# UniformBits

Generates integer random values with uniform bit distribution.

## Syntax

Fortran:

status = virnguniformbits( method, stream, n, r )

C:

status = viRngUniformBits( method, stream, n, r );

## Description

This function generates integer random values with uniform bit distribution.The generators of uniformly distributed numbers can be represented as recurrence relations over integer values in modular arithmetic. Apparently, each integer can be treated as a vector of several bits. In a truly random generator, these bits are random, while in pseudorandom generators this randomness can be violated. For example, a well known drawback of linear congruential generators is that lower bits are less random than higher bits (for example, see [Knuth81]). For this reason, care should be taken when using this function. Typically, in a 32-bit LCG only 24 higher bits of an integer value can be considered random. See VSL Notes for details.

## Input Parameters

Name | Type | Description
--- | --- | ---
method | FORTRAN: INTEGER, INTENT(IN) C: int | Generation method; dummy and set to 0. The specific value is as follows: `VSL_METHOD_IUNIFORMBITS_STD` Standard method. Currently there is only one method for this distribution generator.
stream | FORTRAN: TYPE (VSL_STREAM_STATE), INTENT(IN) C: VSLStreamStatePtr | FORTRAN: Descriptor of the stream state structure. C: Pointer to the stream state structure
n | FORTRAN: INTEGER, INTENT(IN) C: int | Number of random values to be generated

## Output Parameters

Name | Type | Description
--- | --- | ---
r | FORTRAN: INTEGER, INTENT(OUT) C: unsigned int* | FORTRAN: Vector of n random integer numbers. If the stream was generated by a 64 or a 128-bit generator, each integer value is represented by two or four elements of r respectively. The number of bytes occupied by each integer is contained in the field wordsize of the structure VSL_BRNG_PROPERTIES. The total number of bits that are actually used to store the value are contained in the field nbits of the same structure. See Advanced Service Routines for a more detailed discussion of VSLBRngProperties. C: Vector of n random integer numbers. If the stream was generated by a 64 or a 128-bit generator, each integer value is represented by two or four elements of r respectively. The number of bytes occupied by each integer is contained in the field WordSize of the structure VSLBRngProperties. The total number of bits that are actually used to store the value are contained in the field NBits of the same structure.See Advanced Service Routines for a more detailed discussion of VSLBRngProperties.

## Return Values

VSL_ERROR_OK, VSL_STATUS_OK
  Indicates no error, execution is successful.
VSL_ERROR_NULL_PTR
  stream is a NULL pointer.
VSL_ERROR_BAD_STREAM

  stream is not a valid random stream.

VSL_ERROR_BAD_UPDATE

  Callback function for an abstract BRNG returns an invalid number of updated entries in a buffer, that is, `< 0` or `> nmax`.

VSL_ERROR_NO_NUMBERS

  Callback function for an abstract BRNG returns 0 as the number of updated entries in a buffer.

Parent topic: Discrete Distributions