DPCT Namespace Reference

The DPCT namespace provides helper functions and macros to assist the migration of input source code. DPCT namespace helper functions are implemented in header files and are available in the include folder (include/dpct) of the SYCLomatic install path. These header files are intended to become part of your new SYCL* code generated by SYCLomatic. You can copy these header files if needed and include them with the generated code.

There are three namespaces defined:

Namespace	Description
dpct::	This namespace is used in the code generated by SYCLomatic.
dpct::detail::	This namespace is an internal implementation and should not be used in SYCL source files directly, as the API and implementations inside the dpct::detail:: namespace can be changed at any time without notice.
dpct::deprecated::	This namespace is for functionality that has been introduced for compatibility purposes, but relies on deprecated C++ features, that have been removed or will be removed in the future standards. Use of deprecated functionality in the dpct::deprecated:: namespace should be avoided.

Note

After migration, it is recommended that you continue development using SYCL and C++ standard APIs, rather than continue development based on DPCT namespace helper functions and macros.

The following sections describe different domains of helper functions and macros in more detail.

Macros

The following table lists the macros used to control the behavior of the helper functions:

Macro	Description
DPCT_USM_LEVEL_NONE	If the --usm-level=none option of SYCLomatic is used, then DPCT_USM_LEVEL_NONE is defined before DPCT namespace helper header files are included into migrated code. By default, this macro is not defined. If DPCT_USM_LEVEL_NONE is defined, corresponding helper functions guarded by this macro are active, and the resulting migrated code will use buffer-based memory functions instead of USM-based memory functions.
DPCT_NAMED_LAMBDA	If the --sycl-named-lambda option of SYCLomatic is used, then DPCT_NAMED_LAMBDA is defined before DPCT namespace helper header files are included in migrated code. By default, this macro is not defined. If DPCT_NAMED_LAMBDA is defined, corresponding helper code guarded by this macro is active and the resulting migrated code is using it.
DPCT_COMPATIBILITY_TEMP	DPCT_COMPATIBILITY_TEMP is defined as an integer number in helper header files, and is inserted into migrated code by SYCLomatic. You can replace this macro in the generated code or change the value of DPCT_COMPATIBILITY_TEMP according to your needs.

Note

Do not manually define these macros. They are automatically defined by SYCLomatic according to the options specified in the dpct command line.

Atomic Helper Functions

The atomic helper functions are available in the atomic.hpp header file. Atomic helper functions are wrappers around standard SYCL atomic operations.

Device Helper Functions

The device helper functions are available in the device.hpp header file.

The following classes are defined in the device.hpp header file:

Class	Description
device_info	device_info is used to present information enumerated by SYCL device information descriptors.
device_ext	device_ext is a subclass of SYCL device class cl::sycl::device. device_ext adds a default SYCL queue associated with the device on top of SYCL device, along with interface to query device information, and initializes device_info class.
dev_mgr	dev_mgr is a singleton, intended to manage all SYCL-capable devices available on the system (for example CPU or GPU). dev_mgr selects one of the available devices as current device, according to the behavior of SYCL default device selector. Display the current device using current_device(), and change the current device using select_device().

Find more details in the device.hpp file.

The following table lists the device helper functions:

Function	Description
get_current_device()	Returns the current device in the device manager.
get_default_queue()	Returns the default queue associated with the current device in the device manager.
get_device(unsigned int id)	Returns the device_extobject by integer id.
cpu_device	Returns the device_ext object associated with the SYCL CPU device.
get_default_context()	Returns the SYCL context of the default queue associated with the current device in device manager.

Memory Helper Functions

The following table lists SYCL buffer-based memory model helper functions:

Function

Description

Device Memory Manager (mem_mgr )

Device memory manager is a singleton, intended to assist with migration of memory API calls if a SYCL buffer-based memory model is used. It provides API to allocate and free host virtual address space bound to cl::sycl::buffer, and transform between the host virtual address and cl::sycl::buffer. By default, the mem_mgr maintains 128GB of virtual memory space. You can change virtual memory space as required by changing the value of mapped_region_size in the memory.hpp file.

The following table lists helper functions to get the SYCL buffer from host virtual address:

Function	Description
get_buffer_and_offset(const void *ptr)	Where ptris the host virtual address. This function returns the cl::sycl::buffer bound to the host virtual address, and the offset of the host virtual address in the cl::sycl::buffer.
get_buffer(const void *ptr)	Where ptris the host virtual address. Returns the sycl::buffer bound to the host virtual address.

General Helper Functions

General memory helper functions are used to assist the migration of memory API calls, like memory allocation, memory copy, and memory set, for both USM and buffer-based memory model. The following helper functions are available:

• dpct_malloc()

• dpct_free()

• dpct_memcpy()

• async_dpct_memcpy()

• dpct_memset()

• async_dpct_memset()

Find more details in the memory.hpp file.

Helper Functions Assisting Migration of Device Memory Variables

To assist with migration of variables declared with global and constant device memory attributes, the helper functions provide the following template classes:

Function	Description
global_memory	Represents a SYCL global memory variable.
constant_memory	Represents a SYCL constant memory variable.
shared_memory	Represents memory that can be accessed by host and device, in the same way as SYCL USM shared memory.

