table of contents
CLCREATECONTEXT(3clc) | OpenCL Manual | CLCREATECONTEXT(3clc) |
NAME¶
clCreateContext - Creates an OpenCL context.¶
cl_context
clCreateContext(const cl_context_properties *properties,
cl_uint num_devices,
const cl_device_id *devices,
(void CL_CALLBACK *pfn_notify) ( .sp .nf const char *errinfo, const void *private_info, size_t cb, void *user_data .fi ),
void *user_data,
cl_int *errcode_ret);
DESCRIPTION¶
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.PARAMETERS¶
propertiesSpecifies 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_dx9_media_sharing(3clc) is enabled, then
properties specifies a list of context property names and their
corresponding values. Each property is followed immediately by the
corresponding desired value. The list is terminated with zero. If a property
is not specified in properties, then its default value (listed in the
table below) 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.
If the extension cl_khr_d3d10_sharing(3clc) is enabled, then
properties specifies a list of context property names and their
corresponding values. Each property is followed immediately by the
corresponding desired value. The list is terminated with zero. 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(3clc) 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..
num_devices
cl_context_properties enum | Property value | Description |
CL_CONTEXT_PLATFORM | cl_platform_id | Specifies the platform to use. |
CL_CONTEXT_INTEROP_USER_SYNC | cl_bool | Specifies whether the user is responsible for synchronization between OpenCL and other APIs. Please refer to the specific sections in the OpenCL 1.2 extension specification that describe sharing with other APIs for restrictions on using this flag. If CL_CONTEXT_INTEROP_USER_ SYNC is not specified, a default of CL_FALSE is assumed. |
CL_CONTEXT_D3D10_DEVICE_KHR | ID3D10Device* | If the cl_khr_d3d10_sharing(3clc) extension is enabled, specifies the ID3D10Device* to use for Direct3D 10 interoperability. The default value is NULL. |
CL_GL_CONTEXT_KHR | 0, OpenGL context handle | OpenGL context to associated the OpenCL context with (available if the cl_khr_gl_sharing(3clc) extension is enabled) |
CL_EGL_DISPLAY_KHR | EGL_NO_DISPLAY, EGLDisplay handle | EGLDisplay an OpenGL context was created with respect to (available if the cl_khr_gl_sharing(3clc) extension is enabled) |
CL_GLX_DISPLAY_KHR | None, X handle | X Display an OpenGL context was created with respect to (available if the cl_khr_gl_sharing(3clc) extension is enabled) |
CL_CGL_SHAREGROUP_KHR | 0, CGL share group handle | CGL share group to associate the OpenCL context with (available if the cl_khr_gl_sharing(3clc) extension is enabled) |
CL_WGL_HDC_KHR | 0, HDC handle | HDC an OpenGL context was created with respect to (available if the cl_khr_gl_sharing(3clc) extension is enabled) |
CL_CONTEXT_ADAPTER_D3D9_KHR | IDirect3DDevice9 * | Specifies an IDirect3DDevice9 to use for D3D9 interop (if the cl_khr_dx9_media_sharing(3clc) extension is supported). |
CL_CONTEXT_ADAPTER_D3D9EX_KHR | IDirect3DDeviceEx* | Specifies an IDirect3DDevice9Ex to use for D3D9 interop (if the cl_khr_dx9_media_sharing(3clc) extension is supported). |
CL_CONTEXT_ADAPTER_DXVA_KHR | IDXVAHD_Device * | Specifies an IDXVAHD_Device to use for DXVA interop (if the cl_khr_dx9_media_sharing(3clc) extension is supported). |
CL_CONTEXT_D3D11_DEVICE_KHR | ID3D11Device * | Specifies the ID3D11Device * to use for Direct3D 11 interoperability. The default value is NULL. |
The number of devices specified in the devices
argument.
devices
A pointer to a list of unique devices returned by
clGetDeviceIDs(3clc) or sub-devices created by
clCreateSubDevices(3clc) for a platform.
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 during context creation as well as errors that
occur at runtime 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.
NOTES¶
clCreateContext and clCreateContextFromType(3clc) 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.ERRORS¶
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:•CL_INVALID_PLATFORM if 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(3clc) is enabled, then this error is replaced with
CL_INVALID_GL_SHAREGROUP_REFERENCE_KHR; see below.)
•CL_INVALID_PROPERTY if context property name in
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(3clc) is enabled, then CL_INVALID_PROPERTY is
returned if an attribute name other than those listed in the table for
properties above or if CL_CONTEXT_INTEROP_USER_SYNC is specified
in properties.
•CL_INVALID_PROPERTY if an attribute name other
than those specified in table 4.5 or if CL_CONTEXT_INTEROP_USER_SYNC is
specified in properties.
•CL_INVALID_VALUE if devices is NULL; if
num_devices is equal to zero; or if pfn_notify is NULL but
user_data is not NULL.
•CL_INVALID_DEVICE if devices contains an
invalid device.
•CL_INVALID_OPERATION if Direct3D 10
interoperability is specified by setting CL_INVALID_D3D10_DEVICE_KHR to
a non-NULL value, and interoperability with another graphics API is also
specified (if the cl_khr_d3d10_sharing(3clc) extension is
enabled).
•CL_DEVICE_NOT_AVAILABLE if a device in
devices is currently not available even though the device was returned
by clGetDeviceIDs(3clc).
•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.
•CL_INVALID_D3D10_DEVICE_KHR if the Direct3D 10
device specified for interoperability is not compatible with the devices
against which the context is to be created (if the
cl_khr_d3d10_sharing(3clc) extension is enabled).
