puzzlef / vector-multiplication-openmp Goto Github PK

Comparing performance of sequential vs OpenMP-based element-by-element vector multiplication.

In each of the experiments given below, we multiply two floating-point vectors x and y, with number of elements from 10^6 to 10^9 using OpenMP. Each element count is attempted with various approaches, running each approach 5 times to get a good time measure. Multiplication here represents any memory-aligned independent operation, or a map() operation.

In this experiment (adjust-schedule), we multiply two floating-point vectors x and y using OpenMP. Each element count is attempted with various OpenMP schedule configs. Results indicate a schedule-kind of auto to be suitable.

In this experiment (compare-sequential, main), we compare the performance between finding x*y using a single thread (sequential), and using OpenMP. Here x, y are both floating-point vectors, and the comparison in performed on a number of vector sizes. Note that neither approach makes use of SIMD instructions which are available on all modern hardware. While it might seem that OpenMP method would be a clear winner, the results indicate it is not the case. This is possibly because of high communication costs, and not enough computational workload as indicated by this answer. However, from 10⁸ elements, OpenMP approach performs better than sequential. All outputs are saved in gist. Some charts are also included below, generated from sheets.

• open MP - dot product
• What's the difference between “static” and “dynamic” schedule in OpenMP?
• Git pulling a branch from another repository?