 13:23:56 CST 2013

Hi, Ian,

> What quantity is different, and by how much?  What happens if you compile without optimisation?  Are the differences present in the initial data, or just after some evolution steps?  How many steps?  Where in the grid do the differences appear?

I compared HDF5 checkpoint files.
The difference is only last a few digit, but it is grow up after
several iterations.

The checkpoint files in iteration "0" are exactly same and
evolution step create such a difference.
For my test case,
it=1, 2nd step in RK : kxx and so on become random.
it=1, 3rd step in RK: hydro variable also become random.

Furthermore ,
if I use O1 in optimization flag, I don't see difference.
On the other hand, if I use O2, random difference is appeared.


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