[Carpet] Bugzilla Bug 118

[Ian Hinder]

Erik Schnetter wrote:
> On May 2, 2008, at 17:50:53, Ian Hinder wrote:
> 
>> Ian Hinder wrote:
>>
>>> The eps with which the times are being compared in CarpetLib is 1e-12,
>>> but the two times here are different by 1.36e-12, so the error is
>>> triggered.  I am rerunning with a larger eps value to make sure nothing
>>> else is wrong.  This happens at t = 586.500 - I don't know why Carpet is
>>> saying 2736.
>>
>> The run with the larger eps value passed the point at which the old run
>> crashed.
> 
> 
> Ian,
> 
> I found the source of the problem.  This comparison expects an absolute
> accuracy of 1e-12, which is obviously wrong, it should requite 1e-12 as
> relative accuracy.  Burkhard Zink just came across a similar error in
> Carpet.  I expect to push corrections soon.

I just had a similar problem with the following code.  Is it the same
problem?  This is in Evolve.cc, line 374. It asserts on the comparison
with eps.


              // Advance times

              cctkGH->cctk_time
                = (global_time
                   - delta_time / maxtimereflevelfact
                   + delta_time * mglevelfact / timereflevelfact);
              CCTK_REAL const carpet_time = cctkGH->cctk_time / delta_time;
              for (int m=0; m<maps; ++m) {
                vtt.at(m)->advance_time (reflevel, mglevel);
                CCTK_REAL const eps = 1.0e-12;
                static_assert (abs(0.1) > 0,
                               "Function CarpetLib::abs has wrong
signature");
                CCTK_REAL const level_time =
                  vtt.at(m)->get_time (reflevel, mglevel);
                assert (abs (level_time - carpet_time) < eps);
                vtt.at(m)->set_time (reflevel, mglevel, carpet_time);
              }




> 
> -erik
> 
> 
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-- 
Ian Hinder
hinder at gravity.psu.edu
http://www.gravity.psu.edu/~hinder