Version: 2022.1
Last Updated: 04/11/2022
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Get Started with OpenMP* Offload to GPU for the Intel® oneAPI DPC++/C++ Compiler and Intel® Fortran Compiler

The OpenMP* Offload to GPU feature of the Intel® oneAPI DPC++/C++ Compiler and the Intel® Fortran Compiler compiles OpenMP source files for a wide range of accelerators. Only the

icx

and

ifx

compilers support the OpenMP Offload feature.

Before You Begin

Visit the Release Notes page for the known issues and most up-to-date information:

Intel® oneAPI DPC++/C++ Compiler Release Notes

Intel® Fortran Compiler for oneAPI Release Notes

OpenMP 5.0/5.1 Support in icx and ifx

The

icx

and

ifx

compilers support most of OpenMP 5.0 and 5.1, which includes device support for GPU target. For more details, go to the OpenMP Support section of the Intel® oneAPI DPC++/C++ Compiler Developer Guide and Reference.

OpenMP directives supported in the
icx
and
ifx
compilers for GPU and CPU:

Equivalent keywords for C++ and Fortran are provided in the list below.

allocate

atomic

barrier

critical

declare simd

declare target

declare variant

dispatch

distribute

distribute parallel for/do

distribute parallel for/do simd

distribute simd

for/do

for/do simd

loop

master

parallel

parallel for/do

parallel for/do simd

parallel loop

parallel sections

sections

simd

single

target

target data

target enter data

target exit data

target parallel

target parallel for/do

target parallel for/do simd

target parallel loop

target simd

target teams

target teams distribute

target teams distribute parallel for/do

target teams distribute parallel for/do simd

target teams distribute simd

target teams loop

target variant dispatch

(Intel extension)

target update

teams

teams distribute

teams distribute parallel for/do

teams distribute parallel for/do simd

teams distribute simd

teams loop

GPU runtime routines:

Device routines are callable from CPU to get device information and allocate device memory on GPU.

omp_get_initial_device

omp_get_interop_int

omp_get_interop_name

omp_get_interop_ptr

omp_get_interop_rc_desc

omp_get_interop_str

omp_get_interop_type_desc

omp_get_mapped_ptr

omp_get_num_devices

omp_get_num_interop_properties

omp_is_initial_device

omp_target_alloc

omp_target_alloc_device

(Intel extension)

omp_target_alloc_host

(Intel extension)

omp_target_alloc_shared

(Intel extension)

omp_target_associate_ptr

omp_target_disassociate_ptr

omp_target_free

omp_target_is_accessible

omp_target_is_present

omp_target_memcpy

omp_target_memcpy_rect

Device runtime routines callable on GPU:

omp_get_device_num

omp_get_max_threads

omp_get_num_devices

omp_get_num_procs

omp_get_num_teams

omp_get_num_threads

omp_get_team_num

omp_get_team_size

omp_get_thread_limit

omp_get_thread_num

omp_in_parallel

omp_is_initial_device

Environment variables:

OMP_DEFAULT_DEVICE

: Set default device

OMP_TARGET_OFFLOAD

: Control offload on device or host

LIBOMPTARGET_PLUGIN

: Choose OpenCL™ or Level0

LIBOMPTARGET_DEBUG

: Display debug information

Options Support for Targeting Gen9

Intel supports two new options:

-qopenmp

-fopenmp-targets=spir64

that support OpenMP and offloading execution on CPU and GPU. The

-qopenmp

option enables a middle-end that supports the transformation of OpenMP in LLVM* (but not in the Clang* front-end). The

-fopenmp-targets=spir64

option enables the compiler to generate a

x86 + SPIR64

fat binary for the GPU device binary generation.

