Provided by: opencl-1.2-man-doc_1.0~svn33624-5_all 
NAME
clCreateSubDevices - Creates an array of sub-devices that each reference a non-intersecting set of
compute units within in_device.
cl_int clCreateSubDevices(cl_device_id in_device, const cl_device_partition_property *properties,
cl_uint num_devices, cl_device_id *out_devices, cl_uint *num_devices_ret);
PARAMETERS
in_device
The device to be partitioned.
properties
Specifies how in_device is to be partition described by a partition name and its corresponding value.
Each partition name is immediately followed by the corresponding desired value. The list is
terminated with 0. The list of supported partitioning schemes is described in the table below. Only
one of the listed partitioning schemes can be specified in properties.
┌──────────────────────────────────────┬──────────────────────────────────────────────┐
│cl_device_partition_ property enum │ Description │
│(Partition value) │ │
├──────────────────────────────────────┼──────────────────────────────────────────────┤
│CL_DEVICE_PARTITION_EQUALLY (unsigned │ Split the aggregate device into as │
│int) │ many smaller aggregate devices as can │
│ │ be created, each containing n compute │
│ │ units. The value n is passed as the │
│ │ value accompanying this property. If │
│ │ n does not divide evenly into │
│ │ CL_DEVICE_PARTITION_MAX_COMPUTE_UNITS, │
│ │ then the remaining compute units are │
│ │ not used. │
├──────────────────────────────────────┼──────────────────────────────────────────────┤
│CL_DEVICE_PARTITION_BY_COUNTS │ This property is followed by a │
│(unsigned int) │ CL_DEVICE_PARTITION_BY_COUNTS_LIST_END │
│ │ terminated list of compute unit │
│ │ counts. For each nonzero count m in │
│ │ the list, a sub-device is created with │
│ │ m compute units in it. │
│ │ CL_DEVICE_PARTITION_BY_COUNTS_LIST_END │
│ │ is defined to be 0. │
│ │ │
│ │ The number of non-zero count entries │
│ │ in the list may not exceed │
│ │ CL_DEVICE_PARTITION_MAX_SUB_DEVICES. │
│ │ │
│ │ The total number of compute units │
│ │ specified may not exceed │
│ │ CL_DEVICE_PARTITION_MAX_COMPUTE_UNITS. │
├──────────────────────────────────────┼──────────────────────────────────────────────┤
│CL_DEVICE_PARTITION_BY_- │ Split the device into smaller │
│AFFINITY_DOMAIN │ aggregate devices containing one or │
│(cl_device_affinity_domain) │ more compute units that all share part │
│ │ of a cache hierarchy. The value │
│ │ accompanying this property may be │
│ │ drawn from the following list: │
│ │ │
│ │ CL_DEVICE_AFFINITY_DOMAIN_NUMA - Split │
│ │ the device into sub-devices comprised │
│ │ of compute units that share a NUMA │
│ │ node. │
│ │ │
│ │ CL_DEVICE_AFFINITY_DOMAIN_L4_CACHE - │
│ │ Split the device into sub-devices │
│ │ comprised of compute units that share │
│ │ a level 4 data cache. │
│ │ │
│ │ CL_DEVICE_AFFINITY_DOMAIN_L3_CACHE - │
│ │ Split the device into sub-devices │
│ │ comprised of compute units that share │
│ │ a level 3 data cache. │
│ │ │
│ │ CL_DEVICE_AFFINITY_DOMAIN_L2_CACHE - │
│ │ Split the device into sub-devices │
│ │ comprised of compute units that share │
│ │ a level 2 data cache. │
│ │ │
│ │ CL_DEVICE_AFFINITY_DOMAIN_L1_CACHE - │
│ │ Split the device into sub-devices │
│ │ comprised of compute units that share │
│ │ a level 1 data cache. │
│ │ │
│ │ CL_DEVICE_AFFINITY_DOMAIN_NEXT_PARTITIONABLE │
│ │ - Split the device along the next │
│ │ partitionable affinity domain. The │
│ │ implementation shall find the first │
│ │ level along which the device or │
│ │ sub-device may be further subdivided │
│ │ in the order NUMA, L4, L3, L2, L1, and │
│ │ partition the device into sub-devices │
│ │ comprised of compute units that share │
│ │ memory subsystems at this level. │
│ │ │
│ │ The user may determine what happened │
│ │ by calling clGetDeviceInfo(3clc) │
│ │ (CL_DEVICE_PARTITION_TYPE) on the │
│ │ sub-devices. │
└──────────────────────────────────────┴──────────────────────────────────────────────┘
num_devices
Size of memory pointed to by out_devices specified as the number of cl_device_id entries.
out_devices
The buffer where the OpenCL sub-devices will be returned. If out_devices is NULL, this argument is
ignored. If out_devices is not NULL, num_devices must be greater than or equal to the number of
sub-devices that device may be partitioned into according to the partitioning scheme specified in
properties.
num_devices_ret
Returns the number of sub-devices that device may be partitioned into according to the partitioning
scheme specified in properties. If num_devices_ret is NULL, it is ignored.
NOTES
Creates an array of sub-devices that each reference a non-intersecting set of compute units within
in_device, according to a partition scheme given by properties. The output sub-devices may be used in
every way that the root (or parent) device can be used, including creating contexts, building programs,
further calls to clCreateSubDevices and creating command-queues. When a command-queue is created against
a sub-device, the commands enqueued on the queue are executed only on the sub-device.
ERRORS
Returns CL_SUCCESS if the partition is created successfully. Otherwise, it returns a null value with the
following error values returned in errcode_ret:
• CL_INVALID_DEVICE if in_device is not valid.
• CL_INVALID_VALUE if values specified in properties are not valid or if values specified in properties
are valid but not supported by the device.
• CL_INVALID_VALUE if out_devices is not NULL and num_devices is less than the number of sub-devices
created by the partition scheme.
• CL_DEVICE_PARTITION_FAILED if the partition name is supported by the implementation but in_device
could not be further partitioned.
• CL_INVALID_DEVICE_PARTITION_COUNT if the partition name specified in properties is
CL_DEVICE_PARTITION_BY_COUNTS and the number of sub-devices requested exceeds
CL_DEVICE_PARTITION_MAX_SUB_DEVICES or the total number of compute units requested exceeds
CL_DEVICE_PARTITION_MAX_COMPUTE_UNITS for in_device, or the number of compute units requested for one
or more sub-devices is less than zero or the number of sub-devices requested exceeds
CL_DEVICE_PARTITION_MAX_COMPUTE_UNITS for in_device.
• 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.
Example
A few examples that describe how to specify partition properties in properties argument to
clCreateSubDevices are given below.
To partition a device containing 16 compute units into two sub-devices, each containing 8 compute units,
pass the following in properties:
{ CL_DEVICE_PARTITION_EQUALLY, 8, 0 }
To partition a device with four compute units into two sub-devices with one sub-device containing 3
compute units and the other sub-device 1 compute unit, pass the following in properties argument:
{ CL_DEVICE_PARTITION_BY_COUNTS, 3, 1,
CL_DEVICE_PARTITION_BY_COUNTS_LIST_END, 0 }
To split a device along the outermost cache line (if any), pass the following in properties argument:
{ CL_DEVICE_PARTITION_BY_AFFINITY_DOMAIN,
CL_DEVICE_AFFINITY_DOMAIN_NEXT_PARTITIONABLE, 0 }
SPECIFICATION
OpenCL Specification[1]
SEE ALSO
clGetDeviceInfo(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 49, section 4.3 - Partitioning a Device