Programmer Guide > OpenMP
  
OpenMP
 
This section discusses OpenMP, which is a specification for a set of compiler directives, library routines, and environment variables that can be used to specify shared memory parallelism in Fortran and C/C++ programs.
 
note
OpenMP is currently supported in PV-WAVE on Sun Solaris, Microsoft Windows, and Red Hat Enterprise Linux.
OpenMP is a hardware and software vendor supported specification designed to standardize compiler directives required to implement scalable, parallelized code for shared-memory multi-processor systems. One of the best things about OpenMP is the straightforward manner in which you can apply loop-level parallelization to sections of code in existing programs that would otherwise be unsuitable for multi-threading. This is what has been implemented for most of the array operations which take place in PV-WAVE.
To determine if a particular kernel routine supports OpenMP, look for the following logo:
at the top of the routine description within the PV-WAVE documentation. OpenMP Enabled Functionality lists the OpenMP enabled functionality of PV-WAVE. Besides the parallelized kernel routines previously listed, many Standard Library and some Math Library routines also run faster in parallel since they are built from composites of these kernel routines.
 
Table 16-1: OpenMP Enabled Functionality
ABS Function
DINDGEN Function
ACOS Function
ACOSH Function
DOUBLE Function
ADJOINT Function
EXP Function
NEIGHBORS Function
AFFINE Function
NINT Function
ALOG Function
FINDGEN Function
ALOG10 Function
FIX Function
FLOAT Function
PRODUCT Function
FLTARR Function
RBFIMSCL Procedure
ARRAYTRACE Function
REBIN Function
ASIN Function
GREAT_INT Function
REFORM Function
ASINH Function
REPLICATE Function
I32ARR Function
RESAMP
ATAN Function
I32INDGEN Function
REVERSE Function
ATANH Function
IMAGINARY Function
SIN Function
AVG Function
INDEX_CONV Function
SINH Function
BINDGEN Function
INDGEN Function
SLICE Function
BOUNDARY
INT32 Function
SMALL_INT Function
BYTARR Function
INTARR Function
SPMVM Function
BYTE Function
INTERPOL Function
SQRT Function
CINDGEN Function
INTRP Function
STDEV Function
CLUSTBOX
COMPLEX Function
LINDGEN Function
COMPLEXARR Function
LINSPACE Function
TAN Function
CONJ Function
LONARR Function
TANH Function
COS Function
LONG Function
Outer Operations
COSH Function
TOTAL Function
CPROD Function
MAKE_ARRAY Function
TRANSPOSE Function
CUMSUM Function
vecOverArr_* Functions
DBLARR Function
MAX Function
WHERE Function
DCINDGEN Function
WhereIn Function
DCOMPLEX Function
MIN Function
DCOMPLEXARR Function
 
 
PV‑WAVE provides the user with controls over the two OpenMP runtime parameters most critical to performance (see SET_OMP). These parameters are the number of threads to be used (Nthreads) and a threshold array size below which parallelization will not be considered (Threshold). Nthreads too high can degrade performance with superfluous thread overhead, and Nthreads too low can degrade performance with underused processors. The Threshold parameter prevents the overhead of a superfluous thread being created for the case Nthreads=1. The optimal values for these parameters vary depending on the hardware, operating system, mathematics, data type, and array size. Establishing these parameters for every array operation in a large PV‑WAVE application can be tedious. Fortunately PV‑WAVE can automatically vary these parameters so that they are optimal for any operation. Both the manual and the automatic methods are discussed in the following sections.
Version 2017.0
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