path: root/docs/Beignet.mdwn

Beignet
=======

Beignet is an open source implementation of the OpenCL specification - a generic
compute oriented API. This code base contains the code to run OpenCL programs on
Intel GPUs which basically defines and implements the OpenCL host functions
required to initialize the device, create the command queues, the kernels and
the programs and run them on the GPU. The code base also contains the compiler
part of the stack which is included in `backend/`. For more specific information
about the compiler, please refer to `backend/README.md`

News
----
[[Beignet project news|Beignet/NEWS]]

Prerequisite
------------

The project depends on the following external libaries:

- libdrm libraries (libdrm and libdrm\_intel)
- Various LLVM components
- If run with X server, beignet needs XLib, Xfixes and Xext installed. Otherwise, no X11 dependency.

And if you want to work with the standard ICD libOpenCL.so, then you need
two more packages (the following package name is for Ubuntu):

- ocl-icd-dev
- ocl-icd-libopencl1

If you don't want to enable ICD, or your system doesn't have ICD OpenCL support,
you can still link to the beignet OpenCL library. You can find the beignet/libcl.so
in your system's library installation directories.

Note that the compiler depends on LLVM (Low-Level Virtual Machine project).
Right now, the code has been compiled with LLVM 3.3/3.4. It will not compile
with anything older.

[http://llvm.org/releases/](http://llvm.org/releases/)


**The recommended LLVM/CLANG version is 3.5 and/or 3.6**

Based on our test result, LLVM 3.5 has best pass rate on all the test suites. LLVM 3.6
has slightly less pass rate(caused by one front end bug at clang 3.6) than 3.5 but has
better performance about 3% to 8% for different cases and different targets.

For LLVM 3.3 and 3.4, Beignet still support them, but it may be limited to support the
build and major functions.

How to build and install
------------------------

The project uses CMake with three profiles:

1. Debug (-g)
2. RelWithDebInfo (-g with optimizations)
3. Release (only optimizations)

Basically, from the root directory of the project

`> mkdir build`

`> cd build`

`> cmake ../ # to configure`

Please be noted that the code was compiled on GCC 4.6, GCC 4.7 and GCC 4.8 and CLANG 3.5 and
ICC 14.0.3. Since the code uses really recent C++11 features, you may expect problems with
older compilers. The default compiler should be GCC, and if you want to choose compiler manually,
you need to configure it as below:
`> cmake -DCOMPILER=[GCC|CLANG|ICC] ../`

CMake will check the dependencies and will complain if it does not find them.

`> make`

The cmake will build the backend firstly. Please refer to:
[[OpenCL Gen Backend|Beignet/Backend]] to get more dependencies.

Once built, the run-time produces a shared object libcl.so which basically
directly implements the OpenCL API. A set of tests are also produced. They may
be found in `utests/`.

Simply invoke:
`> make install`

It installs the following six files to the beignet/ directory relatively to
your library installation directory.
- libcl.so
- libgbeinterp.so
- libgbe.so
- ocl\_stdlib.h, ocl\_stdlib.h.pch
- beignet.bc

It installs the OCL icd vendor files to /etc/OpenCL/vendors, if the system support ICD.
- intel-beignet.icd

How to run
----------

After build and install of beignet, you may need to check whether it works on your
platform. Beignet also produces various tests to ensure the compiler and the run-time
consistency. This small test framework uses a simple c++ registration system to
register all the unit tests.

You need to call setenv.sh in the utests/ directory to set some environment variables
firstly as below:

`> . setenv.sh`

Then in `utests/`:

`> ./utest_run`

will run all the unit tests one after the others

`> ./utest_run some_unit_test0 some_unit_test1`

will only run `some_unit_test0` and `some_unit_test1` tests

On all supported target platform, the pass rate should be 100%. If it is not, you may
need to refer the "Known Issues" section. Please be noted, the `. setenv.sh` is only
required to run unit test cases. For all other OpenCL applications, don't execute that
command.

Normally, beignet needs to run under X server environment as normal user. If there isn't X server,
beignet provides two alternative to run:
* Run as root without X.
* Enable the drm render nodes by passing drm.rnodes=1 to the kernel boot args, then you can run beignet with non-root and without X.

Supported Targets
-----------------

 * 3rd Generation Intel Core Processors
 * Intel “Bay Trail” platforms with Intel HD Graphics
 * 4th Generation Intel Core Processors, need kernel patch currently, see the "Known Issues" section.
 * 5th Generation Intel Core Processors "Broadwell".

