[Users] bug in Dissipation thorn?

[Bruno Giacomazzo]

On Feb 22, 2013, at 10:38 AM, Kentaro Takami wrote:

> Further strange behavior:
> When I insert non-essential line such as "WRITE(*,*)" statement
> in "apply_dissipation.F77", sometimes the difference is disappeared.
> So, I doubted incorrect pointer position.


	could it be related to compiler optimization?

	I remember seeing things similar to this in the past, when adding a line like that was changing the behavior of the code. In my case, it was having or not a segfault, which at the end depended on how the compiler was actually compiling the code and that seemed to be somehow dependent on the length of the routine. This is a problem I had few years ago so I don't remember exactly all the details, but we fixed it by changing the code in order to be sure that certain operations were always executed in the same order (I think it had to do with an if condition being located inside or outside a do loop).

Cheers,
Bruno

Dr. Bruno Giacomazzo
JILA - University of Colorado
440 UCB
Boulder, CO 80309
USA

Tel.  : +1 303-492-5170
Fax  : +1 303-492-5235
email : bruno.giacomazzo at jila.colorado.edu
web: http://www.brunogiacomazzo.org

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