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Merge pull request #26469 from ke7kto/parallelsubsetdocs
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Update ParallelSubsetSimulation docs closes #26468
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grmnptr authored Jan 9, 2024
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Expand Up @@ -105,21 +105,31 @@ chains, the `AdaptiveMonteCarloDecision` class
is used for decision-making. Please refer to [AdaptiveMonteCarloDecision](AdaptiveMonteCarloDecision.md)
for more details.

If the parameter [!param](/Samplers/ParallelSubsetSimulation/use_absolute_value) is `True`, the absolute
value of [!param](/Samplers/ParallelSubsetSimulation/output_reporter) will be maximized.
As such, a least-squares fit optimization can be achieved by passing the negative of the sum-squared error
into the value of [!param](/Samplers/ParallelSubsetSimulation/output_reporter) with
[!param](/Samplers/ParallelSubsetSimulation/use_absolute_value) set to `True`. Otherwise
the value of [!param](/Samplers/ParallelSubsetSimulation/output_reporter) will be maximized after its absolute value is taken.

## Example Input Syntax

The input file for using the PSS algorithm is somewhat similar to the other sampler
classes except for three differences. First, the `Samplers` block is presented below:

!listing modules/stochastic_tools/test/tests/samplers/ParallelSubsetSimulation/pss.i block=Samplers

where, `num_samplessub` is the number of samples per subset and `num_subsets` is the number of subsets.
`inputs_reporter` and `output_reporter` are the reporter values which transfer
information between the `ParallelSubsetSimulation` sampler and the `AdaptiveMonteCarloDecision` reporter. There is an optional input parameter `subset_probability` which has been defaulted to
where, [!param](/Samplers/ParallelSubsetSimulation/num_samplessub) is the number of samples per subset and
[!param](/Samplers/ParallelSubsetSimulation/num_subsets) is the number of subsets.
[!param](/Samplers/ParallelSubsetSimulation/inputs_reporter) and [!param](/Samplers/ParallelSubsetSimulation/output_reporter)
are the reporter values which transfer
information between the `ParallelSubsetSimulation` sampler and the `AdaptiveMonteCarloDecision` reporter. There is an optional
input parameter [!param](/Samplers/ParallelSubsetSimulation/subset_probability) which has been defaulted to
`0.1`, meaning that there are $1/0.1$ samples per Markov chain. This can, however, be
changed as per the user preference. `num_parallel_chains` is also an optional parameter
changed as per the user preference. [!param](/Samplers/ParallelSubsetSimulation/num_parallel_chains) is also an optional parameter
that explicitly specifies the number of Markov chains to be run in parallel per subset.
If `num_parallel_chains` is not specified, the number of parallel Markov chains per subset
will be equal to the number of processors. Besides, `use_absolute_value` can be set to true
If [!param](/Samplers/ParallelSubsetSimulation/num_parallel_chains) is not specified, the number of parallel Markov chains per subset
will be equal to the number of processors. Besides, [!param](/Samplers/ParallelSubsetSimulation/use_absolute_value) can be set to true
when failure is defined as a non-exceedance rather than an exceedance.

Second, the `Reporters` block is presented below with the `AdaptiveMonteCarloDecision` reporter:
Expand All @@ -133,7 +143,7 @@ Third, the `Executioner` block is presented below:
!listing modules/stochastic_tools/test/tests/samplers/ParallelSubsetSimulation/pss.i block=Executioner

where it is noticed that unlike some other sampler classes, the `type` is transient.
The number of time steps is automatically determined based on `num_samplessub`, `num_subsets` and the number of processors used.
The number of time steps is automatically determined based on [!param](/Samplers/ParallelSubsetSimulation/num_samplessub), [!param](/Samplers/ParallelSubsetSimulation/num_subsets) and the number of processors used.


## Output format
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