Known Issues
------------

* GPU hang issues.
  To check whether GPU hang, you could execute dmesg and check whether it has the following message:
  `[17909.175965] [drm:i915_hangcheck_hung] *ERROR* Hangcheck timer elapsed...`
  If it does, there was a GPU hang. Usually, this means something wrong in the kernel, as it indicates
  the OCL kernel hasn't finished for about 6 seconds or even more. If you think the OCL kernel does need
  to run that long and have confidence with the kernel, you could disable the linux kernel driver's
  hang check feature to fix this hang issue. Just invoke the following command on Ubuntu system:

  `# echo -n 0 > /sys/module/i915/parameters/enable_hangcheck`

  But this command is a little bit dangerous, as if your kernel really hang, then the gpu will lock up
  forever until a reboot.

* Almost all unit tests fail on Linux kernel 3.15/3.16.
  There is a known issue in some versions of linux kernel which enable register whitelist feature
  but miss some necessary registers which are required for beignet. The problematic version are
  around 3.15 and 3.16 which have commit f0a346b... but haven't commit c9224f... If it is the case,
  you can apply c9224f... manually and rebuild the kernel or just disable the parse command by
  invoke the following command (use Ubuntu as an example):
  `# echo 0 > /sys/module/i915/parameters/enable_cmd_parser`

* Some unit test cases, maybe 20 to 30, fail on 4th Generation (HSW) platform.
  _The 4th Generation Intel Core Processors's support requires some Linux kernel
  modification_. You need to apply the patch at:  
  [https://01.org/zh/beignet/downloads/linux-kernel-patch-hsw-support](https://01.org/zh/beignet/downloads/linux-kernel-patch-hsw-support)

* Precision issue.
  Currently Gen does not provide native support of high precision math functions
  required by OpenCL. We provide a software version to achieve high precision,
  which you can turn on through `export OCL_STRICT_CONFORMANCE=1`.
  But be careful, this would make your CL kernel run a little longer.

* cl\_khr\_gl\_sharing.
  This extension highly depends on mesa support. It seems that mesa would not provide
  such type of extensions, we may have to hack with mesa source code to support this
  extension. This feature used to work with a previous mesa git version. But now, it's
  simply broken.

TODO
----

In terms of the OpenCL 1.2 spec, beignet is quite complete now. We can pass almost
all the piglit OpenCL test cases now. And the pass rate for the OpenCV test suite
is also good which is about 99%. There are still some remains work items listed as below,
most of them are extension support and performance related.

- Performance tuning. There are some major optimizations need to be done,
  Peephole optimization, futher tuning the structurized BB transformation to
  support more pattern such as self loop/while loop. And optimize the slow
  software based sin/cos/... math functions due to the native math instruction
  lack of necessary precision. And all the code is inlined which will increase
  the icache miss rate significantly. And many other things which are specified
  partially in [[here|Beignet/Backend/TODO]].

- Complete cl\_khr\_gl\_sharing support. We lack of some APIs implementation such
  as clCreateFromGLBuffer,clCreateFromGLRenderbuffer,clGetGLObjectInfo... Currently,
  the working APIs are clCreateFromGLTexture,clCreateFromGLTexture2D. We may need to
  find a graceful way to co-work with mesa.

- Check that NDRangeKernels can be pushed into _different_ queues from several
  threads.

- No state tracking at all. One batch buffer is created at each "draw call"
  (i.e. for each NDRangeKernels). This is really inefficient since some
  expensive pipe controls are issued for each batch buffer.

More generally, everything in the run-time that triggers the "FATAL" macro means
that something that must be supported is not implemented properly (either it
does not comply with the standard or it is just missing)

Project repository
------------------
Right now, we host our project on fdo at:
[http://cgit.freedesktop.org/beignet/](http://cgit.freedesktop.org/beignet/).  
And the intel 01.org:
[https://01.org/beignet](https://01.org/beignet)

The team
--------
Beignet project was created by Ben Segovia. Since 2013, Now Intel China OTC graphics
team continue to work on this project. The official contact for this project is:  
Zou Nanhai (<nanhai.zou@intel.com>).

How to contribute
-----------------
You are always welcome to contribute to this project, just need to subscribe
to the beignet mail list and send patches to it for review.
The official mail list is as below:
[http://lists.freedesktop.org/mailman/listinfo/beignet](http://lists.freedesktop.org/mailman/listinfo/beignet)  
The official bugzilla is at:
[https://bugs.freedesktop.org/enter_bug.cgi?product=Beignet](https://bugs.freedesktop.org/enter_bug.cgi?product=Beignet)  
You are welcome to submit beignet bug. Please be noted, please specify the exact platform
information, such as BYT/IVB/HSW/BDW, and GT1/GT2/GT3. You can easily get this information
by running the beignet's unit test.

Documents for OpenCL application developers
-------------------------------------------
- [[Cross compile|Beignet/howto/cross-compiler-howto]]
- [[Kernel Optimization Guide|Beignet/optimization-guide]]
- [[Libva Buffer Sharing|Beignet/howto/libva-buffer-sharing-howto]]

The wiki URL is as below:
[http://www.freedesktop.org/wiki/Software/Beignet/](http://www.freedesktop.org/wiki/Software/Beignet/)