Documentation

RandStream.create

Create random number streams

Class

RandStream

Syntax

[s1,s2,...] = RandStream.create('gentype','NumStreams',n)
s = RandStream.create('gentype')
[ ... ] = RandStream.create('gentype', Name, Value,...)

Description

[s1,s2,...] = RandStream.create('gentype','NumStreams',n)createsnrandom number streams that use the uniform pseudorandom number generator algorithm specified bygentype. The streams are independent in a pseudorandom sense. The streams are not necessarily independent from streams created at other times.RandStream.listreturns all possible values forgentypeor seeChoosing a Random Number Generator有关创erator algorithms.

Note

Multiple streams are not supported by all generator types. Use either the multiplicative lagged Fibonacci generator (mlfg6331_64) or the combined multiple recursive generator (mrg32k3a) to create multiple streams.

s = RandStream.create('gentype')creates a single random stream. TheRandStreamconstructor is a more concise alternative when you need to create a single stream.

[ ... ] = RandStream.create('gentype', Name, Value,...)allows you to specify optional Name, Value pairs to control creation of the stream. The parameters are:

NumStreams Total number of streams of this type that will be created across sessions or labs. Default is 1.
StreamIndices Stream indices that should be created in this call. Default is1:N, whereNis the value given with the'NumStreams'parameter.
Seed Nonnegative scalar integer with which to initialize all streams. Default is 0. Seeds must be an integer between 0 and 232− 1 or'shuffle'to create a seed based on the current time.
NormalTransform Transformation algorithm used byrandn(年代,…)to generate normal pseudorandom values. Options are'Ziggurat','Polar', or'Inversion'.
CellOutput Logical flag indicating whether or not to return the stream objects as elements of a cell array. Default is false.

Typically, you callRandStream.createonce to create multiple independent streams in a single pass. Alternatively, you can create each stream from separate calls toRandStream.create, but you must specify the appropriate values forgentype,'NumStreams','Seed', and'StreamIndices'to ensure their independence:

  • Specify the same set of values forgentype,'NumStreams', and'Seed'in each case.

  • Specify a different value for'StreamIndices'that is between1and the'NumStreams'value in each case.

Examples

Create three independent streams.

[s1,s2,s3] = RandStream.create('mrg32k3a','NumStreams',3); r1 = rand(s1,100000,1); r2 = rand(s2,100000,1); r3 = rand(s3,100000,1); corrcoef([r1,r2,r3])

Create one stream from a set of three independent streams and designate it as the global stream.

s2 = RandStream.create('mrg32k3a','NumStreams',3,'StreamIndices',2); RandStream.setGlobalStream(s2);

See Also

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