Restrictions on Gen9 or Later Target Regions

Given that OpenMP offloading is built on top of an OpenCL runtime stack for GPU, the restrictions that apply to any OpenCL kernel functions also apply to OpenMP offloading region code. Below is a list of restrictions:

Recursive function calls (unless compile time constant expression)

Non-placement new and delete

Go-to statement restriction

thread_local

storage qualifiers

Virtual function qualifier

Function pointers (unless compile time constant expression)

Virtual functions

Exception handling

C++ standard library (e.g. only

printf

is support for GPU)

Implicit Lambda-to-Function Pointer conversion

Variadic function

Variable Length Arrays (VLA), this is not supported for the tasking model and async-offloading

Example for OpenMP Offloading

The following simple matrix multiplication code example uses OpenMP target, teams, distribute, and parallel for combined construct:

// matmul.cpp: Matrix Multiplication Example using OpenMP Offloading 
#include <stdio.h>
#include <math.h>
#include <stdlib.h>

#define MAX 128
int A[MAX][MAX], B[MAX][MAX], C[MAX][MAX], C_SERIAL[MAX][MAX];

typedef int BOOL;
typedef int TYPE;

BOOL check_result(TYPE *actual, TYPE *expected, unsigned n) {
    for (unsigned i = 0; i < n; i++) {
        if(actual[i] != expected[i]) {
            printf("Value mismatch at index = %d. Expected: %d"
                   ", Actual: %d.\n", i, expected[i], actual[i]);
            return 0;
        }
    }
    return 1;
}

void __attribute__ ((noinline)) Compute()
{
  #pragma omp target teams distribute parallel for map(to: A, B) map(tofrom: C) \
                                                   thread_limit(128)
  {
    for (int i = 0; i < MAX; i++)
    for (int j = 0; j < MAX; j++)
    for (int k = 0; k < MAX; k++)
         C[i][j] += A[i][k] * B[k][j];
  }
}

int main() {
  for (int i = 0; i < MAX; i++)
    for (int j = 0; j < MAX; j++) {
      A[i][j] = i + j - 1;
      B[i][j] = i - j + 1;
    }

  for (int i = 0; i < MAX; i++)
  for (int j = 0; j < MAX; j++)
  for (int k = 0; k < MAX; k++)
       C_SERIAL[i][j] += A[i][k] * B[k][j];

  Compute();

  if (!check_result((int*) &C[0][0], (int*) &C_SERIAL[0][0], MAX * MAX)) {
    printf("FAILED\n");
    return 1;
  }

  printf("PASSED\n");
  return 0;
}

Compilation and Run Commands

On Linux*, GCC* 4.8.5 or higher must be installed for host code compilation. This is to avoid any incompatibilities due to a changed C++ Application Binary Interface (ABI).

Compile
: Compile the source code with an

icx

icpx

, or

ifx

compiler driver that invokes GPU offloading with:

$ icx -qopenmp -fopenmp-targets=spir64 matmul_offload.c -o matmul

$ icpx -qopenmp -fopenmp-targets=spir64 matmul_offload.cpp -o matmul

$ ifx -qopenmp -fopenmp-targets=spir64 matmul_offload.f90 -o matmul

Run
: Set up the

OMP_TARGET_OFFLOAD

environment variable to force offloading or fail:

$ export OMP_TARGET_OFFLOAD=MANDATORY

The default is to fallback to host if the execution cannot be run on GPU. Below is an example:

$ ./matmul
PASSED

Enhanced Compiler Integration of GPU-Optimized LIBM Functions

In some cases, there will be multiple variants of a given math function with differing accuracy/performance tradeoffs. The compiler provides a way to choose an appropriate variant based on your compiler options. The OpenMP Offload to GPU Feature of the Intel® oneAPI DPC++/C++ Compiler and the Intel® Fortran Compiler supports all fp-models. The fp-model that is supported by Intel® C++ Compiler is migrated as well. Below is the list of math functions that are supported for Gen9 or later, based on OpenCL built-in math functions.

std::unordered_map<std::string, std::string> llvm::vpo::OCLBuiltin = {
   // float:
   {"sinf",                  "_Z3sinf"},
   {"cosf",                  "_Z3cosf"},
   {"tanf",                  "_Z3tanf"},
   {"erff",                  "_Z3erff"},
   {"expf",                  "_Z3expf"},
   {"logf",                  "_Z3logf"},
   {"log2f",                 "_Z4log2f"},
   {"powf",                  "_Z3powff"},
   {"sqrtf",                 "_Z4sqrtf"},
   {"fmaxf",                 "_Z4fmaxff"},
   {"llvm.maxnum.f32",       "_Z4fmaxff"},
   {"fminf",                 "_Z4fminff"},
   {"llvm.minnum.f32",       "_Z4fminff"},
   {"fabsf",                 "_Z4fabsf"},
   {"llvm.fabs.f32",         "_Z4fabsf"},
   {"ceilf",                 "_Z4ceilf"},
   {"llvm.ceil.f32",         "_Z4ceilf"},
   {"floorf",                "_Z5floorf"},
   {"llvm.floor.f32",        "_Z5floorf"},

