cpg vs oj + oj-prepare

online-judge-tools/oj and online-judge-tools/template-generator (which provides oj-prepare) are well-known tools for competitive programming. I've used them for a long time, but wanted a more integrated workflow for managing workspaces, compiling solutions, and checking submissions, so I created cpg.

What changes with cpg

Runs as a native Rust executable, so it's very easy to install and update.
- The experimental oj backend uses uv and a managed Python virtual environment.
Places problems and contests under a fixed root directory.
- So you don't have to care where to download problems. (and potentially lower a hurdle for solving problems)
Prefixes contest problem directories with indexes.
- Useful for virtual contests and Yukicoder contests, where problems are not ordered by ID.
Shares workspace templates between single problems and contests.
Compiles and tests a source file in one command, using configured language commands and build profiles.
- In addition to running solutions, preprocess and presubmit hooks can transform source files before testing or submission.
cpg results --ui monitors your submissions, including those made in the browser.
- So you don't have to open submission pages.

Command equivalents

These examples use the oj commands and oj-prepare. For cpg commands that take a source file, configure the language's compile/run commands first. Direct commands after -- do not require language settings.

Task	oj / oj-prepare	cpg
Download a problem's samples	`oj download URL`	`cpg download URL`
Prepare a contest or a problem	`oj-prepare URL`	`cpg prepare URL`
Compile and test C++	`g++ solution.cpp -o solution && oj test -c ./solution`	`cpg test solution.cpp`¹
Test a Ruby command	`oj test -c "ruby solution.rb"`	`cpg test solution.rb`
Run test against specific input file	`oj test -c "ruby solution.rb" test/sample-1.in`	`cpg test --input-path ./test/sample-1.in solution.rb`
Generate inputs in `test/`	`oj generate-input "ruby random.rb"`	`cpg generate random.rb`²
Generate missing answers in `test/`	`oj generate-output -c "ruby naive.rb"`	`cpg generate --answer naive.rb`
Run an interactive judge	`oj test-reactive -c "ruby solution.rb" "ruby judge.rb"`	`cpg test --interactive --judge "judge.rb" solution.rb`
Submit to an explicit problem	`oj submit URL solution.cpp`	`cpg submit solution.cpp --problem URL`

While cpg supports compiling and testing a source file in one command, you can still specify a command to run directly (cpg test -- ruby solution.rb) or compile first and then test (g++ solution.cpp -o solution && cpg test ./solution).
cpg generates random cases in the random/ directory by default, but you can use --test-dir to specify a different location, including test/.

Differences when switching

Command line options are different. See cpg commands for details.
There are no template system for template files. cpg copies template files as they are.
No oj-template equivalent.
No oj downlload --system equivalent.

Migrating templates

cpg init detects prepare.config.toml in the XDG configuration directory for online-judge-tools and asks whether to import its [templates] entries. The import copies referenced local files into problem_template.

After importing, add language settings and import browser cookies. Move shared project files into workspace_template if they should live at the contest root.

Existing oj workspaces are not converted, but their .in and .out files can be used directly for local testing:

cpg test --test-dir ./test -- ruby ./solution.rb

Submission from a directory without .cpg.toml requires --problem URL.