# Geometric

Generates geometrically distributed random values.

## Syntax

Fortran:

status = virnggeometric( method, stream, n, r, p )

C:

status = viRngGeometric( method, stream, n, r, p );

## Description

This function generates geometrically distributed random numbers with probability p of a single trial success, where `p∈R; 0 < p < 1.`

A geometrically distributed variate represents the number of independent Bernoulli trials preceding the first success. The probability of a single Bernoulli trial success is p.

The probability distribution is given by:

P(X = k) = p·(1 - p)k, k∈ {0,1,2, ... }.

The cumulative distribution function is as follows:

## Input Parameters

Name | Type | Description
--- | --- | ---
method | FORTRAN: INTEGER, INTENT(IN) C: int | Generation method. The specific value is as follows: `VSL_METHOD_IGEOMETRIC_ICDF` Inverse cumulative distribution function method.
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
p | FORTRAN: DOUBLE PRECISION, INTENT(IN) C: double | Success probability p of a trial

## Output Parameters

Name | Type | Description
--- | --- | ---
r | FORTRAN: INTEGER, INTENT(OUT) C: int* | Vector of n geometrically distributed random values

## 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