•CL_INVALID_D3D10_DEVICE_KHR if the value of the
property CL_CONTEXT_D3D10_DEVICE_KHR is non-NULL and does not specify a
valid Direct3D 10 device with which the cl_device_ids against which
this context is to be created may interoperate (if the
cl_khr_d3d10_sharing(3clc) extension is enabled).
•CL_INVALID_GL_SHAREGROUP_REFERENCE_KHR when an
invalid OpenGL context or share group object handle is specified in
properties (only if the cl_khr_gl_sharing(3clc) extension is
enabled).
•CL_INVALID_GL_SHAREGROUP_REFERENCE_KHR if no
OpenGL or OpenGL ES context or share group is specified in the attribute list
given to clCreateContext(3clc) and any of the commands in section 9.7
are called. (if the cl_khr_gl_sharing(3clc) extension is enabled)
•CL_INVALID_GL_SHAREGROUP_REFERENCE_KHR if the
cl_khr_gl_sharing(3clc) extension is enabled and if a context was
specified by any of the following means:
• A context specified for an EGL-based OpenGL ES
or OpenGL implementation by setting the attributes CL_GL_CONTEXT_KHR
and CL_EGL_DISPLAY_KHR.
• A context was specified for a GLX-based OpenGL
implementation by setting the attributes CL_GL_CONTEXT_KHR and
CL_GLX_DISPLAY_KHR.
• A context was specified for a WGL-based OpenGL
implementation by setting the attributes CL_GL_CONTEXT_KHR and
CL_WGL_HDC_KHR.
and any of the following conditions hold:
• The specified display and context attributes do
not identify a valid OpenGL or OpenGL ES context.
• The specified context does not support buffer
and renderbuffer objects.
• The specified context is not compatible with the
OpenCL context being created (for example, it exists in a physically distinct
address space, such as another hardware device, or does not support sharing
data with OpenCL due to implementation restrictions).
•CL_INVALID_GL_SHAREGROUP_REFERENCE_KHR if a share
group was specified for a CGL-based OpenGL implementation by setting the
attribute CL_CGL_SHAREGROUP_KHR, and the specified share group does not
identify a valid CGL share group object (if the cl_khr_gl_sharing(3clc)
extension is enabled).
•CL_INVALID_OPERATION if a context was specified
as described above and any of the following conditions hold:
• A context or share group object was specified
for one of CGL, EGL, GLX, or WGL and the OpenGL implementation does not
support that window-system binding API.
• More than one of the attributes
CL_CGL_SHAREGROUP_KHR, CL_EGL_DISPLAY_KHR,
CL_GLX_DISPLAY_KHR, and CL_WGL_HDC_KHR is set to a non-default
value.
• Both of the attributes
CL_CGL_SHAREGROUP_KHR and CL_GL_CONTEXT_KHR are set to
non-default values.
• Any of the devices specified in the devices
argument cannot support OpenCL objects which share the data store of an OpenGL
object, as described in section 9.7.
•CL_INVALID_DX9_MEDIA_ADAPTER_KHR if the media
adapter specified for interoperability is not compatible with the devices
against which the context is to be created (only if the
cl_khr_dx9_media_sharing(3clc) extension is supported).
•CL_INVALID_ADAPTER_KHR if any of the values of
the properties CL_CONTEXT_ADAPTER_D3D9_KHR,
CL_CONTEXT_ADAPTER_D3D9EX_KHR or CL_CONTEXT_ADAPTER_DXVA_KHR is
non-NULL and does not specify a valid media adapter with which the
cl_device_ids against which this context is to be created may interoperate
(only if the cl_khr_dx9_media_sharing(3clc) extension is
supported).
•CL_INVALID_OPERATION if interoperability is
specified by setting CL_CONTEXT_ADAPTER_D3D9_KHR,
CL_CONTEXT_ADAPTER_D3D9EX_KHR or CL_CONTEXT_ADAPTER_DXVA_KHR to
a non-NULL value, and interoperability with another graphics API is also
specified (only if the cl_khr_dx9_media_sharing(3clc) extension is
supported).
•CL_INVALID_OPERATION if Direct3D 11
interoperability is specified by setting CL_INVALID_D3D11_DEVICE_KHR to
a non-NULL value, and interoperability with another graphics API is also
specified (only if the cl_khr_d3d11_sharing(3clc) extension is
supported).
•CL_INVALID_D3D11_DEVICE_KHR if the value of the
property CL_CONTEXT_D3D11_DEVICE_KHR is non-NULL and does not specify a
valid Direct3D 11 device with which the cl_device_ids against which
this context is to be created may interoperate (only if the
cl_khr_d3d11_sharing(3clc) extension is supported).
•CL_INVALID_D3D11_DEVICE_KHR if the Direct3D 11
device specified for interoperability is not compatible with the devices
against which the context is to be created (only if the
cl_khr_d3d11_sharing(3clc) extension is supported).
SPECIFICATION¶
OpenCL Specification[1]SEE ALSO¶
clGetDeviceIDs(3clc), clCreateContextFromType(3clc), clRetainContext(3clc), clReleaseContext(3clc), clGetContextInfo(3clc), classDiagram(3clc)AUTHORS¶
The Khronos GroupCOPYRIGHT¶
Copyright © 2007-2011 The Khronos Group Inc.NOTES¶
- 1.
- OpenCL Specification
page 54, section 4.4 - Contexts
06/18/2014 | The Khronos Group |