OpenBLAS/README.md

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# OpenBLAS
## Introduction
OpenBLAS is an optimized BLAS library based on GotoBLAS2 1.13 BSD version. OpenBLAS is an open source project supported by Lab of Parallel Software and Computational Science, ISCAS <http://www.rdcps.ac.cn>.
Please read the documents on OpenBLAS wiki pages <http://github.com/xianyi/OpenBLAS/wiki>.
## Installation
Download from project homepage. http://xianyi.github.com/OpenBLAS/
Or, check out codes from git://github.com/xianyi/OpenBLAS.git
### Normal compile
* type "make" to detect the CPU automatically.
or
* type "make TARGET=xxx" to set target CPU, e.g. "make TARGET=NEHALEM". The full target list is in file TargetList.txt.
### Cross compile
Please set CC and FC with the cross toolchains. Then, set HOSTCC with your host C compiler. At last, set TARGET explicitly.
Examples:
On X86 box, compile this library for loongson3a CPU.
make BINARY=64 CC=mips64el-unknown-linux-gnu-gcc FC=mips64el-unknown-linux-gnu-gfortran HOSTCC=gcc TARGET=LOONGSON3A
### Debug version
make DEBUG=1
### Intall to the directory (Optional)
Example:
make install PREFIX=your_installation_directory
The default directory is /opt/OpenBLAS
## Support CPU & OS
Please read GotoBLAS_01Readme.txt
### Additional support CPU:
#### x86/x86-64:
- **Intel Xeon 56xx (Westmere)**: Used GotoBLAS2 Nehalem codes.
- **Intel Sandy Bridge**: Optimized Level-3 BLAS with AVX on x86-64.
- **AMD Bobcat**: Used GotoBLAS2 Barcelona codes.
- **AMD Bulldozer**: Used GotoBLAS2 Barcelona codes.
#### MIPS64:
- **ICT Loongson 3A**: Optimized Level-3 BLAS and the part of Level-1,2.
- **ICT Loongson 3B**: Experimental
### Support OS:
- **GNU/Linux**
- **MingWin/Windows**: Please read <https://github.com/xianyi/OpenBLAS/wiki/How-to-use-OpenBLAS-in-Microsoft-Visual-Studio>.
- **Darwin/Mac OS X**: Experimental. Although GotoBLAS2 supports Darwin, we are the beginner on Mac OS X.
- **FreeBSD**: Supportted by community. We didn't test the library on this OS.
## Usages
Link with libopenblas.a or -lopenblas for shared library.
### Set the number of threads with environment variables.
Examples:
export OPENBLAS_NUM_THREADS=4
or
export GOTO_NUM_THREADS=4
or
export OMP_NUM_THREADS=4
The priorities are OPENBLAS_NUM_THREADS > GOTO_NUM_THREADS > OMP_NUM_THREADS.
If you compile this lib with USE_OPENMP=1, you should set OMP_NUM_THREADS environment variable. OpenBLAS ignores OPENBLAS_NUM_THREADS and GOTO_NUM_THREADS with USE_OPENMP=1.
### Set the number of threads on runtime.
We provided the below functions to controll the number of threads on runtime.
void goto_set_num_threads(int num_threads);
void openblas_set_num_threads(int num_threads);
If you compile this lib with USE_OPENMP=1, you should use the above functions, too.
## Report Bugs
Please add a issue in https://github.com/xianyi/OpenBLAS/issues
## Contact
OpenBLAS users mailing list: http://list.rdcps.ac.cn/mailman/listinfo/openblas
## ChangeLog
Please see Changelog.txt to obtain the differences between GotoBLAS2 1.13 BSD version.
## Troubleshooting
* Please read [Faq](https://github.com/xianyi/OpenBLAS/wiki/Faq) at first.
* Please use gcc version 4.6 and above to compile Sandy Bridge AVX kernels on Linux/MingW/BSD.
* Please use Clang version 3.1 and above to compile the library on Sandy Bridge microarchitecture. The Clang 3.0 will generate the wrong AVX binary code.
* The number of CPUs/Cores should less than or equal to 256.
* On Linux, OpenBLAS sets the processor affinity by default. This may cause [the conflict with R parallel](https://stat.ethz.ch/pipermail/r-sig-hpc/2012-April/001348.html). You can build the library with NO_AFFINITY=1.
* On Loongson 3A. make test would be failed because of pthread_create error. The error code is EAGAIN. However, it will be OK when you run the same testcase on shell.
## Specification of Git Branches
We used the git branching model in this article (http://nvie.com/posts/a-successful-git-branching-model/).
Now, there are 4 branches in github.com.
* The master branch. This a main branch to reflect a production-ready state.
* The develop branch. This a main branch to reflect a state with the latest delivered development changes for the next release.
* The loongson3a branch. This is a feature branch. We develop Loongson3A codes on this branch. We will merge this feature to develop branch in future.
* The gh-pages branch. This is for web pages