SCIP exact mode fails with "SCIP: error in LP solver!" on attached MPS instances

[Ingsoo]

SCIP exact mode fails with SCIP: error in LP solver! on attached exact MIP instances

Summary

MIP instances generated by a PySCIPOpt-based verification tool fail during SCIP
exact solving mode. The failure happens inside model.optimize() with multiple
SCIP internal Error <-6> messages, ending in:

Exception: SCIP: error in LP solver!

Reproduction

The attached no-time-limit configuration is:

bug_reports/scip_lp_error/scip_bug_no_limit.toml

It enables exact SCIP solving and does not set a wall-clock time limit.

To run both case IDs from the attached repository/bundle root:

python scripts/run_obv.py run \
  --config bug_reports/scip_lp_error/scip_bug_no_limit.toml \
  --acceleration-case case_3 \
  --case-list bug_reports/scip_lp_error/scip_lp_error_cases.txt \
  2>&1 | tee bug_reports/scip_lp_error/reproduce_no_limit.log

The two attached case IDs are:

c3_m09_n031_mtf01130400_fs12_x_x_opt540generic
c3_m10_n033_mtf00630001_fs20_x_x_opt730generic

In a captured no-time-limit run on Windows / PySCIPOpt 6.1.0 / SCIP 10.0.2:

• c3_m09_n031_mtf01130400_fs12_x_x_opt540generic failed after about 219
  SCIP log minutes.
• c3_m10_n033_mtf00630001_fs20_x_x_opt730generic failed after about 22
  SCIP log seconds.

The captured run directory is:

bug_reports/scip_lp_error/results_no_limit/scip_lp_error_repro_no_limit/case_3/20260601_092757

The second case can be reproduced quickly on its own:

python scripts/run_obv.py run \
  --config bug_reports/scip_lp_error/scip_bug_no_limit.toml \
  --acceleration-case case_3 \
  --case-list bug_reports/scip_lp_error/scip_lp_error_case2_only.txt \
  2>&1 | tee bug_reports/scip_lp_error/reproduce_no_limit_case2.log

The second case also reproduces quickly in the captured no-time-limit
single-case run reproduce_no_limit_case2.log.

The exported MPS files can also be replayed directly:

python bug_reports/scip_lp_error/reproduce_mps.py \
  bug_reports/scip_lp_error/results_no_limit/scip_lp_error_repro_no_limit/case_3/*/cases/*/model.mps \
  2>&1 | tee bug_reports/scip_lp_error/reproduce_mps.log

Expected Behavior

SCIP should either solve the instances, prove infeasibility, hit the configured
time limit, or return a regular solver status without an internal LP solver
exception.

Actual Behavior

SCIP emits internal Error <-6> messages and PySCIPOpt raises:

Exception: SCIP: error in LP solver!

Attachments

• reproduce_no_limit.log
• reproduce_no_limit_case2.log
• results_no_limit/scip_lp_error_repro_no_limit/case_3/20260601_092757/summary.jsonl
• results_no_limit/scip_lp_error_repro_no_limit/case_3/20260601_092757/error_case_ids.txt
• environment.txt
• generated model.mps files
• reproduce_mps.py
• scip_bug_no_limit.toml
• scip_lp_error_cases.txt
• scip_lp_error_case2_only.txt

scip_lp_error_repro.zip