randomgen.threefry.ThreeFry.advance¶
-
ThreeFry.advance(delta, counter=
None)¶ Advance the underlying RNG as-if delta draws have occurred.
- Parameters:¶
- delta¶
Number of draws to advance the RNG. Must be less than the size state variable in the underlying RNG. delta can take any value and can be negative. Values outside 0 and 2**(N*W+N/2) are converted into this range by taking the modulo.
- counter=
None¶ Flag indicating whether the advance the counter only or both the counter and the buffer position. The default is True, which has been the pattern in in randomgen <= 1.16. This is changing to False for randomgen > 1.17. To convert between the two, use delta_new = delta * number where number is the number of elements in the generator, delta is the step size when counter=False and delta_new is the step size for counter=True
- Returns:¶
self – RNG advanced delta steps
- Return type:¶
Notes
Advancing a RNG updates the underlying RNG state as-if a given number of calls to the underlying RNG have been made. In general there is not a one-to-one relationship between the number output random values from a particular distribution and the number of draws from the core RNG. This occurs for two reasons:
The random values are simulated using a rejection-based method and so, on average, more than one value from the underlying RNG is required to generate an single draw.
The number of bits required to generate a simulated value differs from the number of bits generated by the underlying RNG. For example, two 16-bit integer values can be simulated from a single draw of a 32-bit RNG.
Advancing the RNG state resets any stored 32-bit values. If counter is False, it also resets the buffer and buffer position for backward compatibility.