Do you know of any samples where the device fission extension is used?
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Currently, no. You can expect a sample in one of the upcoming releases.
- Can I have both 8 command queues for the cores of the CPU as well as a command queue for the parent device (the entire CPU)? So I could use the individual cores for the raycasting, but then use the entire CPU for post-processing |
Yes, you can. Attaching example OpenCL code using the extension.
On machine that has a CPU device with 8 cores (real or hyper-threaded), the given code will give you 8 sub-devices.
- Can I build the program with only one build call using all subdevices and the parent device as parameter? |
The intended behavior is that a single program can be built against the parent device and kernel objects constructed from the resulting programs can be run against any of the sub-device queues.
- If I use only one program can I use only one instance of the kernels as well? And they could all work using the same kernel with different arguments? at the same time? |
You can share the same kernel object in the case that you set the arguments and then call enqueueNDRange and then set kernel args and call the next enqueueNDRange, all from within the same thread. However, if you intend to call the same kernel from different threads, then the kernel object is not thread safe and you may see races, along with possible data corruption. The threading issue can easily be worked around by simply creating a kernel object for each queue that will be dispatched from a different thread.
- can you somehow use the device fission extension with the OpenCL 1.1 C++ bindings and the current StreamSDK? If I define USE_CL_DEVICE_FISSION it won't compile because the cl_ext.h is still in revision 10424 instead of 11702 |
You can expect OpenCL 1.1 support in the upcoming release.
cl:: CommandQueue parentQueue; std::vector<cl:: CommandQueue> subQueues; std::vector<cl::Platform> platforms; std::vector<cl::Device> subDevices; cl::Platform::get(&platforms); if (platforms.size() == 0) { std::cout << "Platform size 0\n"; return -1; } cl_context_properties properties[] = { CL_CONTEXT_PLATFORM, (cl_context_properties)(platforms[0])(), 0}; // CPU device only supports fission, currently context = cl::Context(CL_DEVICE_TYPE_CPU, properties); std::vector<cl::Device> devices = context.getInfo<CL_CONTEXT_DEVICES>(); // Check that device fission is supported – just use first device if (devices[0].getInfo<CL_DEVICE_EXTENSIONS>().find("cl_ext_device_fission") == std::string::npos) { std::cout << "Required that device support cl_ext_device_extension" << std::endl; return -1; } cl_device_partition_property_ext subDeviceProperties[] = { CL_DEVICE_PARTITION_EQUALLY_EXT, 1, CL_PROPERTIES_LIST_END_EXT, 0}; devices[0].createSubDevices(subDeviceProperties, &subDevices); if (subDevices.size() <= 0) { std::cout << "Failed to allocate subdevices" << std::endl; return -1; } std::cout << "Number of sub-devices " << subDevices.size() << std::endl; // create command queue for parent device parentQueue = cl::CreateQueue(context,devices[0]); // create command queues for the sub-devices for (std::vector<cl::Device>::iterator i = subDevices.begin(); i != subDevices.end(); i++) { subQueues.push_back(cl::CommandQueue(context, *i)); }
