Provided by: opencl-1.2-man-doc_1.0~svn22836-1.1_all 
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
properties
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_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..
┌──────────────────────────────┬──────────────────────────┬────────────────────────────────┐
│cl_context_properties │ Property value │ Description │
│enum │ │ │
├──────────────────────────────┼──────────────────────────┼────────────────────────────────┤
│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 an OpenGL │
│ │ EGLDisplay handle │ 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 │ CGL share group to │
│ │ handle │ 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. │
└──────────────────────────────┴──────────────────────────┴────────────────────────────────┘
num_devices
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 Group
COPYRIGHT
Copyright © 2007-2011 The Khronos Group Inc.
Permission is hereby granted, free of charge, to any person obtaining a copy of this
software and/or associated documentation files (the "Materials"), to deal in the Materials
without restriction, including without limitation the rights to use, copy, modify, merge,
publish, distribute, sublicense, and/or sell copies of the Materials, and to permit
persons to whom the Materials are furnished to do so, subject to the condition that this
copyright notice and permission notice shall be included in all copies or substantial
portions of the Materials.
NOTES
1. OpenCL Specification
page 54, section 4.4 - Contexts