{"action":"created","issue":{"url":"https://api.github.com/repos/lz4/lz4/issues/174","repository_url":"https://api.github.com/repos/lz4/lz4","labels_url":"https://api.github.com/repos/lz4/lz4/issues/174/labels{/name}","comments_url":"https://api.github.com/repos/lz4/lz4/issues/174/comments","events_url":"https://api.github.com/repos/lz4/lz4/issues/174/events","html_url":"https://github.com/lz4/lz4/issues/174","id":123182216,"number":174,"title":"Performance degradation during 2 years of LZ4 development","user":{"login":"kirillx","id":8434623,"avatar_url":"https://avatars.githubusercontent.com/u/8434623?v=3","gravatar_id":"","url":"https://api.github.com/users/kirillx","html_url":"https://github.com/kirillx","followers_url":"https://api.github.com/users/kirillx/followers","following_url":"https://api.github.com/users/kirillx/following{/other_user}","gists_url":"https://api.github.com/users/kirillx/gists{/gist_id}","starred_url":"https://api.github.com/users/kirillx/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/kirillx/subscriptions","organizations_url":"https://api.github.com/users/kirillx/orgs","repos_url":"https://api.github.com/users/kirillx/repos","events_url":"https://api.github.com/users/kirillx/events{/privacy}","received_events_url":"https://api.github.com/users/kirillx/received_events","type":"User","site_admin":false},"labels":[],"state":"closed","locked":false,"assignee":null,"assignees":[],"milestone":null,"comments":14,"created_at":"2015-12-20T20:52:18Z","updated_at":"2016-11-11T00:32:42Z","closed_at":"2016-11-11T00:32:42Z","body":"I previously used LZ4 version from April 2, 2013.\nJust updated LZ4 in my sources with latest version (r131) and during compatibility testing found degradation in compression speed (compatibility was confirmed though). On my test text file ~400MB in size new version takes ~1.9sec to compress, while the old one took only ~1.13sec (70% slower!). This is pure compression speed, w/o any I/O as file is fully cached.\n\nAny ideas what has happened with the fastest compression algorithm?\n\nMachine: MacBookPro 2013, 2.3 GHz Intel Core i7\nOS: Linux CentOS 7.1 x64\n"},"comment":{"url":"https://api.github.com/repos/lz4/lz4/issues/comments/259849322","html_url":"https://github.com/lz4/lz4/issues/174#issuecomment-259849322","issue_url":"https://api.github.com/repos/lz4/lz4/issues/174","id":259849322,"user":{"login":"Cyan4973","id":750081,"avatar_url":"https://avatars.githubusercontent.com/u/750081?v=3","gravatar_id":"","url":"https://api.github.com/users/Cyan4973","html_url":"https://github.com/Cyan4973","followers_url":"https://api.github.com/users/Cyan4973/followers","following_url":"https://api.github.com/users/Cyan4973/following{/other_user}","gists_url":"https://api.github.com/users/Cyan4973/gists{/gist_id}","starred_url":"https://api.github.com/users/Cyan4973/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/Cyan4973/subscriptions","organizations_url":"https://api.github.com/users/Cyan4973/orgs","repos_url":"https://api.github.com/users/Cyan4973/repos","events_url":"https://api.github.com/users/Cyan4973/events{/privacy}","received_events_url":"https://api.github.com/users/Cyan4973/received_events","type":"User","site_admin":false},"created_at":"2016-11-11T00:32:42Z","updated_at":"2016-11-11T00:32:42Z","body":"I made some tests at `-O2` setting, comparing previous speed champion `r117` with newest `dev` version, below called `v1.7.2`, on a Mac laptop. The results are rather favorable : \r\n\r\n| Version |   compiler              | setting | C.Speed  | D.Speed |\r\n| ------- | ------------------ | ------- | --------   | --------- |\r\n|  r117     |  Apple LLVM 8.0.0 |  -O2    | 463 MB/s | 1.2 GB/s |\r\n|  v1.7.2  |  Apple LLVM 8.0.0 |  -O2    | 495 MB/s | 2.4 GB/s |\r\n|  r117     |  Apple LLVM 8.0.0 |  -O3    | 465 MB/s | 1.2 GB/s |\r\n|  v1.7.2  |  Apple LLVM 8.0.0 |  -O3    | 495 MB/s | 2.4 GB/s |\r\n|  r117     |  gcc 6.2.0               |  -O2    | 461 MB/s | 2.1 GB/s |\r\n|  v1.7.2  |  gcc 6.2.0               |  -O2    | 500 MB/s | 2.5 GB/s |\r\n|  r117     |  gcc 6.2.0               |  -O3    | 463 MB/s | 2.1 GB/s |\r\n|  v1.7.2  |  gcc 6.2.0               |  -O3    | 505 MB/s | 2.5 GB/s |\r\n\r\nDifferences between `-O2` and `-O3` is negligible, and newer version is faster.\r\n\r\nOn a different desktop PC machine (hence not comparable to above results) : \r\n\r\n| Version |   compiler              | setting | C.Speed  | D.Speed |\r\n| ------- | ------------------ | ------- | --------   | --------- |\r\n|  r117     |  gcc 4.8.5               |  -O2    | 579 MB/s | 2.6 GB/s |\r\n|  v1.7.2  |  gcc 4.8.5               |  -O2    | __592 MB/s__ | __2.4 GB/s__ |\r\n|  r117     |  gcc 4.8.5               |  -O3    | 579 MB/s | 2.6 GB/s |\r\n|  v1.7.2  |  gcc 4.8.5               |  -O3    | __619 MB/s__ | __3.2 GB/s__ |\r\n\r\nIn this case, speed difference between `-O2` and `-O3` is measurable.\r\nIt seems the reason could be attributed to the older compiler version.\r\nSo let's try a newer compiler version on same machine : \r\n\r\n| Version |   compiler              | setting | C.Speed  | D.Speed |\r\n| ------- | ------------------ | ------- | --------   | --------- |\r\n|  r117     |  gcc 5.4.1               |  -O2    | 583 MB/s | 2.5 GB/s |\r\n| v1.7.2   |  gcc 5.4.1               |  -O2    | 616 MB/s | 3.2 GB/s |\r\n|  r117     |  gcc 5.4.1               |  -O3    | 583 MB/s | 2.5 GB/s |\r\n| v1.7.2   |  gcc 5.4.1               |  -O3    | 621 MB/s | 3.2 GB/s |\r\n\r\nAnd indeed, with a more recent version, differences between `-O2` and `-O3` disappear.\r\n\r\nSo it seems the problem of reduced performance at `-O2` setting is specific to gcc 4.x serie.\r\nIt also seems that newer `dev` version remains nonetheless competitive compared to `r117` even at `-O2` setting and even on gcc 4.8.x."}}
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