difficulty and pp calculator for osu!. better, smaller, faster rewrite of https://github.com/Francesco149/oppai





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difficulty and pp calculator for osu!

this is a pure C89 rewrite of oppai with much lower memory usage, smaller and easier to read codebase executable size and better performance.

experimental taiko support is now available and appears to give correct values for actual taiko maps. converted maps are still unreliable due to incorrect slider conversion and might be completely off (use -m1 or -taiko to convert a std map to taiko).

installing (linux)

wget https://github.com/Francesco149/oppai-ng/archive/HEAD.tar.gz
tar xf HEAD.tar.gz
cd oppai-*
sudo install -Dm 755 oppai /usr/bin/oppai


you can also grab pre-compiled standalone binaries (statically linked against musl libc) from here if you are somehow too scared to run those 5 commands.

installing (windows)

download and unzip binaries from here and optionally add oppai's folder to your PATH environment variable for easy access. you can find a guide here if you don't know how.

installing (osx)

via homebrew

brew install --HEAD pmrowla/homebrew-tap/oppai-ng

Note that installing with --HEAD is recommended but not required. Installing from homebrew will place the oppai executable in your homebrew path.


Follow the same steps as for linux but substitute curl -O for wget since wget is not distributed by default in osx. The same caveat applies if you want to run the test suite - you will need to edit the download_suite script to use curl.


you can run oppai with no arguments to check the documentation.

here's some example usages:

oppai path/to/map.osu +HDHR 98% 500x 1xmiss
oppai path/to/map.osu 3x100
oppai path/to/map.osu 3x100 OD10
oppai path/to/map.osu -ojson

you can also pipe maps from standard input by setting the filename to -.

for example on linux you can do:

curl https://osu.ppy.sh/osu/774965 | oppai - +HDDT
curl https://osu.ppy.sh/osu/774965 | oppai - +HDDT 1200x 1m

while on windows it's a bit more verbose (powershell):

(New-Object System.Net.WebClient).DownloadString("https://osu.ppy.sh/osu/37658") | ./oppai -
(New-Object System.Net.WebClient).DownloadString("https://osu.ppy.sh/osu/37658") | ./oppai - +HDHR
(New-Object System.Net.WebClient).DownloadString("https://osu.ppy.sh/osu/37658") | ./oppai - +HDHR 99% 600x 1m

I got the .osu file url from "Grab latest .osu file" on the beatmap's page.

implementations for other programming languages

oppai has been implemented for many other programming languages. If you feel like making your own implementation and want it listed here, open an issue or pull request. the requirement is that it should pass the same test suite that oppai-ng passes.

bindings for other programming languages

thanks to swig it's trivial to generate native bindings for other programming languages. bindings are an interface to the C code, meaning that you get basically the same performance as C by sacrificing some portability

oppai-ng vs old oppai

executable size is around 7 times smaller:

$ cd ~/src/oppai
$ ./build.sh -static
$ wc -c oppai
574648 oppai

$ cd ~/src/oppai-ng
$ ./build -static
$ wc -c oppai
75512 oppai

oppai-ng has proper error output in whatever format you select, while legacy oppai either gives empty output or just dies with a plaintext error.

oppai-ng has well-defined errno style error codes that you can check for when using it as a library or reading its output.

the same test suite runs about 45% faster on oppai-ng compared to old oppai, also the peak resident memory size is 4 to 6 times smaller according to various time -v runs.

$ cd ~/src/oppai
$ ./build_test.sh
$ time -v ./oppai_test
    Command being timed: "./oppai_test"
    User time (seconds): 13.89
    System time (seconds): 0.10
    Percent of CPU this job got: 99%
    Elapsed (wall clock) time (h:mm:ss or m:ss): 0m 13.99s
    Average shared text size (kbytes): 0
    Average unshared data size (kbytes): 0
    Average stack size (kbytes): 0
    Average total size (kbytes): 0
    Maximum resident set size (kbytes): 45184
    Average resident set size (kbytes): 0
    Major (requiring I/O) page faults: 0
    Minor (reclaiming a frame) page faults: 2143
    Voluntary context switches: 1
    Involuntary context switches: 41
    Swaps: 0
    File system inputs: 0
    File system outputs: 0
    Socket messages sent: 0
    Socket messages received: 0
    Signals delivered: 0
    Page size (bytes): 4096
    Exit status: 0