   // double:
   {"sin",                   "_Z3sind"},
   {"cos",                   "_Z3cosd"},
   {"tan",                   "_Z3tand"},
   {"erf",                   "_Z3erfd"},
   {"exp",                   "_Z3expd"},
   {"log",                   "_Z3logd"},
   {"log2",                  "_Z4log2d"},
   {"pow",                   "_Z3powdd"},
   {"sqrt",                  "_Z4sqrtd"},
   {"fmax",                  "_Z4fmaxdd"},
   {"llvm.maxnum.f64",       "_Z4fmaxdd"},
   {"fmin",                  "_Z4fmindd"},
   {"llvm.minnum.f64",       "_Z4fmindd"},
   {"fabs",                  "_Z4fabsd"},
   {"llvm.fabs.f64",         "_Z4fabsd"},
   {"ceil",                  "_Z4ceild"},
   {"llvm.ceil.f64",         "_Z4ceild"},
   {"floor",                 "_Z5floord"},
   {"llvm.floor.f64",        "_Z5floord"},
   {“invsqrtf”,              “_Z5rsqrtf”},
   {“invsqrt”,               “_Z5rsqrtd”}};

The

libomptarget

runtime library has implemented performance profiling for tracking GPU kernel start, complete, and data-transfer time. Set the environment variable

LIBOMPTARGET_PLUGIN_PROFILE=T

to enable this feature. An example of the results is seen below:


================================================================================
LIBOMPTARGET_PLUGIN_PROFILE(LEVEL0) for OMP DEVICE(0) Intel(R) UHD Graphics 630 [0x3e92], Thread 0
--------------------------------------------------------------------------------
-- Kernel 0                  : __omp_offloading_3a_dca6bdd1_MAIN___l30
--------------------------------------------------------------------------------
-- Name                      :     Host Time (msec)   Device Time (msec)
-- Compiling                 :             2632.679             2632.679
-- DataAlloc                 :               11.350               11.350
-- DataRead (Device to Host) :                2.633                2.633
-- DataWrite (Host to Device):                8.398                8.398
-- Kernel 0                  :             5279.800             5258.379
-- OffloadEntriesInit        :                2.731                2.731
-- Total                     :             7937.591             7916.170
================================================================================

Early Integration of GPU-specific Debug Information

To provide GPU specific debug, support for the environment variable:

export LIBOMPTARGET_DEBUG=1

was added. This allows for dumping offloading runtime debugging information. Its default value is 0, which indicates no offloading runtime debugging information dump. The following example uses the previous matrix multiplication example to show GPU-specific debug information:



