# JoSIM®-Pro reports that the matrix has no solution

Reduce the circuit and check its reference, topology, model values and initial conditions before treating the error as a numerical tuning problem.

## Compatibility

2.9.0 release target; review-build/source evidence

Published guidance with release-applicability limits. Confirm package applicability before following this guide.

## Isolate the cause

1. Read the first diagnostic and reduce the netlist to the smallest circuit that reproduces it.
2. Check the intended reference node and floating subcircuits or inconsistent ideal-source constraints.
3. Verify units, model parameters, coupled-inductor validity, bias and initial conditions.
4. Restore parts of the circuit in small steps and compare against a supplied working example.

## Preserve the physical circuit

Do not add an arbitrary resistor solely to suppress the message. A corrected circuit resolved a historical zero-resistance-loop report without the proposed artificial resistance.

A weak reference or finite impedance may be physically appropriate for some models, but it changes the circuit. Document and validate that choice rather than treating it as a universal solver repair.

## Sources and verification details

Recorded inputs/builds only. Complete walkthrough and final-package acceptance remain separate.



- support:SUP-013: Generalised editorial finding; outcome qualification retained
- josim-pro:docs/manual_source/sections/troubleshooting.tex: The simulation starts but fails, diverges, or produces no useful result
- josim-pro:docs/manual_source/sections/syntax.tex: Node and component syntax; mutual coupling
- owner:technical-review-20261102: JoSIM-Pro 2.9 chosen as the public starting path; release availability must be checked before publication

- Support history informed this draft. Current-source guidance has been checked; a fresh walkthrough on the intended distributed release and product-owner review remain pending.

## Related guides

- [Coupled inductors cause divergence or invalid-matrix errors](/knowledge-base/josim-coupling-validity)
- [A junction model is missing or behaves like the wrong model](/knowledge-base/josim-model-syntax)
- [Prepare a useful support report without exposing a licence or private design](/knowledge-base/support-effective-report)