executor

title	Compicode Executor
emoji	🏃
colorFrom	indigo
colorTo	gray
sdk	docker
pinned	false
license	mit

CompiCode executor

The code-judging microservice behind CompiCode, written in C++17. It runs as its own Hugging Face Space; the CompiCode API sends it submissions over HTTP and gets per-testcase verdicts back.

API

Method	Route	Description
GET	/ or /health	{"ok": true, "service": "CompiCode executor"}. CompiCode pings this to wake the Space and keep it awake.
POST	/evaluate	Judge a submission (see below). Malformed bodies get 422.

POST /evaluate
{
  "code": "print(int(input()) * 2)",
  "language": "python",
  "test_cases": [{ "input": "4", "expected_output": "8" }]
}

{
  "results": [
    { "input": "4", "expected": "8", "actual": "8\n", "error": "",
      "success": true, "passed": true, "runtime_ms": 60 }
  ]
}

passed means the program exited cleanly and its output matches the expected output, ignoring leading and trailing whitespace and \r\n versus \n line endings.

How a submission is judged

1. The source is written to a fresh temporary directory and compiled once: g++ -O2 for C++, javac for Java (the file is named after the public class). Python is not compiled. The compile limit is 10 s.
2. The program runs against every testcase in parallel (EXECUTOR_WORKERS at a time, default 2, matching the Space's 2 vCPUs so busy programs don't slow each other into false timeouts).
3. Each run is a separate process in its own process group. The server feeds stdin and reads stdout/stderr through non-blocking pipes with poll(), so large inputs and outputs can't deadlock it.
4. Limits per run: 2 s wall clock (Java 3 s), 8 MB of output, 64 KB of stderr kept, 64 MB per written file, no core dumps. Over the time or output limit, the whole process group is killed. Anything a program leaves running in the background is killed when it exits.
5. A crash such as a segfault is reported as Runtime Error: Segmentation fault (signal 11).
6. The temporary directory is deleted.

The image precompiles <bits/stdc++.h> with the judge's flags, so competitive-programming C++ that includes it compiles several times faster. tini runs as PID 1 and reaps leftover processes.

Stack

• C++17, built with g++ 14 on Debian trixie
• cpp-httplib for HTTP and nlohmann/json for JSON, both from Debian packages
• POSIX fork/execvp, pipe2, poll, waitpid and setrlimit for running programs
• Runtimes judged: g++ 14 (C++), OpenJDK 21 (Java), Python 3.13

Run it locally

docker build -t compicode-executor .
docker run --rm -p 7860:7860 compicode-executor
curl -s localhost:7860/evaluate -H 'Content-Type: application/json' \
  -d '{"code":"print(input())","language":"python","test_cases":[{"input":"hi","expected_output":"hi"}]}'

Deploying

This folder is the whole Space. Copy server.cpp, Dockerfile and this README.md into the compicode-executor Space repository and push; Hugging Face rebuilds the image.