Lightweight, measured

"Lightweight" is a claim, and claims ship with numbers. This page is the metrics table for Caliper's footprint, the script that produces every number in it, and the incumbent figures it is being compared against — with citations, because the comparison is only fair if you can check it.

The rule: no value appears here without a measurement behind it. Anything we have not measured yet says TBD — run scripts/measure_lightweight.sh, not a hopeful estimate.

The metrics table

¹ A smoke run against a debug binary (explicitly tainted as "not representative" by the script — debug Rust is typically 10–100× slower than release) measured: cold CLI→FK on a real 6-dof URDF 6.4 ms, robot load (panda) 8.0 ms, headless plan+sim peak RSS 11.5 MB, record overhead 0.43× realtime (i.e. more than 2× faster than realtime) — every one of them orders of magnitude inside its target before optimization. The release numbers replace these TBDs the first time the script runs against a release build; until then the table refuses to print them as measured.

Bit-identical determinism is not a benchmark artifact but an engine property: the core is clock-free, the one randomized component (sampling planners) uses a seeded splitmix64 PRNG, and it is pinned by tests that run on every push — the graph-executor determinism oracle (oracle/tests/test_graph.py), the seeded-planner tests, and the run-twice byte-compare the measurement script performs (seeded_plan_deterministic in its JSON output).

Reproducing the numbers

# from the repo root; build the artifacts you want measured first:
cargo build --release -p caliper-cli
maturin build --release -m crates/caliper-py/Cargo.toml   # optional: wheel size
bash scripts/measure_lightweight.sh

The script writes target/metrics/lightweight.json (machine-stamped: CPU, RAM, OS, git rev, which binary was measured) and a ready-to-paste markdown row-set (target/metrics/lightweight.md). It is honest by construction:

• artifacts that are absent are reported as skipped: <reason + how to build>, never guessed;
• pointing it at a debug binary (CALIPER_BIN=…) taints every timing with a "debug build — not representative" caveat in the provenance;
• it uses hyperfine when installed and falls back to a median-of-3 wall-clock loop when not, and says which it used;
• MEASURE_PIP=1 additionally times a pip install of the wheel into a throwaway venv (opt-in because it creates an environment).

The script has its own test suite (scripts/test_measure_lightweight.sh) — positive and negative cases per behavior, including "absent artifact must skip, not invent" and "debug override must taint".

What the incumbents cost (with citations)

These are the vendors' own published figures at the time of writing (2026-07); follow the links, they may have changed.

To be fair to the incumbents: Isaac Sim is a photorealistic GPU simulator, MoveIt is a full ROS 2 planning framework, and lerobot ships an entire training stack — they carry that weight because they do things Caliper does not (rendering-quality sim, ROS integration, GPU training). The comparison is not "Caliper does everything they do, smaller"; it is "for the load-a-robot / plan / simulate / record / deploy loop, you do not have to pay their entry price."

Related pages

• Stability contract — what these artifacts promise release over release.
• Headless CI recipe — the "runs on a free CPU runner" claim, as a copy-paste job.