In CUDA, launching a kernel means specifying its arguments, marshaled via an array of pointers:
CUresult cuLaunchKernel ( CUfunction f, /* launch config stuff */, void** kernelParams, /* snip */ ); CUresult cuLaunchKernelEx ( const CUlaunchConfig* config, CUfunction f, void** kernelParams, /* snip */ ) ; and after the launch - you've still got that array of pointers to argument values, and you can do whatever you want with it: Launch again, alter and then launch etc.
In OpenCL, though, kernel arguments are set one-by-one, and opaquely:
cl_int clSetKernelArg( cl_kernel kernel, cl_uint arg_index, size_t arg_size, const void* arg_value); So, you set, set, set a few times, then launch the kernel (using clEnqueueNDRangeKernel()). The interesting aspect of this is that cl_kernel does not represent just a piece of device-side-executable code, but rather additional state, including the arguments you've set.
My question is: What assumptions can I make about this state, and the arguments I've set, after a launch of a kernel? Can I assume everything is as it was just before the launch, and I can alter just some arguments, keeping the rest, for another launch of the same kernel? Or - are they invalidated/lost somehow, and have to be fully set again? ... and maybe this is implementation-dependent?
