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Run Model Options

Run Model has no dialog. Its two settings are the lists beside it on the ribbon, and the Custom Run menu holds two dialogs of its own.

The Sampling list

How the input values are drawn: Monte Carlo or Sobol (Quasi-Random). Monte Carlo draws pseudo-random values; Sobol draws a quasi-random sequence that covers the input space more evenly.

Choosing Sobol changes the counts the Simulations list offers, because a Sobol sequence covers the input space evenly only at a power of two.

Above 1,000 random inputs the engine falls back to Monte Carlo sampling by itself, even when Sobol was asked for. The report says which sampler actually ran.

The Simulations list

How many trials. The counts offered depend on the sampler:

Sampling	Counts offered
Monte Carlo	1,000 / 10,000 / 100,000 / 1,000,000 / 10,000,000 / 100,000,000
Sobol (Quasi-Random)	1,024 / 16,384 / 131,072 / 1,048,576 / 16,777,216 / 134,217,728

Neither list is stored in the workbook. Both reset to their defaults each time Excel loads the add-in.

Custom Run > Run Fast Mode

Twelve buttons in two headed groups, Monte Carlo and Sobol (Quasi-Random), carrying the same counts the Simulations list offers for each sampler. Each button names its own sampler, so it does not read the ribbon's Sampling list.

Custom Run > Run Native Mode

Three buttons under a Monte Carlo heading: 1,000, 10,000 and 100,000 Simulations. Each runs in Native Mode, skipping the parser engine, and each says so:

Run in Native Mode (Excel recalculation), skipping the parser engine, for the chosen number of simulations.

The list stops at 100,000 because Native Mode is capped at 100,000 simulations, which the largest button states on itself. The cap exists because a Native Mode trial is a full Excel recalculation of the workbook, so the cost per trial is far higher than in Fast Mode.

A second heading below them, Sobol (Quasi-Random) (Pending), carries three more counts that are not built:

Not implemented yet. Native Mode always draws Monte Carlo values.

Those three are 1,024, 16,384 and 65,536, and that last one is 65,536 rather than 131,072 for the same reason: 131,072 is over the 100,000 cap. They belong to the pending Sobol group, not to the three working Native Mode counts above.

Custom Run > Custom...

Asks for any count you like, in a dialog titled N Simulations with one box:

Number of simulations (10 to 100,000,000)

An entry outside that range is refused:

Enter a whole number of simulations between 10 and 100,000,000.

Custom Run > Set up Histogram Groups...

One row per output, each with a group. The dialog says what a group does:

Outputs sharing a group are drawn together on one overlaid histogram.

Outputs left in different groups get a histogram each. Nothing here is saved to the workbook.

What is not on this ribbon

Run Native Mode with Sobol sampling is on the menu but is not built, and its label carries (Pending) so you can see that without clicking. The same is true of Sensitivity Analysis and the Options button.