clGetDeviceIDs
clGetDeviceIDs
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clGetDeviceIDs Obtain the list of devices available on a platform.

##

cl_int `clGetDeviceIDs` cl_platform_id platform cl_device_type device_type cl_uint num_entries cl_device_id *devices cl_uint *num_devices

## Parameters

`platform`

  Refers to the platform ID returned by clGetPlatformIDs or can be NULL. If `platform` is NULL, the behavior is implementation-defined.

`device_type`

  A bitfield that identifies the type of OpenCL device. The `device_type` can be used to query specific OpenCL devices or all OpenCL devices available. The valid values for `device_type` are specified in the following table.

  cl_device_type | Description
  --- | ---
  `CL_DEVICE_TYPE_CPU` | An OpenCL device that is the host processor. The host processor runs the OpenCL implementations and is a single or multi-core CPU.
  `CL_DEVICE_TYPE_GPU` | An OpenCL device that is a GPU. By this we mean that the device can also be used to accelerate a 3D API such as OpenGL or DirectX.
  `CL_DEVICE_TYPE_ACCELERATOR` | Dedicated OpenCL accelerators (for example the IBM CELL Blade). These devices communicate with the host processor using a peripheral interconnect such as PCIe.
  `CL_DEVICE_TYPE_CUSTOM` | Dedicated accelerators that do not support programs written in OpenCL C.
  `CL_DEVICE_TYPE_DEFAULT` | The default OpenCL device in the system. The default device cannot be a `CL_DEVICE_TYPE_CUSTOM` device.
  `CL_DEVICE_TYPE_ALL` | All OpenCL devices available in the system except `CL_DEVICE_TYPE_CUSTOM` devices.

`num_entries`

  The number of cl_device_id entries that can be added to `devices`. If `devices` is not NULL, the `num_entries` must be greater than zero.

`devices`

  A list of OpenCL devices found. The cl_device_id values returned in `devices` can be used to identify a specific OpenCL device. If `devices` argument is NULL, this argument is ignored. The number of OpenCL devices returned is the mininum of the value specified by `num_entries` or the number of OpenCL devices whose type matches `device_type`.

`num_devices`

  The number of OpenCL devices available that match `device_type`. If `num_devices` is NULL, this argument is ignored.

## Notes

`clGetDeviceIDs` may return all or a subset of the actual physical devices present in the platform and that match `device_type`.

## Errors

`clGetDeviceIDs` returns CL_SUCCESS if the function is executed successfully. Otherwise it returns one of the following:

- CL_INVALID_PLATFORM if `platform` is not a valid platform.
- CL_INVALID_DEVICE_TYPE if `device_type` is not a valid value.
- CL_INVALID_VALUE if `num_entries` is equal to zero and `devices` is not NULL or if both `num_devices` and `devices` are NULL.
- CL_DEVICE_NOT_FOUND if no OpenCL devices that matched `device_type` were found.
- 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.

## Specification

OpenCL Specification

## Also see

clGetDeviceInfo, clGetPlatformIDs, clCreateContext, Cardinality Diagram

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