Developer Reference

  • 2020.2
  • 07/15/2020
  • Public Content
Contents

vslSkipAheadStream

Initializes a stream using the block-splitting method.

Syntax

status
=
vslskipaheadstream
(
stream
,
nskip
)
Include Files
  • mkl.fi
    ,
    mkl_vsl.f90
Input Parameters
Name
Type
Description
stream
TYPE(VSL_STREAM_STATE)
,
INTENT(IN)
Descriptor of the stream to which block-splitting method is applied
nskip
INTEGER(KIND=8)
,
INTENT(IN)
Number of skipped elements
Description
The
vslSkipAheadStream
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
vslSkipAheadStream
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 Figure
"Block-Splitting Method"
).
Block-Splitting Method
Block-Splitting Method
Block-Splitting Method
The skip-ahead method is supported only for those basic generators that allow skipping elements by the skip-ahead method, which is more efficient than simply generating them by generator with subsequent manual skipping. See VS Notes for details.
Please note that for quasi-random basic generators the skip-ahead method works with components of quasi-random vectors rather than with whole quasi-random vectors. Therefore, to skip
NS
quasi-random vectors, set the
nskip
parameter equal to the
NS*DIMEN
, where
DIMEN
is the dimension of the quasi-random vector.
If this operation results in exceeding the period of the quasi-random number generator, which is 2
32
-1, the library returns the
VSL_RNG_ERROR_QRNG_PERIOD_ELAPSED
error code.
The following code illustrates how to initialize three independent streams using the
vslSkipAheadStream
function:
Code for Block-Splitting Method
... type(VSL_STREAM_STATE) ::stream1 type(VSL_STREAM_STATE) ::stream2 type(VSL_STREAM_STATE) ::stream3 ! Creating the 1st stream status = vslnewstream(stream1, VSL_BRNG_MCG31, 174) ! Skipping ahead by 7 elements the 2nd stream status = vslcopystream(stream2, stream1); status = vslskipaheadstream(stream2, 7); ! Skipping ahead by 7 elements the 3rd stream status = vslcopystream(stream3, stream2); status = vslskipaheadstream(stream3, 7); ! 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_SKIPAHEAD_UNSUPPORTED
BRNG does not support the Skip-Ahead method.
VSL_RNG_ERROR_QRNG_PERIOD_ELAPSED
Period of the quasi-random number generator is exceeded.

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