Opp repl comparing simulations

Skill tabgab/opp_repl-skill/opp-repl-comparing-simulations

Composable Anthropic-format Agent Skills for driving OMNeT++ simulations via opp_repl. Works in Claude, Windsurf, and any SKILL.md-aware agent.

Install

npx -y skills add tabgab/opp_repl-skill --skill opp-repl-comparing-simulations

Assembled from the repository path, not quoted from the project. Check it against their README if it does not work.

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What its author says it does

Copied from the file, not written here

Compare simulation results between two projects or two git commits using opp_repl. compare_simulations / compare_simulations_between_commits check stdout trajectories, fingerprint trajectories, and scalar results; report IDENTICAL/DIVERGENT/DIFFERENT; and support debug_at_fingerprint_divergence_position() for interactive bisection. Load when investigating a regression or validating a refactor.

SKILL.md

3.7 KB, as published. Nobody here has run it

Comparing simulations

Run the same configuration against two project variants — two checked-out projects, two git commits, or a project and an overlay build — then diff the results at three levels.

Upstream reference: https://github.com/omnetpp/opp_repl/blob/main/doc/comparing_simulations.md

What gets compared

Layer	Verdict
Stdout trajectory	IDENTICAL / DIVERGENT
Fingerprint trajectory	IDENTICAL / DIVERGENT
Scalar statistical result	IDENTICAL / DIFFERENT

The overall CompareSimulationsTaskResult code is the worst-case across the three. IDENTICAL means every byte and value matches; DIVERGENT marks a point in the event stream where the two runs first disagree; DIFFERENT means only the scalar summary differs (within/outside tolerance).

Comparing two projects

r = compare_simulations(
    simulation_project_1=inet_project,
    simulation_project_2=inet_baseline_project,
    working_directory_filter="examples/ethernet",
    config_filter="General",
    run_number=0)

Comparing two git commits of the same project

r = compare_simulations_between_commits(
    inet_project, "HEAD~1", "HEAD",
    config_filter="General",
    run_number=0)

Internally this uses git worktrees / overlay builds so you don't have to check out the other commit manually.

Drilling into a result

first = r.results[0]
first.stdout_trajectory_comparison_result       # IDENTICAL / DIVERGENT
first.fingerprint_trajectory_comparison_result  # IDENTICAL / DIVERGENT
first.statistical_comparison_result             # IDENTICAL / DIFFERENT

first.print_different_statistical_results(include_relative_errors=True)

# Interactive debugging at the divergence point
first.debug_at_fingerprint_divergence_position()
first.show_divergence_position_in_sequence_chart()

Typical workflow

Noticed a fingerprint test regression in INET's examples/ethernet.

Compare HEAD vs. the last-known-good tag:

r = compare_simulations_between_commits(
    inet_project, "v4.5", "HEAD",
    working_directory_filter="examples/ethernet",
    config_filter="General", run_number=0)

r.results[0].show_divergence_position_in_sequence_chart() to see the event where the two runs diverge.
.debug_at_fingerprint_divergence_position() launches a debug session at that event on both sides.

Pitfalls

Non-deterministic simulations flap as DIVERGENT even when "the same". Fix the seed / RNG before comparing.
Two projects must have matching config names and a matching INI file in the working directory — otherwise the comparison SKIPs.
compare_simulations_between_commits() uses git worktrees under the hood. A very dirty working tree (untracked build products) can confuse the worktree build; commit or stash first.
Statistical tolerances differ per project. For cross-project comparisons, understand each statistics_folder convention.