$ icx -v
Intel(R) oneAPI DPC++/C++ Compiler 2021.4.0 …
$ icx -qopenmp -fopenmp-targets=spir64 matmul.cpp -o matmul
$ export LIBOMPTARGET_DEBUG=1 
$ ./matmul 
Libomptarget --> Init target library!
Libomptarget --> Initialized OMPT
Libomptarget --> Loading RTLs...
Libomptarget --> Loading library 'libomptarget.rtl.level0.so'...
Target LEVEL0 RTL --> Init Level0 plugin!
Target LEVEL0 RTL --> omp_get_thread_limit() returned 2147483647
Target LEVEL0 RTL --> omp_get_max_teams() returned 0
Libomptarget --> Successfully loaded library 'libomptarget.rtl.level0.so'!
Target LEVEL0 RTL --> Looking for Level0 devices...
Target LEVEL0 RTL --> Initialized L0, API 10002
Target LEVEL0 RTL --> Found 1 driver(s)!
Target LEVEL0 RTL --> Found copy command queue for device 0x0000000000e4bc00, ordinal = 1
Target LEVEL0 RTL --> Found a GPU device, Name = Intel(R) Iris(R) Xe MAX Graphics [0x4905]
Target LEVEL0 RTL --> Found a GPU device, Name = Intel(R) UHD Graphics 630 [0x3e98]
Target LEVEL0 RTL --> No subdevices are found for device 0x0000000000e4bc00 at level 0
Target LEVEL0 RTL --> Could not find multi-context command queue group for device 0x0000000000e4bc00
Target LEVEL0 RTL --> No subdevices are found for device 0x0000000000ea31e0 at level 0
Target LEVEL0 RTL --> Could not find multi-context command queue group for device 0x0000000000ea31e0
Target LEVEL0 RTL --> Found 2 root devices, 2 total devices.
Target LEVEL0 RTL --> List of devices (DeviceID[.SubDeviceLevel.SubDeviceID])
Target LEVEL0 RTL --> -- 0
Target LEVEL0 RTL --> -- 1
Target LEVEL0 RTL --> Driver API version is 10001
Target LEVEL0 RTL --> Interop property IDs, Names, Descriptions
Target LEVEL0 RTL --> -- 0, device_num_eus, intptr_t, total number of EUs
Target LEVEL0 RTL --> -- 1, device_num_threads_per_eu, intptr_t, number of threads per EU
Target LEVEL0 RTL --> -- 2, device_eu_simd_width, intptr_t, physical EU simd width
Target LEVEL0 RTL --> -- 3, device_num_eus_per_subslice, intptr_t, number of EUs per sub-slice
Target LEVEL0 RTL --> -- 4, device_num_subslices_per_slice, intptr_t, number of sub-slices per slice
Target LEVEL0 RTL --> -- 5, device_num_slices, intptr_t, number of slices
Target LEVEL0 RTL --> Returning 2 top-level devices
Libomptarget --> Registering RTL libomptarget.rtl.level0.so supporting 2 devices!
Libomptarget --> Optional interface: __tgt_rtl_data_alloc_base
Libomptarget --> Optional interface: __tgt_rtl_data_alloc_user
Libomptarget --> Optional interface: __tgt_rtl_data_alloc_explicit
Libomptarget --> Optional interface: __tgt_rtl_data_alloc_managed
Libomptarget --> Optional interface: __tgt_rtl_data_submit_nowait
Libomptarget --> Optional interface: __tgt_rtl_data_retrieve_nowait
Libomptarget --> Optional interface: __tgt_rtl_create_offload_queue
Libomptarget --> Optional interface: __tgt_rtl_release_offload_queue
Libomptarget --> Optional interface: __tgt_rtl_get_platform_handle
Libomptarget --> Optional interface: __tgt_rtl_set_device_handle
Libomptarget --> Optional interface: __tgt_rtl_get_context_handle
Libomptarget --> Optional interface: __tgt_rtl_init_ompt
Libomptarget --> Optional interface: __tgt_rtl_is_device_accessible_ptr
Libomptarget --> Optional interface: __tgt_rtl_manifest_data_for_region
Libomptarget --> Optional interface: __tgt_rtl_push_subdevice
Libomptarget --> Optional interface: __tgt_rtl_pop_subdevice
Libomptarget --> Optional interface: __tgt_rtl_add_build_options
Libomptarget --> Optional interface: __tgt_rtl_is_supported_device
Libomptarget --> Optional interface: __tgt_rtl_deinit
Libomptarget --> Optional interface: __tgt_rtl_create_interop
Libomptarget --> Optional interface: __tgt_rtl_release_interop
Libomptarget --> Optional interface: __tgt_rtl_use_interop
