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clCreateBuffer.adoc

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clCreateBuffer

Creates a buffer object.

cl_mem clCreateBuffer(cl_context context,
                      cl_mem_flags flags,
                      size_t size,
                      void *host_ptr,
                      cl_int *errcode_ret)

Parameters

context

A valid OpenCL context used to create the buffer object.

flags

A bit-field that is used to specify allocation and usage information such as the memory arena that should be used to allocate the buffer object and how it will be used. The following table describes the possible values for flags. If value specified for flags is 0, the default is used which is CL_MEM_READ_WRITE.

size

The size in bytes of the buffer memory object to be allocated.

host_ptr

A pointer to the buffer data that may already be allocated by the application. The size of the buffer that host_ptr points to must be ≥ size bytes.

errcode_ret

Returns an appropriate error code. If errcode_ret is NULL, no error code is returned.

Notes

The user is responsible for ensuring that data passed into and out of OpenCL images are natively aligned relative to the start of the buffer as per kernel language or IL requirements. OpenCL buffers created with CL_MEM_USE_HOST_PTR need to provide an appropriately aligned host memory pointer that is aligned to the data types used to access these buffers in a kernel(s).

If clCreateBuffer is called with a pointer returned by clSVMAlloc as its host_ptr argument, and CL_MEM_USE_HOST_PTR is set in its flags argument, clCreateBuffer will succeed and return a valid non-zero buffer object as long as the size argument to clCreateBuffer is no larger than the size argument passed in the original clSVMAlloc call. The new buffer object returned has the shared memory as the underlying storage. Locations in the buffer’s underlying shared memory can be operated on using atomic operations to the device’s level of support as defined in the memory model.

Errors

Returns a valid non-zero buffer object and errcode_ret is set to CL_SUCCESS if the buffer object is created successfully. Otherwise, it returns a NULL value with one of the following error values returned in errcode_ret:

  • CL_INVALID_CONTEXT if context is not a valid context.

  • CL_INVALID_VALUE if values specified in flags are not valid as defined in the table above.

  • CL_INVALID_BUFFER_SIZE if size is 0.

    Implementations may return CL_INVALID_BUFFER_SIZE if size is greater than the CL_DEVICE_MAX_MEM_ALLOC_SIZE value specified in the table of allowed values for param_name for clGetDeviceInfo for all devices in context.

  • CL_INVALID_HOST_PTR if host_ptr is NULL and CL_MEM_USE_HOST_PTR or CL_MEM_COPY_HOST_PTR are set in flags or if host_ptr is not NULL but CL_MEM_COPY_HOST_PTR or CL_MEM_USE_HOST_PTR are not set in flags.

  • CL_MEM_OBJECT_ALLOCATION_FAILURE if there is a failure to allocate memory for buffer object.

  • CL_OUT_OF_RESOURCES if there is a failure to allocate resources required by the OpenCL implementation on the device.

  • CL_OUT_OF_HOST_MEMORY if there is a failure to allocate resources required by the OpenCL implementation on the host.