vslSkipAheadStreamEx

Developer Reference for Intel® oneAPI Math Kernel Library for C

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ID 766684

Date 12/16/2022

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vslSkipAheadStreamEx

Initializes a stream using the block-splitting method with partitioned number of skipped elements.

Syntax

status = vslSkipAheadStreamEx( stream, n, nskip);

Include Files

mkl.h

Input Parameters

Name	Type	Description
stream	VSLStreamStatePtr	Pointer to the stream state structure to which block-splitting method is applied
n	const MKL_INT	Number of summands in nskip
nskip	const MKL_UINT64[]	Partitioned number of skipped elements

Description

The vslSkipAheadStreamEx function skips a given number of elements in a random stream. This feature is particularly useful in distributing random numbers from original random stream across different computational nodes. If the largest number of random numbers used by a computational node is nskip, then the original random sequence may be split by vslSkipAheadStreamEx into non-overlapping blocks of nskip size so that each block corresponds to the respective computational node. The number of computational nodes is unlimited. This method is known as the block-splitting method or as the skip-ahead method. See Notes for Intel® MKL Vector Statisticsfor more details.

Use this function when the number of elements to skip in a random stream is greater than 2⁶³. Prior calls to the function represent the number of skipped elements with array of size n as shown below:

nskip[0]+ nskip[1]*2⁶⁴+nskip[2]* 2¹²⁸+ … +nskip[n-1]*2^{(64*(n-1) )};

When the number of skipped elements is less than 2⁶³ you can use either vslSkipAheadtreamEx or vslSkipAheadStream. The following code illustrates how to initialize three independent streams using the vslSkipAheadStreamEx function:

VSLStreamStatePtr stream1; VSLStreamStatePtr stream2; VSLStreamStatePtr stream3;

/* Creating the 1st stream
*/
status = vslNewStream(&stream1, VSL_BRNG_MCG31, 174);

/* To skip 2^64 elements in the random stream SkipAheadStreamEx(nskip) function should be called with nskip represented as nskip = 2^64 = 0 + 1 * 2^64
*/
MKL_UINT64 nskip[2];
nskip[0]=0;
nskip[1]=1;

/* Skipping ahead by 2^64 elements the 2nd stream
/*
status = vslCopyStream(&stream2, stream1); 
status = vslSkipAheadStreamEx (stream2, 2, nskip);

/* Skipping ahead by 2^64 elements the 3rd stream
/*
status = vslCopyStream(&stream3, stream2); 
status = vslSkipAheadStreamEx (stream3, 2, nskip);

/* Generating random numbers
*/
...
/* Deleting the streams
*/
status = vslDeleteStream(&stream1);
status = vslDeleteStream(&stream2);
status = vslDeleteStream(&stream3);
...

Return Values

VSL_ERROR_OK, VSL_STATUS_OK: Indicates no error, execution is successful.
VSL_ERROR_NULL_PTR: stream is a NULL pointer.
VSL_RNG_ERROR_BAD_STREAM: stream is not a valid random stream.
VSL_RNG_ERROR_SKIPAHEADEX_UNSUPPORTED: BRNG does not support the advanced Skip-Ahead method.

Parent topic: Service Routines

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Developer Reference for Intel® oneAPI Math Kernel Library for C

vslSkipAheadStreamEx