Libomptarget --> Optional interface: __tgt_rtl_get_num_interop_properties
Libomptarget --> Optional interface: __tgt_rtl_get_interop_property_value
Libomptarget --> Optional interface: __tgt_rtl_get_interop_property_info
Libomptarget --> Optional interface: __tgt_rtl_get_interop_rc_desc
Libomptarget --> Optional interface: __tgt_rtl_get_num_sub_devices
Libomptarget --> Optional interface: __tgt_rtl_is_accessible_addr_range
Libomptarget --> Optional interface: __tgt_rtl_run_target_team_nd_region
Libomptarget --> Optional interface: __tgt_rtl_run_target_region_nowait
Libomptarget --> Optional interface: __tgt_rtl_run_target_team_region_nowait
Libomptarget --> Optional interface: __tgt_rtl_run_target_team_nd_region_nowait
Target LEVEL0 RTL --> Initialized OMPT
Libomptarget --> Loading library 'libomptarget.rtl.opencl.so'...
Target OPENCL RTL --> Init OpenCL plugin!
Target OPENCL RTL --> omp_get_thread_limit() returned 2147483647
Target OPENCL RTL --> omp_get_max_teams() returned 0
Target OPENCL RTL --> Target device type is set to GPU
Libomptarget --> Successfully loaded library 'libomptarget.rtl.opencl.so'!
Target OPENCL RTL --> Start initializing OpenCL
Target OPENCL RTL --> Platform OpenCL 3.0  has 1 Devices
Target OPENCL RTL --> Extension clGetMemAllocInfoINTEL is found.
Target OPENCL RTL --> Extension clHostMemAllocINTEL is found.
Target OPENCL RTL --> Extension clDeviceMemAllocINTEL is found.
Target OPENCL RTL --> Extension clSharedMemAllocINTEL is found.
Target OPENCL RTL --> Extension clMemFreeINTEL is found.
Target OPENCL RTL --> Extension clSetKernelArgMemPointerINTEL is found.
Target OPENCL RTL --> Extension clEnqueueMemcpyINTEL is found.
Target OPENCL RTL --> Extension clGetDeviceGlobalVariablePointerINTEL is found.
Target OPENCL RTL --> Extension clGetKernelSuggestedLocalWorkSizeINTEL is found.
Target OPENCL RTL --> Extension clSetProgramSpecializationConstant is found.
Target OPENCL RTL --> Platform OpenCL 3.0  has 1 Devices
Target OPENCL RTL --> Extension clGetMemAllocInfoINTEL is found.
Target OPENCL RTL --> Extension clHostMemAllocINTEL is found.
Target OPENCL RTL --> Extension clDeviceMemAllocINTEL is found.
Target OPENCL RTL --> Extension clSharedMemAllocINTEL is found.
Target OPENCL RTL --> Extension clMemFreeINTEL is found.
Target OPENCL RTL --> Extension clSetKernelArgMemPointerINTEL is found.
Target OPENCL RTL --> Extension clEnqueueMemcpyINTEL is found.
Target OPENCL RTL --> Extension clGetDeviceGlobalVariablePointerINTEL is found.
Target OPENCL RTL --> Extension clGetKernelSuggestedLocalWorkSizeINTEL is found.
Target OPENCL RTL --> Extension clSetProgramSpecializationConstant is found.
Target OPENCL RTL --> Device 0: Intel(R) Iris(R) Xe MAX Graphics [0x4905]
Target OPENCL RTL --> Number of execution units on the device is 96
Target OPENCL RTL --> Maximum work group size for the device is 512
Target OPENCL RTL --> Maximum memory allocation size is 4044357632
Target OPENCL RTL --> Addressing mode is 64 bit
Target OPENCL RTL --> Device local mem size: 65536
Target OPENCL RTL --> Device 1: Intel(R) UHD Graphics 630 [0x3e98]
Target OPENCL RTL --> Number of execution units on the device is 24
Target OPENCL RTL --> Maximum work group size for the device is 256
Target OPENCL RTL --> Maximum memory allocation size is 4294959104
Target OPENCL RTL --> Addressing mode is 64 bit
Target OPENCL RTL --> Device local mem size: 65536
Libomptarget --> Registering RTL libomptarget.rtl.opencl.so supporting 2 devices!
Libomptarget --> Optional interface: __tgt_rtl_data_alloc_base
Libomptarget --> Optional interface: __tgt_rtl_data_alloc_user
Libomptarget --> Optional interface: __tgt_rtl_data_alloc_explicit
Libomptarget --> Optional interface: __tgt_rtl_data_alloc_managed
