BlockRandom

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`BlockRandom`

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BlockRandom[expr]

evaluates expr with all pseudorandom generators localized, so that uses of SeedRandom, RandomInteger, and related functions within the evaluation of expr do not affect subsequent pseudorandom sequences.

Details and Options

BlockRandom[expr] in effect saves the states of all pseudorandom generators before evaluating expr, then restores them afterwards.
BlockRandom[expr] always gives the same result as just evaluating expr, though it can affect values obtained for subsequent expressions.
BlockRandom[expr,RandomSeeding->seeding] specifies that the random generators should be seeded with the specified seeding before evaluating expr.
BlockRandom has attribute HoldFirst.
Many built-in functions in the Wolfram Language effectively use BlockRandom.

Examples

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Basic Examples (2)Summary of the most common use cases

Use BlockRandom to localize the use of a pseudorandom generator:

In[1]:=1

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https://wolfram.com/xid/0rtadeduu-cs

Out[1]=1

Use BlockRandom to prevent one use of a randomized algorithm from affecting others:

In[1]:=1

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https://wolfram.com/xid/0rtadeduu-sw2

Out[1]=1

In[2]:=2

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https://wolfram.com/xid/0rtadeduu-fue

Out[2]=2

Scope (1)Survey of the scope of standard use cases

BlockRandom works with all pseudorandom generators in the Wolfram Language:

In[1]:=1

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https://wolfram.com/xid/0rtadeduu-dlz

Out[1]=1

In[2]:=2

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https://wolfram.com/xid/0rtadeduu-fpk

Out[2]=2

Options (3)Common values & functionality for each option

RandomSeeding (3)

Use a particular random seed to ensure predictable results:

In[1]:=1

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https://wolfram.com/xid/0rtadeduu-b4pm67

Out[1]=1

In[2]:=2

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https://wolfram.com/xid/0rtadeduu-ga4rgy

Out[2]=2

When a generator is used outside BlockRandom, the results without seeding are changed:

In[3]:=3

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https://wolfram.com/xid/0rtadeduu-fjf73s

Out[3]=3

In[4]:=4

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https://wolfram.com/xid/0rtadeduu-j9glhv

Out[4]=4

In[5]:=5

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https://wolfram.com/xid/0rtadeduu-etyzfp

Out[5]=5

Use a RandomGeneratorState object to simultaneously specify the seed and method:

In[1]:=1

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https://wolfram.com/xid/0rtadeduu-0tmjou

Out[1]=1

Use Automatic seeding to get different results every time:

In[1]:=1

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https://wolfram.com/xid/0rtadeduu-jui22b

Out[1]=1

In[2]:=2

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https://wolfram.com/xid/0rtadeduu-dnd6p4

Out[2]=2

Applications (2)Sample problems that can be solved with this function

Run a randomized algorithm without affecting other random sequences:

In[1]:=1

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https://wolfram.com/xid/0rtadeduu-gwl

Out[1]=1

In[2]:=2

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https://wolfram.com/xid/0rtadeduu-v1w

Compute a Monte Carlo approximation to :

In[3]:=3

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https://wolfram.com/xid/0rtadeduu-bb

Out[3]=3

BlockRandom prevents other random sequences from being affected:

In[4]:=4

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https://wolfram.com/xid/0rtadeduu-tl3

Out[4]=4

Get the "same" random number at different precisions:

In[1]:=1

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https://wolfram.com/xid/0rtadeduu-tls

Out[1]=1

Properties & Relations (1)Properties of the function, and connections to other functions

BlockRandom effectively does the same as resetting the random seed to its previous value:

In[2]:=2

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https://wolfram.com/xid/0rtadeduu-llu

Out[1]=1

In[2]:=2

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https://wolfram.com/xid/0rtadeduu-txb

Out[2]=2

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