opencl memory creation

How to create memory on OpenCL device

• CL_MEM_USE_HOST_PTR

  • Use host memory directly, which could be accessed by device directly.
  • Host and device could access the memory directly, without cl mapping, clEnqueueMapBuffer()
  • Both host and device use the unique host memory.

• CL_MEM_ALLOC_HOST_PTR

  • Allocate memory on device side, like vram
  • Host could access the memory by clEnqueueMapBuffer()
  • If set it only, host_ptr must be NULL.
  • If set it with CL_MEM_COPY_HOST_PTR, host_ptr must be non-NULL.
  • Invalid to use CL_MEM_USE_HOST_PTR and CL_MEM_ALLOC_HOST_PTR.

• CL_MEM_COPY_HOST_PTR

  • Copy memory from host to device, host_ptr must be non-NULL.
  • The host_ptr is different from copied memory on device

• reference

  • OpenCL1.2: Increase perofrmance on Intel Processor Graphics