README_runningtime_double_colmajor.md

Results on Running Time : Double, Column-Major

Overview : double column-major

Legend

• CPP_BLOCK 1 1 : plain C++ implementation - baseline

• NEON 8 1 : NEON with loop unrolling factor 8, single thread

• NEON 8 8 : NEON with loop unrolling factor 8, 8 threads

• BLAS 1 1 : the combination of cblas_dgemv(), vDSP_vdivD(), and vDSP_vsbmD().

Plots: Mac Mini M1 2020 8 GB

Plots: iPhone 13 mini 256 GB

Remarks on Mac Mini

• 'BLAS 1 1' shows the best overall performance. 'NEON 8 8' performs good, too.

Comparison among NEON Loop unrolling

Legend

• NEON 1 1 : NEON with no loop unrolling, single thread

• NEON 2 1 : NEON with loop unrolling factor 2, single thread

• NEON 4 1 : NEON with loop unrolling factor 4, single thread

• NEON 8 1 : NEON with loop unrolling factor 8, single thread

Plots: Mac Mini M1 2020 8 GB

Plots: iPhone 13 mini 256 GB

Remarks on Mac Mini

There is a clear benefit in using NEON intrinsics, and the explicit loop unrolling.

Comparison among NEON Multithreads

Legend

• NEON 8 1 : NEON with loop unrolling factor 8, single thread

• NEON 8 2: NEON with loop unrolling factor 8, 2 threads

• NEON 8 4: NEON with loop unrolling factor 8, 4 threads

• NEON 8 8: NEON with loop unrolling factor 8, 8 threads

Plots: Mac Mini M1 2020 8 GB

Plots: iPhone 13 mini 256 GB

Remarks on Mac Mini

There is a clear benefit in using multithreads. The overhead of synchronizing the threads is amortized around the size (512, 512).