@RISK: Simulation Crashes with Increased Number of Iterations

Crashes at high iterations are usually caused by Multiple CPU mode. Disable Multiple CPU to confirm and avoid worker Excel failures.

Jan 20, 2026
Knowledge

Title

Answer

Applies to:
@RISK 6.x and Up

My simulation crashes when I increase iterations. Why?

This is usually caused by Multiple CPU mode. When iterations increase, @RISK may switch from single-CPU to multiple-CPU execution. In multiple-CPU mode, @RISK launches invisible “worker” copies of Excel and coordinates them from the main (master) Excel. On some systems, starting or shutting down these worker Excels fails, causing Excel to appear frozen or to crash.

If the crash happens at 100% complete, you can often recover results by opening Task Manager, finding the extra Excel.exe processes (the ones using less memory), and ending those tasks. Once the workers close, the master Excel will finish cleanup and results will be available.

To confirm the cause, rerun the simulation with Simulation Settings » General » Multiple CPU set to Disabled. If it completes successfully, the issue is with multi-CPU startup or shutdown on your system.

Progress Window Freezes at "Initializing ... 100%".

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