{"id":21804920,"url":"https://github.com/pez/ghost-chase-condition","last_synced_at":"2026-05-06T17:35:40.339Z","repository":{"id":66560130,"uuid":"454352114","full_name":"PEZ/ghost-chase-condition","owner":"PEZ","description":"Chasing a performance-eating ghost down the JVM rabbit hole","archived":false,"fork":false,"pushed_at":"2022-02-10T07:58:30.000Z","size":29,"stargazers_count":2,"open_issues_count":0,"forks_count":0,"subscribers_count":2,"default_branch":"master","last_synced_at":"2025-03-21T07:41:39.259Z","etag":null,"topics":["clojure","java","jvm","performance","sieve-of-eratosthenes"],"latest_commit_sha":null,"homepage":"","language":"Java","has_issues":true,"has_wiki":null,"has_pages":null,"mirror_url":null,"source_name":null,"license":"mit","status":null,"scm":"git","pull_requests_enabled":true,"icon_url":"https://github.com/PEZ.png","metadata":{"files":{"readme":"README.md","changelog":null,"contributing":null,"funding":null,"license":"LICENSE","code_of_conduct":null,"threat_model":null,"audit":null,"citation":null,"codeowners":null,"security":null,"support":null,"governance":null,"roadmap":null,"authors":null,"dei":null,"publiccode":null,"codemeta":null}},"created_at":"2022-02-01T10:55:59.000Z","updated_at":"2022-02-06T18:44:35.000Z","dependencies_parsed_at":"2023-02-28T20:15:42.142Z","dependency_job_id":null,"html_url":"https://github.com/PEZ/ghost-chase-condition","commit_stats":null,"previous_names":[],"tags_count":0,"template":false,"template_full_name":null,"purl":"pkg:github/PEZ/ghost-chase-condition","repository_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub/repositories/PEZ%2Fghost-chase-condition","tags_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub/repositories/PEZ%2Fghost-chase-condition/tags","releases_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub/repositories/PEZ%2Fghost-chase-condition/releases","manifests_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub/repositories/PEZ%2Fghost-chase-condition/manifests","owner_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub/owners/PEZ","download_url":"https://codeload.github.com/PEZ/ghost-chase-condition/tar.gz/refs/heads/master","sbom_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub/repositories/PEZ%2Fghost-chase-condition/sbom","scorecard":null,"host":{"name":"GitHub","url":"https://github.com","kind":"github","repositories_count":286080680,"owners_count":32704683,"icon_url":"https://github.com/github.png","version":null,"created_at":"2022-05-30T11:31:42.601Z","updated_at":"2026-05-06T08:33:17.875Z","status":"ssl_error","status_checked_at":"2026-05-06T08:33:17.221Z","response_time":117,"last_error":"SSL_connect returned=1 errno=0 peeraddr=140.82.121.6:443 state=error: unexpected eof while reading","robots_txt_status":"success","robots_txt_updated_at":"2025-07-24T06:49:26.215Z","robots_txt_url":"https://github.com/robots.txt","online":false,"can_crawl_api":true,"host_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub","repositories_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub/repositories","repository_names_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub/repository_names","owners_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub/owners"}},"keywords":["clojure","java","jvm","performance","sieve-of-eratosthenes"],"created_at":"2024-11-27T11:57:25.982Z","updated_at":"2026-05-06T17:35:40.321Z","avatar_url":"https://github.com/PEZ.png","language":"Java","funding_links":[],"categories":[],"sub_categories":[],"readme":"# ghost-chase-condition\n\nFollowing a performance-eating ghost down the JVM rabbit hole.\n\nPlease see [this blog post](https://blog.agical.se/en/posts/java-bitset-performance-mystery) for an introduction to the mystery.\n\nTL;DR: The same `javac` compiled program runs at two different speeds: 1X and 0.5X, on the same machine, using Docker. I've managed to create a somewhat minimal repro.\n\nTo run the repro:\n\n```\ndocker build -t primes-java-bitset  . \u0026\u0026 docker run --rm -it primes-java-bitset\n```\n\nSample output on [this machine](machine-pez-x64-ubuntu.md):\n\n```\n0 - Passes: 2767, count: 78498, Valid: true\n1 - Passes: 2751, count: 78498, Valid: true\n2 - Passes: 2766, count: 78498, Valid: true\n3 - Passes: 2756, count: 78498, Valid: true\n4 - Passes: 6049, count: 78498, Valid: true\n5 - Passes: 2763, count: 78498, Valid: true\n6 - Passes: 2765, count: 78498, Valid: true\n7 - Passes: 2760, count: 78498, Valid: true\n8 - Passes: 6043, count: 78498, Valid: true\n9 - Passes: 2760, count: 78498, Valid: true\n```\n\nI'm getting some good help over at HN: https://news.ycombinator.com/item?id=30226083","project_url":"https://awesome.ecosyste.ms/api/v1/projects/github.com%2Fpez%2Fghost-chase-condition","html_url":"https://awesome.ecosyste.ms/projects/github.com%2Fpez%2Fghost-chase-condition","lists_url":"https://awesome.ecosyste.ms/api/v1/projects/github.com%2Fpez%2Fghost-chase-condition/lists"}