The following table lists main member functions of memory classes:

Function	Description
get_prt()	Returns memory pointer of the memory object. It is a virtual pointer when buffer-based memory model is used, and it is a device pointer when a USM memory model is used.
get_size()	Returns the size of a memory object.
get_access()	Returns the accessor to the memory object. If a USM memory model is used, this function returns a dpct_accessor_t object for the device memory object. dpct_accessor_t is a helper type, which contains the data pointer, data dimension information, and provides a method to access the memory. If a buffer-based memory model is used, this function returns cl::sycl::accessor for the device memory object.
init()	Allocates memory after a SYCL device is selected, and initializes device memory if it has initial value. This API should be called after the SYCL device is selected.

Kernel Helper Functions

Kernel helper functions provide a structure kernel_function_info to keep SYCL kernel information, and provide a utility function get_kernel_function_info() to get the kernel information.

Image Helper Functions

The image helper functions provide class wrappers to assist the migration of texture API. Find more details on image helper functions in the image.hpp file.

Wrapper	Description
Template class image_wrapper	The wrapper of cl::sycl::image. It provides methods to attach/detach 1D/2D/3D data to/from cl::sycl::image and method get_access() to return the SYCL image accessor.
Class image_accessor_ext	Wraps SYCL sampler and SYCL image accessor together. Provides the read() method to read data from the accessor.
Class image_data	Represents the data used to create a cl::sycl::image object. Supports the following data types: Matrix for 2D or 3D matrix data (see image_matrix class) Linear for 1D linear array Pitch for pitched 2D or 3D memory data (pitched_data class)
Class image_matrix	Represents 2D/3D matrix data for an image. It contains the image channel information, dimensions, size of each dimension, and the raw data pointer.
Class pitched_data	Represents the 2D/3D pitched data for an image.
Struct image_channel	Keeps image channel information; including order, data width, and type information.
Class image_info	Image sampling information; including addressing mode, filtering mode, and normalization mode.
image_wrapper operations API: create_image_wrapper()	Creates an object of the helper image class according to the parameters provided.

Intel® oneAPI DPC++ Library Specific Utility Helper functions

The helper functions provided by the header files included in dpl_utils.hpp include algorithm functions, memory functions, iterators, and a container for managing data on a device.

Algorithm Helper Functions

The algorithm helper functions are available in the dpl_extras/algorithm.h header file. Algorithm helper functions are wrappers around Intel® oneAPI DPC++ Library (oneDPL) algorithm functions.

Mask-predicated Algorithm Functions

Mask-predicated algorithm functions have parameter lists like the algorithms with the same name in the C++ standard library. These functions accept an additional iterator pointing to a set of values that indicate whether the corresponding elements of the other inputs to the function should be processed by the algorithm. The predicate provided to these functions is applied to a value in the mask, rather than the element of the input data, and if the predicate returns true the corresponding element of the input data is manipulated by the algorithm.

The mask-predicated algorithm functions in the dpl_extras/algorithm.h header file are:

• copy_if

• partition

• partition_copy

• remove_if

• remove_copy_if

• replace_if

• replace_copy_if

• stable_partition_copy

• stable_partition

• transform_if

Key-value Pair Algorithm Functions

Key-value pair algorithm functions have parameter lists like the algorithms with the same name in the C++ standard library. The functions accept two sets of input data instead of one: the first representing a set of keys and the second representing the set of values associated with each key. These algorithm functions create zip_iterators and invoke the standard algorithm provided in oneDPL so that the key-value pairs are processed as single data elements.

The key-value pair algorithm functions in the dpl_extras/algorithm.h header file are:

• unique

• unique_copy

• merge

• sort

• stable_sort

• set_difference

• set_intersection

• set_symmetric_difference

• set_union

Additional Algorithm Functions

Function	Description
partition_point	Implementation of the C++ standard library algorithm that accepts an execution policy, enabling parallel execution.
transform_if	Applies a unary operation to every element in the input for which the predicate provided returns true. A mask-predicated version of the function is also provided.
iota	Extends the C++ standard library algorithm by accepting a step in addition to the input iterators and initial value. The step is used to compute the next value in the sequence generated.
inner_product	Implementation of the C++ standard library algorithm that accepts an execution policy, enabling parallel execution. The binary operation provided for reduction must be associative and commutative.
for_each_index	Assigns each element in the input range provided the result of the unary operator invoked with the element’s index in the input range.

Memory Helper Functions

The dpl_extras/memory.h header file provides classes and functions for working with device memory.

The following table lists memory helper classes:

Class	Description
device_pointer	Pointer type that points to memory stored on a device.
device_iterator	Iterator type returned by device_vector begin and end methods.
device_reference	Reference type returned by device_vector element access operator.

The device_vector implementation that uses the device_iterator and device_reference classes is defined in dpl_extras/vector.h.

The following table list memory helper functions:

Function	Description
malloc_device	Allocates memory for use on a device.
free_device	Deallocates memory allocated with malloc_device.
device_new	Allocates memory for use on a device large enough to hold the requested number of elements of the type specified.
device_delete	Deallocates memory allocated using device_new.
get_device_pointer	Constructs a device_pointer from a raw pointer.
get_raw_pointer	Returns a raw pointer from a device_pointer instance.

oneAPI DPC++ Library Specific Utility Header Files

The following table lists utility header files specific to the oneAPI DPC++ Library:

Header File	Description
functional.h	Contains the implementation of the function objects used in the definitions of the algorithm functions described above.
iterator.h	Provides an implementation of constant_iterator, an iterator that is constructed with a value and when dereferenced will only return that value.
vector.h	Provides an implementation of device_vector, a container for managing data elements stored in device memory.

Utility Helper Functions

The following table lists header files that define utility functions:

Header File	Description
util.hpp	Common utility helper functions.
blas_utils.hpp	BLAS-specific utility helper functions.