uk.ac.soton.simulation.jsit.anylogic

Class RandomWithSeedAccess

java.lang.Object

java.util.Random

uk.ac.soton.simulation.jsit.anylogic.RandomWithSeedAccess

All Implemented Interfaces:

java.io.Serializable, SeedAccessibleRNG

public class RandomWithSeedAccess
extends java.util.Random
implements SeedAccessibleRNG, java.io.Serializable

Random subclass that keeps a copy of the seed so that it is accessible (and so can be written out to promote experiment reproducibility). It also has the option to allocate sequential seeds (from a fixed base) for each instantiation, so that you can have AnyLogic multi-run experiments with stochastic variation that are still all reproducible. (This is not possible using the AnyLogic default, since setting a fixed seed applies that to all runs, and thus there is no stochastic variation per run).

To use it, this class has to be instantiated as a custom generator in the experiment's Randomness section.

If you use incremented seeds from a fixed base, AnyLogic's threading strategies mean that the actual seed per run may not be what you expect. When giving a base seed S in the experiment, then for

• single run experiments: creates one Engine instance but with 2 RNGs (because one is created per thread and the model is initialised in one thread but runs in another). Run gets seed S+1
• N-run multi-run non-parallel experiments: creates one Engine instance but with N+1 RNGs. (I think this is one model initialisation thread, and then N model-run threads). Runs get seeds S+1, S+2, ...
• N-run multi-run parallel experiments: creates one Engine instance with C (num cores) RNGs, and one separate Engine instance (even if there are <C runs). Runs get seeds S+C+1, S+C+2, ...

This also means that random samples during model initialisation may be using a different RNG to those during model execution!

(Use the three-parameter constructor in your experiments to see this.)

Since:

0.1

Author:

Stuart Rossiter

See Also:

Serialized Form

Constructor Summary

Constructors

Constructor and Description
RandomWithSeedAccess() Create an instance with a 'random' seed; we actually use the current system time in milliseconds, which will always vary between instantiations.
RandomWithSeedAccess(long seed) Convenience constructor to create an instance with the specified seed.
RandomWithSeedAccess(long seed, boolean incrementFromFixedBase) Create an instance with the given seed, specifying whether you want future invocations to increment the actual seed from the one given here.
RandomWithSeedAccess(long seed, boolean incrementFromFixedBase, com.anylogic.engine.Engine _e) Test-only version of the constructor where the relevant AnyLogic Engine instance is passed in, and AnyLogic traceln calls are made to show you information about the instantiation calls.

Method Summary

Modifier and Type	Method and Description
static java.lang.Long	getBaseSeed() Get the base seed used where you have created instances with incrementFromFixedBase set to true (otherwise returns null).
long	getSeed() Get the seed value used for this instance (as per SeedAccessibleRNG interface).

Methods inherited from class java.util.Random

doubles, doubles, doubles, doubles, ints, ints, ints, ints, longs, longs, longs, longs, nextBoolean, nextBytes, nextDouble, nextFloat, nextGaussian, nextInt, nextInt, nextLong, setSeed

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

RandomWithSeedAccess

public RandomWithSeedAccess()

Create an instance with a 'random' seed; we actually use the current system time in milliseconds, which will always vary between instantiations.

Since:

0.1

RandomWithSeedAccess

public RandomWithSeedAccess(long seed)

Convenience constructor to create an instance with the specified seed. This is the same as calling RandomWithSeedAccess(seed, false).

Parameters:

seed - The seed value.

Since:

0.1

RandomWithSeedAccess

public RandomWithSeedAccess(long seed,
                            boolean incrementFromFixedBase)

Create an instance with the given seed, specifying whether you want future invocations to increment the actual seed from the one given here. The latter allows you to have reproducible runs from an AnyLogic multi-run experiment (e.g., Monte Carlo) whilst maintaining stochastic variation per run, since the invocation code in the 'custom generator' dialog will be re-called for each run.

See the notes at the top of this class for important information about what incremented seeds will actually get applied for each run.

Parameters:

seed - The seed value.

incrementFromFixedBase - Whether to use the seed value as a base for future invocations (where the seed value specified will be ignored).

Since:

0.2

RandomWithSeedAccess

public RandomWithSeedAccess(long seed,
                            boolean incrementFromFixedBase,
                            com.anylogic.engine.Engine _e)

Test-only version of the constructor where the relevant AnyLogic Engine instance is passed in, and AnyLogic traceln calls are made to show you information about the instantiation calls.

Parameters:

seed - The seed value. (Will be ignored if incrementFromFixedBase is true and this is not the first instantiation.)

incrementFromFixedBase - Whether to increment the seeds used in each future instantiation from the seed value (as a fixed base).

_e - A reference to the AnyLogic Engine. In an Experiment's randomness settings, this is available as _e or via the getEngine() call.

Since:

0.2

Method Detail

getBaseSeed

public static java.lang.Long getBaseSeed()

Get the base seed used where you have created instances with incrementFromFixedBase set to true (otherwise returns null).

Returns:

The base seed used.

Since:

0.1

getSeed

public long getSeed()

Get the seed value used for this instance (as per SeedAccessibleRNG interface).

Specified by:

getSeed in interface SeedAccessibleRNG

Returns:

The seed value.

Since:

0.1