[SCIP] SCIProwGetObjParallelism assert query

[Marc Pfetsch]

Hi James,

in exact arithmetic parallelism should be at most 1. If this is not the 
case, this might signify an error. This is why there is an assert. Or 
the problem might occur because of numerical problems (you numbers look 
quite big). In any case, the issue will be ignored in optimized mode.

If you want to enable some additional checks, you can add "#define 
SCIP_MORE_DEBUG" at the top of lp.c, recompile and run. SCIP will then 
check whether the values use in the function below are reasonably close 
to the ones that it would get by recomputing the values. Note that this 
will slow down execution.

Best

Marc



On 23/06/2023 16:55, James Cussens wrote:
> Hi all,
> 
> I'm getting the following assert error when running in OPT=dbg mode 
> (everything else default compilation options):
> 
> gobnilp: src/scip/lp.c:7820: SCIProwGetObjParallelism: Assertion 
> `SCIPsetIsSumLE(set, parallelism, 1.0)' failed.
> 
> The relevant code from lp.c is:
> 
>     parallelism = SCIPsetIsPositive(set, prod) ? REALABS(row->objprod) / 
> SQRT(prod) : 0.0;
>     assert(SCIPsetIsSumGE(set, parallelism, 0.0));
>     assert(SCIPsetIsSumLE(set, parallelism, 1.0));
>     parallelism = MIN(parallelism, 1.0);
>     parallelism = MAX(parallelism, 0.0);
> 
> If it is reasonable to assert that parallelism is <= 1.0, then why do we 
> need the "parallelism = MIN(parallelism, 1.0);" line?
> 
> Here are the values that are causing the assert error:
> [lp.c:7819] debug: 
> |row->objprod|=5.66927e+07,prod=7.62443e+14,parallelism=2.05316
>  
> James
> 
> James Cussens
> Room MVB 3.26
> Dept of Computer Science, University of Bristol
> Phone: +44 (0)117 455 8723
> https://jcussens.github.io/ <https://jcussens.github.io/>
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