ESPResSo
ESPResSo is a soft-matter molecular-dynamics package for coarse-grained models — polymers, colloids, and charged fluids — with P3M (Particle–Particle Particle–Mesh) electrostatics. On the Orange Pi RV2 we A/B double-precision libfftw3.so.3 under one unchanged pypresso binary via LD_PRELOAD.
Benchmark source: opensolvers/benchmarks/espresso. Companion FFT probes: FFTW, GROMACS, ScaFaCoS.
Change one variable. Same ESPResSo / OpenBLAS (scalar pinned); only FFTW scalar vs r5v differs. Check
E_coul/E_totbefore trusting wall time.
Bottom line: RVV FFTW wins a modest ~1.12× on the timed MD segment — same ballpark as GROMACS PME 3D-FFT (~1.14–1.23×), diluted by real-space LJ/Coulomb, thermostat, and P3M spread/gather.
Setup
| Piece | Value |
|---|---|
| Board | Orange Pi RV2 · SpaceMiT X60 |
| ESPResSo | EESSI ESPResSo/4.2.2-foss-2025b |
| Workload | charged WCA/LJ fluid · N=512 · box=20 · 200 timed steps · 1 thread |
| Axis | LD_PRELOAD scalar vs r5v libfftw3.so.3 |
Results (2026-08-21)
| Backend | Wall (integrator) | E_coul | E_tot |
|---|---|---|---|
scalar libfftw3 |
2.706 s | −98.404639 | 632.452568 |
r5v (RVV) libfftw3 |
2.425 s | −98.404669 | 632.452480 |
| speedup | 1.12× | Δ ~3e−5 | Δ ~9e−5 |
Energies match across backends.
Measured: 2026-08-21 on Orange Pi RV2.