Vlasov-Ampere, CPU node vs GPU node

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The same Landau damping problem on a CPU node and on a GPU node. The GPU run records how long the GPU was busy, and what it spends on copying data to it.

Tags: cpu, gpu

Runs

run	file	recorded	ranks	threads	wall time	vs baseline	files	page
CPU node	`cpu-node.h5`	2026-10-17 12:00 UTC	8	2	385 ms	baseline	2	run page
GPU node	`gpu-node.h5`	2026-10-17 12:00 UTC	4	1	89.5 ms	−76.7%	2	run page

Each run's page is linked on the right.

What changed

BaselineCandidate every run against the baseline

Durations

ShowOrder

Charts

Region durations

Grouped bars compare each region's mean call duration across the profiled runs.

Change: GPU node vs CPU node

Percent change in each region's total duration, candidate over baseline. Bars above zero got slower; a region measured in only one run leaves a gap rather than reading as a 100% change.

Rank imbalance

Each line compares a region's total duration by rank; its dashed line marks the mean across ranks. Points far from the mean identify stragglers.

Rank heatmap

This heatmap uses exclusive timings. Exclusive duration is the time spent in a region itself, excluding time spent in nested child regions; this prevents the enclosing session region from dominating the heatmap.

Metadata

commit	`0000000`
system	`synthetic`

Download run.py (715 B) View source ↗

"""Landau damping of a Langmuir wave with a Vlasov-Ampere solver: the script both runs use."""

import sys

import yaml
from scope_profiler import ProfileManager


def main(parameter_file):
    with open(parameter_file) as handle:
        parameters = yaml.safe_load(handle)
    with ProfileManager.session(label=parameters["label"]):
        with ProfileManager.region("setup"):
            state = initialise(parameters)
        for _ in range(parameters["steps"]):
            with ProfileManager.region("solve"):
                state = advance(state, parameters["dt"])
            with ProfileManager.region("exchange"):
                exchange_halos(state)


if __name__ == "__main__":
    main(sys.argv[1])