Developer Reference for Intel® oneAPI Math Kernel Library - C

Developer Reference

  • 0.10
  • 10/21/2020
  • Public Content
Contents

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 2
63
. Prior calls to the function represent the number of skipped elements with array of size
n
 as shown below:
nskip
[0]+
nskip
[1]*2
64
+
nskip
[2]* 2
128
+ … +
nskip
[n-1]*2
(64*(n-1) )
;
When the number of skipped elements is less than 2
63
 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.

Product and Performance Information

1

Intel's compilers may or may not optimize to the same degree for non-Intel microprocessors for optimizations that are not unique to Intel microprocessors. These optimizations include SSE2, SSE3, and SSSE3 instruction sets and other optimizations. Intel does not guarantee the availability, functionality, or effectiveness of any optimization on microprocessors not manufactured by Intel. Microprocessor-dependent optimizations in this product are intended for use with Intel microprocessors. Certain optimizations not specific to Intel microarchitecture are reserved for Intel microprocessors. Please refer to the applicable product User and Reference Guides for more information regarding the specific instruction sets covered by this notice.

Notice revision #20110804