Libomptarget --> Optional interface: __tgt_rtl_data_submit_nowait
Libomptarget --> Optional interface: __tgt_rtl_data_retrieve_nowait
Libomptarget --> Optional interface: __tgt_rtl_create_offload_queue
Libomptarget --> Optional interface: __tgt_rtl_release_offload_queue
Libomptarget --> Optional interface: __tgt_rtl_get_device_name
Libomptarget --> Optional interface: __tgt_rtl_get_platform_handle
Libomptarget --> Optional interface: __tgt_rtl_set_device_handle
Libomptarget --> Optional interface: __tgt_rtl_get_context_handle
Libomptarget --> Optional interface: __tgt_rtl_get_data_alloc_info
Libomptarget --> Optional interface: __tgt_rtl_init_ompt
Libomptarget --> Optional interface: __tgt_rtl_is_device_accessible_ptr
Libomptarget --> Optional interface: __tgt_rtl_manifest_data_for_region
Libomptarget --> Optional interface: __tgt_rtl_add_build_options
Libomptarget --> Optional interface: __tgt_rtl_is_supported_device
Libomptarget --> Optional interface: __tgt_rtl_deinit
Libomptarget --> Optional interface: __tgt_rtl_create_interop
Libomptarget --> Optional interface: __tgt_rtl_release_interop
Libomptarget --> Optional interface: __tgt_rtl_use_interop
Libomptarget --> Optional interface: __tgt_rtl_get_num_interop_properties
Libomptarget --> Optional interface: __tgt_rtl_get_interop_property_value
Libomptarget --> Optional interface: __tgt_rtl_get_interop_property_info
Libomptarget --> Optional interface: __tgt_rtl_get_interop_rc_desc
Libomptarget --> Optional interface: __tgt_rtl_is_accessible_addr_range
Libomptarget --> Optional interface: __tgt_rtl_run_target_team_nd_region
Libomptarget --> Optional interface: __tgt_rtl_run_target_region_nowait
Libomptarget --> Optional interface: __tgt_rtl_run_target_team_region_nowait
Libomptarget --> Optional interface: __tgt_rtl_run_target_team_nd_region_nowait
Target OPENCL RTL --> Initialized OMPT
Libomptarget --> Loading library 'libomptarget.rtl.ppc64.so'...
Libomptarget --> Unable to load library 'libomptarget.rtl.ppc64.so': libomptarget.rtl.ppc64.so: cannot open shared object file: No such file or directory!
Libomptarget --> Loading library 'libomptarget.rtl.x86_64.so'...
Libomptarget --> Unable to load library 'libomptarget.rtl.x86_64.so': libffi.so.6: cannot open shared object file: No such file or directory!
Libomptarget --> Loading library 'libomptarget.rtl.cuda.so'...
Libomptarget --> Unable to load library 'libomptarget.rtl.cuda.so': libomptarget.rtl.cuda.so: cannot open shared object file: No such file or directory!
Libomptarget --> Loading library 'libomptarget.rtl.aarch64.so'...
Libomptarget --> Unable to load library 'libomptarget.rtl.aarch64.so': libomptarget.rtl.aarch64.so: cannot open shared object file: No such file or directory!
Libomptarget --> Loading library 'libomptarget.rtl.ve.so'...
Libomptarget --> Unable to load library 'libomptarget.rtl.ve.so': libomptarget.rtl.ve.so: cannot open shared object file: No such file or directory!
Libomptarget --> Loading library 'libomptarget.rtl.amdgpu.so'...
Libomptarget --> Unable to load library 'libomptarget.rtl.amdgpu.so': libomptarget.rtl.amdgpu.so: cannot open shared object file: No such file or directory!
Libomptarget --> Loading library 'libomptarget.rtl.rpc.so'...
Libomptarget --> Unable to load library 'libomptarget.rtl.rpc.so': libomptarget.rtl.rpc.so: cannot open shared object file: No such file or directory!
Libomptarget --> RTLs loaded!
Target LEVEL0 RTL --> Target binary is a valid oneAPI OpenMP image.
Libomptarget --> Image 0x00000000004021d0 is compatible with RTL libomptarget.rtl.level0.so!
Libomptarget --> RTL 0x0000000000cd6f20 has index 0!
Libomptarget --> Registering image 0x00000000004021d0 with RTL libomptarget.rtl.level0.so!
Libomptarget --> Done registering entries!