$ cd ~/src/oppai-ng/test/
$ ./build
$ time -v ./oppai_test
    Command being timed: "./oppai_test"
    User time (seconds): 9.09
    System time (seconds): 0.06
    Percent of CPU this job got: 99%
    Elapsed (wall clock) time (h:mm:ss or m:ss): 0m 9.15s
    Average shared text size (kbytes): 0
    Average unshared data size (kbytes): 0
    Average stack size (kbytes): 0
    Average total size (kbytes): 0
    Maximum resident set size (kbytes): 11840
    Average resident set size (kbytes): 0
    Major (requiring I/O) page faults: 0
    Minor (reclaiming a frame) page faults: 304
    Voluntary context switches: 1
    Involuntary context switches: 39
    Swaps: 0
    File system inputs: 0
    File system outputs: 0
    Socket messages sent: 0
    Socket messages received: 0
    Signals delivered: 0
    Page size (bytes): 4096
    Exit status: 0

note that when the test suite is compiled without libcurl, the resident memory usage drops by a flat 4mb, so almost half of that is curl.

you can expect oppai memory usage to be under 4 mb most of the time with the raw parsed beatmap data not taking more than ~800k even for a 15 minute marathon.

the codebase has ~3-4x less lines than legacy oppai, making it easy to read and use as a single header library. not only it is smaller, but it now also implements both taiko and osu, so more features than legacy oppai.

the osu! pp and diff calc alone would be around ~3k LOC including the cli, which would be 5x less lines than legacy oppai for the same functionality.

$ cd ~/src/oppai
$ sloc *.cc

---------- Result ------------

            Physical :  15310
              Source :  14406
             Comment :  301
 Single-line comment :  289
       Block comment :  12
               Mixed :  23
               Empty :  626
               To Do :  11

Number of files read :  10


$ cd ~/src/oppai-ng
$ sloc *.c

---------- Result ------------

            Physical :  4123
              Source :  2906
             Comment :  492
 Single-line comment :  1
       Block comment :  491
               Mixed :  64
               Empty :  811
               To Do :  9

Number of files read :  2


not to mention it's C89, which will be compatible with many more platforms and old compilers than c++98

oppai.c alone is only ~2200 LOC (~1500 without comments), and you can compile piece of it out when you don't need them.

of course, it's not as heavily tested as legacy oppai (which runs 24/7 on Tillerino's back-end), however the test suite is a very good test that runs through ~12000 unique scores and I'm confident this rewrite is already very stable.

compile from source (windows)

oppai should compile even on old versions of msvc dating back to 2005, although it was only tested on msvc 2010 and higher.

have at least microsoft c++ build tools installed. visual studio with c/c++ support also works.

open a visual studio prompt:

cd path\to\oppai\source

you can also probably set up mingw and cygwin and follow the linux instructions instead, I'm not sure. I don't use windows.

using oppai as a library or making bindings

the new codebase is much easier to isolate and include in your projects.

just copy oppai.c into your project, it acts as a single-header library.

#include "../oppai.c"

int main() {
  ezpp_t ez = ezpp_new();
  ezpp_set_mods(ez, MODS_HD | MODS_DT);
  ezpp(ez, "-");
  printf("%gpp\n", ezpp_pp(ez));
  return 0;
gcc test.c
cat /path/to/file.osu | ./a.out

read oppai.c, there's documentation for each function at the top.

see examples directory for detailed examples. you can also read main.c to see how the CLI uses it.

if you don't feel comfortable writing bindings or using oppai from c code, you can use the -o parameter to output in json or other parsable formats. examples/binary.c shows how to parse the binary output.

shared library

you can also build oppai as a shared library with


this will generate a liboppai.so on linux/mac which you can copy to /usr/local/lib or anywhere in your library search paths

you can then use it by simply not defining OPPAI_IMPLEMENTATION . this will exclude all the oppai code and just leave the header part

#include "oppai.c"

int main() {
  /* ... */

then you can compile and run with

gcc test.c -lm -loppai
cat /path/to/file.osu | ./a.out

for windows you can use libbuild.bat to build (for details see the info on compiling on windows) which will generate a oppai.dll and .lib pair

and then compile your program with msvc like so

cl test.c oppai.lib

then you can simply place the dll in the same folder as your executable and run

build parameters

when you build the oppai cli, you can pass any of these parameters to the build script to disable features:

  • -DOPPAI_UTF8GRAPH use utf-8 characters for the strains graph

generating the test suite

cd test
OSU_API_KEY=... ./gentest.py  > test_suite.c

download all the maps

mkdir test_suite
cd test_suite
../download_suite.py ../test_suite.json
cd ..

the json file can be reused to avoid hitting the osu API again. keep using it unless a pp recalc happens. you don't want to keep hitting the osu api

now you can build and run the test suite:


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