cl_context clCreateContext(
| const cl_context_properties *properties, |
cl_uint num_devices, | |
const cl_device_id *devices, | |
(voidCL_CALLBACK *pfn_notify)
( ) , |
|
void *user_data, | |
cl_int *errcode_ret) |
An OpenCL context is created with one or more devices. Contexts are used by the OpenCL runtime for managing objects such as command-queues, memory, program and kernel objects and for executing kernels on one or more devices specified in the context.
Specifies a list of context property names and their corresponding values. Each property name is
immediately followed by the corresponding desired value. The list is terminated with 0.
properties
can be NULL in which case the platform that is selected is
implementation-defined. The list of supported properties
is described in the table below.
If the extension cl_khr_d3d10_sharing
is enabled, then if a property is not specified in properties
, then its default value is used
(it is said to be specified implicitly). If properties
is NULL or empty (points to a list
whose first value is zero), all attributes take on their default value.
If the extension cl_khr_gl_sharing
is enabled, then properties
points to an attribute list, which is a array of ordered <attribute name, value> pairs terminated with zero. If an attribute is not specified in properties
, then its default value is used (it is said to be specified implicitly). If properties
is NULL or empty (points to a list whose first value is zero), all attributes take on their default values..
cl_context_properties enum | Property value | Description |
---|---|---|
CL_CONTEXT_PLATFORM
|
cl_platform_id | Specifies the platform to use. |
CL_CONTEXT_D3D10_DEVICE_KHR
|
ID3D10Device* | If the cl_khr_d3d10_sharing extension is enabled, specifies the ID3D10Device* to use for Direct3D 10 interoperability. The default value is NULL. |
|
Available if the cl_khr_gl_sharing extension is enabled. |
num_devices
The number of devices specified in the devices
argument.
devices
A pointer to a list of unique devices returned by clGetDeviceIDs
for a platform. Duplicate devices specified in devices
are ignored.
pfn_notify
A callback function that can be registered by the application. This callback function will be used by the OpenCL implementation to report information on errors that occur in this context. This callback function may be called asynchronously by the OpenCL implementation.
It is the application's responsibility to ensure that the callback function is thread-safe. If pfn_notify
is NULL, no callback function is registered. The parameters to this callback function are:
errinfo
is a pointer to an error string.
private_info
and cb
represent a pointer to binary data that is returned by the OpenCL implementation that can be used to log additional information helpful in debugging the error.
user_data
is a pointer to user supplied data.
NOTE: There are a number of cases where error notifications need to be delivered due to an error that occurs outside a context. Such notifications may not be delivered through the pfn_notify
callback. Where these notifications go is implementation-defined.
user_data
Passed as the user_data
argument when pfn_notify
is called. user_data
can be NULL.
errcode_ret
Returns an appropriate error code. If errcode_ret
is NULL, no error code is returned.
clCreateContext
and clCreateContextFromType perform an implicit retain. This is very helpful for 3rd party libraries, which typically get a context passed to them by the application.
However, it is possible that the application may delete the context without informing the library.
Allowing functions to attach to (i.e. retain) and release a context solves the problem of a context
being used by a library no longer being valid.
clCreateContext
returns a valid non-zero context and errcode_ret
is set to CL_SUCCESS if the context is created successfully. Otherwise, it returns NULL value with the following error
values returned in errcode_ret
:
properties
is NULL and no platform could be selected or if platform value specified in properties
is not a valid platform. (If the extension cl_khr_gl_sharing is enabled, then see error "CL_INVALID_GL_SHAREGROUP_REFERENCE_KHR" below.)
properties
is not a supported
property name, if the value specified for a supported property name is not valid, or if the
same property name is specified more than once. However if the extension cl_khr_gl_sharing is enabled, then CL_INVALID_PROPERTY is returned if an attribute name other than those listed in the table for properties
above is specified in properties
.
devices
is NULL; if num_devices
is equal to zero; or
if pfn_notify
is NULL but user_data
is not NULL.
devices
contains an invalid device.
devices
is currently not available
even though the device was returned by clGetDeviceIDs.
cl_device_ids
against which this context
is to be created may interoperate (if the
cl_khr_d3d10_sharing extension is enabled).
properties
(only if the
cl_khr_gl_sharing extension is enabled).
clGetDeviceIDs, clCreateContextFromType, clRetainContext, clReleaseContext, clGetContextInfo, Cardinality Diagram