Page 624 - ExtendSim User Guide
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Model Execution
Simulation setup
Choice
Use database table__Seed for values
Check blocks for duplicate random number seeds
Use recommended random number gen- erator (default)
Antithetic random variates (off by default)
Description
When this option is selected from the popup menu, the starting seed for each consecutive run is read from the __Seed table in the selected Extend- Sim database. This option allows you to specify exactly which seeds will be used for each simulation run. It also is a convenient method for record- ing a set of seed values. To specify a set of random seeds, create a table in a database with one field and a number of records equal to the number of simulation runs. The model will access sequential records for each consec- utive simulation run, and that record’s value will be the seed value for the run. If you leave the records blank or enter zeros, ExtendSim will fill the table with seed values on the first run. It will then use those seed values for each subsequent set of runs.
At the start of the simulation, all blocks that use random numbers are checked to make sure that no two blocks are using the same seed values. This option is not necessary unless the use block seed option is selected in the individual blocks.
When checked, ExtendSim will use the recommended Minimum Stan- dard random number generator. When unchecked, ExtendSim will use the optional Schrage random number generator used in previous versions (backwards compatibility). For details about the ExtendSim random num- ber generator see “Random number generators” on page 703.
Generates antithetic variates for possible variance reduction using multiple runs. It can be controlled by the Optimizer block (Value library), or by cus- tom blocks, to alternate on and off in alternate runs using the Antitheti- cRandomVariates global variable. See the ExtendSim Developer Reference for more information. This setting should be off under normal use.
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