[SCIP] LP numerical troubles.

[Marc Pfetsch]

Hi James,

you could add

SCIP_CALL( SCIPwriteLP(set->scip, "debug.lp") );

at solve.c:4624. This will write out the current LP.

Also a good idea is to turn on the parameter "display/lpinfo". This will 
show the output of the LP-solver.

Best

Marc




On 28/10/2022 13:55, James Cussens wrote:
> ​Hi all,
> 
> In a SCIP project I am working on I am continually running into 
> "unresolved numerical troubles in LP". Some example output given below. 
> I get this whether using SOPLEX or CPLEX and whether or not I link with 
> IPOT. I suspect that I am somehow generating "weird" LPs so I would like 
> to inspect the LPs that are causing these problems. What's the best way 
> to do this? (Btw, I am using both pricing and cutting in the 
> price-and-cut loop.)
> 
> I'm using SCIP 8.0.2
> 
> James
> 
> 
> time | node  | left  |LP iter|LP it/n|mem/heur|mdpt |frac |vars |cons 
> |cuts |sepa|confs|strbr|  dualbound   | primalbound  |  gap   | compl.
> p 3.7s|     1 |     0 |    14 |     - |shiftand|   0 |   - |9815 | 853 | 
>    0 |  0 |   6 |   0 |      --      |-5.916805e+03 |    Inf | unknown
> (node 1) unresolved numerical troubles in LP 5 -- using pseudo solution 
> instead (loop 1)
> k 3.8s|     1 |     0 |    16 |     - |roundand|   0 |   - |9815 | 853 | 
>    0 |  0 |   6 |   0 |      --      |-2.814319e+03 |    Inf | unknown
>    3.9s|     1 |     2 |    16 |     - |    91M |   0 |   - |9815 | 853 
> |   0 |  0 |   6 |   0 |      --      |-2.814319e+03 |    Inf | unknown
>    3.9s|     2 |     3 |    18 |  16.0 |    91M |   1 |   - |9815 | 853 
> |   0 |  0 |   6 |   0 |      --      |-2.814319e+03 |    Inf | unknown
>    4.0s|     3 |     4 |    22 |  10.0 |    91M |   2 |   - |9815 | 853 
> |   0 |  0 |   6 |   0 |      --      |-2.814319e+03 |    Inf | unknown
>    4.0s|     4 |     5 |    24 |   7.3 |    91M |   3 |   - |9815 | 853 
> |   0 |  0 |   6 |   0 |      --      |-2.814319e+03 |    Inf | unknown
>    4.0s|     5 |     6 |    26 |   6.0 |    91M |   4 |   - |9815 | 853 
> |   0 |  0 |   6 |   0 |      --      |-2.814319e+03 |    Inf | unknown
>    4.0s|     6 |     7 |    28 |   5.2 |    91M |   5 |   - |9815 | 853 
> |   0 |  0 |   6 |   0 |      --      |-2.814319e+03 |    Inf | unknown
> [solve.c:4624] ERROR: (node 7) unresolved numerical troubles in LP 10 -- 
> aborting
> [solve.c:4984] ERROR: Error <-6> in function call
> [scip_solve.c:2771] ERROR: Error <-6> in function call
> [scipshell.c:101] ERROR: Error <-6> in function call
> [scipshell.c:468] ERROR: Error <-6> in function call
> [cmain.c:104] ERROR: Error <-6> in function call
> SCIP Error (-6): error in LP solver
> 
> 
> 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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