cuOptCreateProblem fails on num_constraints=0 (zero-row problems)

Aperta
  • Qualcosa non va?
#2,006 1 commento 0 reazioni 1 assegnatario Vedi su GitHub

I maintainer di solito rispondono entro 1 giorno

@aliceb-nv ci sta già lavorando.

Dal 29/9/2026.

Valutazione

Questa issue non è ancora stata valutata.

Descrizione

Summary

cuOptCreateProblem fails with CUOPT_INVALID_ARGUMENT for any problem with zero linear constraints — including pure bound-constrained LPs and QCQP-style problems (quadratic constraints only, no linear rows).

Repro (Java, but this is a C API issue)

try (Problem problem = new Problem("no-constraint")) {
  Variable x = problem.addVariable(0.0, 10.0, 1.0, VariableType.CONTINUOUS, "x");
  problem.setObjective(x, ObjectiveSense.MINIMIZE);
  try (Solution solution = problem.solve()) {  // throws here
    System.out.println(solution.getTerminationStatus());
  }
}

Exception in thread "main" com.nvidia.cuopt.mathematicaloptimization.CuOptException: cuOptCreateProblem failed with status 1
	at com.nvidia.cuopt.mathematicaloptimization.NativeCuOpt.createProblem(Native Method)
	...

Same failure with any zero-linear-constraint problem, e.g. a QuadraticExpression constraint with no linear rows, or a single SEMI_CONTINUOUS variable with no addConstraint calls at all.

Root cause (traced, not fixed)

cuOptCreateProblem (cpp/src/pdlp/cuopt_c.cpp:338) has no explicit num_constraints <= 0 check itself — unlike sibling functions such as cuOptSetInitialDualSolution, which does. The failure comes from a raft::exception thrown somewhere inside problem->set_csr_constraint_matrix(...) (or a related setter) on a zero-row CSR matrix, caught and converted to CUOPT_INVALID_ARGUMENT. Not traced further than that.

Why this looks unintentional

  • No explicit validation rejects it at the API boundary (contrast with the num_constraints <= 0 check present elsewhere in the same file).
  • Pure bound-constrained LPs and quadratic-only-constrained problems are mathematically valid; other solvers support them.

Impact

Found while writing/testing Java doc examples for #1999 — had to add an artificial non-binding linear constraint to two examples (quadratic-constraint-only, and a semi-continuous variable with no other constraints) purely to work around this.

Ask

Could someone with more context on the CSR/problem construction path confirm whether zero-row problems are meant to be supported, and if so where the fix belongs?

Lingua principale
Cuda
Stelle
1.1k
Fork
249
Merge medio
1g 15h
PR unite (30g)
126

Preparare l'ambiente

Come iniziare

  1. Leggi tutta la issue e poi la guida ai contributi del progetto.
  2. Commenta sulla issue per dire che te ne occupi tu — evita che due persone facciano lo stesso lavoro.
  3. Fai un fork del repository e lavora su un branch.
  4. Apri una pull request che faccia riferimento al numero della issue.

Altre issue di NVIDIA/cuopt

Tutte le issue di NVIDIA/cuopt

Ricevi le nuove issue nella tua casella

Un breve riepilogo di issue GitHub adatte ai principianti.