accessing file system using cpu device in opencl

问题:

I am a newbie to opencl. I have a doubt about opencl functioning when kernel is running on a cpu device.Suppose we have a kernel running on a cpu device, can it read from a file on the disk. If yes,then how ? If no , then why not ? Can you please suggest a source for detailed information ?? thanks in advance.

回答1:

You can't. OpenCL is trying to unite access to computing power and file system is depending on OS. If you want this feature, there are threads (C++11 thread, pthread,...) or OpenMP should be able to handle this, because it's CPU-only thing.

回答2:

It can't. Simply because not every OpenCL device has a file system, or a disk respectively.

回答3:

It doesn't make sense to allow device kernels to access the filesystem, because most of the semantics of filesystem access are essentially incompatible with the massively parallel nature of device kernels.

There are two ways to work around this, considering you're only asking about CPU.

1. if you intend to use OpenCL as a way to do multithreading on CPU, consider using what OpenCL calls “native kernels”, which are essentially just plain C functions, called within an OpenCL context;

2. a more general approach that might work on GPU too would be to mmap the files you want to operate on, and pass the resulting pointers to clCreateBuffer with CL_USE_HOST_PTR flags.