One of my recent tasks is to parallelize a fairly large program in Fortran 90. The subroutine I am targeting spends a great time doing a computationally extensive loop. I have tried the following:
!$OMP PARALLEL DO DEFAULT(PRIVATE) SHARED (array2D_1, array2D_2, .., scalar1, scalar2,.., scalarN)
<the calculations >
!$OMP END PARALLEL DO
This article describes a parallel merge sort code, and why it is more scalable than parallel quicksort or parallel samplesort. The code relies on the C++11 “move” semantics. It also points out a scalability trap to watch out for with C++. The attached code has implementations in Intel® Threading Building Blocks (Intel® TBB), Intel® Cilk™ Plus, and OpenMP*.
This article provides a recipe for compiling and running the Hogbom Clean benchmark for the Intel® Xeon Phi™ coprocessor and discusses the various optimizations applied to the code.
For the next optimization, I knew what I wanted to do; I just didn’t know what to call it. In looking for words that describes loosely-synchronous, I came across plesiochronous:
In telecommunications, a plesiochronous system is one where different parts of the system are almost, but not quite, perfectly synchronized.
The prior part (3) of this blog showed the effects of the first-level implementation of the Hyper-Thread Phalanx. The change in programming yielded 9.7% improvement in performance for the small model, and little to no improvement in the large model. This left part 3 of this blog with the questions:
What is non-optimal about this strategy?
And: What can be improved?
There are two things, one is obvious, and the other is not so obvious.
I'm trying to build the openmprtl on Mac OS X 10.9, to be used with OpenMP/Clang project. Is this supposed to be possible? A new thing with 10.9 is that gcc is just a macro for clang, which maybe is confusing the build scripts.
I try to build with:
And I get a build error in check-tools.pl "Cannot parse GNU compiler version" as it has run gcc and get clang output (as gcc is just a macro for clang on 10.9). I was thinking that when you compile with "compiler=clang" the check-tools.pl would not look for gcc at all.
I'm trying to scale a for loop but I'm getting even worse results.
My serial code runs in 30s but my openmp version completed in 200s.
This is my pragma.
int procs = omp_get_num_procs(); #pragma omp parallel for num_threads(procs)\ shared (c, u, v, w, k, j, i, nx, ny) \ reduction(+: a, b, c, d, e, f, g, h, i)
And this are my openmp exports :
export OMP_NUM_THREADS=5 export KMP_AFFINITY=verbose,scatter
And this is my verbose running in 1 node 8 cores
The prior part (2) of this blog provided a header and set of function that can be used to determine the logical core and logical Hyper-Thread number within the core. This determination is to be use in an optimization strategy called the Hyper-Thread Phalanx.
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