OpenBLAS/README

OpenBLAS Readme

1.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)

2.Intallation
Download from project homepage. http://xianyi.github.com/OpenBLAS/
Or,
check out codes from git://github.com/xianyi/OpenBLAS.git
1)Normal compile
  (a) type "make" to detect the CPU automatically.
  or
  (b) type "make TARGET=xxx" to set target CPU, e.g. "make TARGET=NEHALEM". The full target list is in file TargetList.txt.

2)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

3)Debug version
make DEBUG=1

4)Intall to the directory (Optional)
e.g.
make install PREFIX=your_installation_directory
The default directory is /opt/OpenBLAS

3.Support CPU & OS
Please read GotoBLAS_01Readme.txt

Additional support CPU:
x86_64:
	Intel Xeon 56xx (Westmere) //Used GotoBLAS2 Nehalem codes.
MIPS64:
	ICT Loongson 3A //The initial version used GotoBLAS2 MIPS64 kernels. Thus, the performance is not good.

4.Usages
Link with libopenblas.a or -lopenblas for shared library.

4.1 Set the number of threads with environment variables. for example,
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.

4.2 Set the number of threads with calling functions. for example,
void goto_set_num_threads(int num_threads);
or
void openblas_set_num_threads(int num_threads);

If you compile this lib with USE_OPENMP=1, you should use the above functions, too.

5.Report Bugs
Please add a issue in https://github.com/xianyi/OpenBLAS/issues

6.To-Do List:
Optimization on ICT Loongson 3A CPU

7.Contact
OpenBLAS users mailing list: http://list.rdcps.ac.cn/mailman/listinfo/openblas

8.ChangeLog
Please see Changelog.txt to obtain the differences between GotoBLAS2 1.13 BSD version.

9.Known Issues
* The number of CPUs/Cores should less than or equal to 8*sizeof(unsigned long). On 64 bits, the limit 
  is 64. On 32 bits, it is 32.
* 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. I don't think this is a bug in OpenBLAS. 

10. 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