Libomptarget --> Entering target region with entry point 0x00000000004020b0 and device Id 0
Libomptarget --> Call to omp_get_num_devices returning 2
Libomptarget --> Default TARGET OFFLOAD policy is now mandatory (devices were found)
Libomptarget --> Call to omp_get_num_devices returning 2
Libomptarget --> Call to omp_get_num_devices returning 2
Libomptarget --> Call to omp_get_initial_device returning 2
Libomptarget --> Checking whether device 0 is ready.
Libomptarget --> Is the device 0 (local ID 0) initialized? 0
Target LEVEL0 RTL --> Initialize requires flags to 1
Target LEVEL0 RTL --> Allocated a host memory object 0x0000149189791000
Target LEVEL0 RTL --> Initialized host memory pool for device 0x0000000000000000: AllocMax = 1048576, Capacity = 4, PoolSizeMax = 268435456
Target LEVEL0 RTL --> Allocated a shared memory object 0x0000149189791000
Target LEVEL0 RTL --> Initialized shared memory pool for device 0x0000000000e4bc00: AllocMax = 65536, Capacity = 1, PoolSizeMax = 268435456
Target LEVEL0 RTL --> Allocated a shared memory object 0x0000149189791000
Target LEVEL0 RTL --> Initialized shared memory pool for device 0x0000000000ea31e0: AllocMax = 1048576, Capacity = 4, PoolSizeMax = 268435456
Target LEVEL0 RTL --> Allocated a device memory object 0x00003b7070bc0000
Target LEVEL0 RTL --> Initialized device memory pool for device 0x0000000000e4bc00: AllocMax = 1048576, Capacity = 4, PoolSizeMax = 268435456
Target LEVEL0 RTL --> Allocated a device memory object 0xffffd556aa7e0000
Target LEVEL0 RTL --> Initialized device memory pool for device 0x0000000000ea31e0: AllocMax = 1048576, Capacity = 4, PoolSizeMax = 268435456
Target LEVEL0 RTL --> Initialized Level0 device 0
Libomptarget --> Device 0 is ready to use.
Target LEVEL0 RTL --> Device 0: Loading binary from 0x00000000004021d0
Target LEVEL0 RTL --> Expecting to have 1 entries defined
Target LEVEL0 RTL --> Base L0 module compilation options: -cl-std=CL2.0
Target LEVEL0 RTL --> Created module from image #0.
Target LEVEL0 RTL --> Kernel 0: Entry = 0x00000000004020b0, Name = __omp_offloading_42_d74c0b80__Z7Computev_l25, NumArgs = 5, Handle = 0x000000000186dff0
Target LEVEL0 RTL --> Looking up device global variable '__omp_spirv_program_data' of size 48 bytes on device 0.
Target LEVEL0 RTL --> Global variable lookup succeeded.
Target LEVEL0 RTL --> Created a command list 0x0000000001c94a50 for device 0.
Target LEVEL0 RTL --> Created a command queue 0x00000000016a2260 for device 0.
Libomptarget --> Entry  0: Base=0x00000000004651a0, Begin=0x00000000004651a0, Size=65536, Type=0x23, Name=unknown
Libomptarget --> Entry  1: Base=0x00000000004451a0, Begin=0x00000000004451a0, Size=65536, Type=0x21, Name=unknown
Libomptarget --> Entry  2: Base=0x00000000004551a0, Begin=0x00000000004551a0, Size=65536, Type=0x21, Name=unknown
Libomptarget --> Entry  3: Base=0x0000000000000000, Begin=0x0000000000000000, Size=0, Type=0x120, Name=unknown
Libomptarget --> Entry  4: Base=0x000000000000007f, Begin=0x000000000000007f, Size=0, Type=0x120, Name=unknown
Libomptarget --> Entry  5: Base=0x00007ffc42aa36a0, Begin=0x00007ffc42aa36a0, Size=32, Type=0x800, Name=unknown
Libomptarget --> Looking up mapping(HstPtrBegin=0x00000000004651a0, Size=65536)...
Target LEVEL0 RTL --> Ptr 0x00000000004651a0 is not a device accessible memory pointer.
Target LEVEL0 RTL --> Allocated a device memory object 0x00003b7070b70000
Target LEVEL0 RTL --> New block allocation for device memory pool: base = 0x00003b7070b70000, size = 262144, pool size = 262144
Target LEVEL0 RTL --> Allocated target memory 0x00003b7070b70000 (Base: 0x00003b7070b70000, Size: 65536) from memory pool for host ptr 0x00000000004651a0
Libomptarget --> Creating new map entry with HstPtrBegin=0x00000000004651a0, TgtPtrBegin=0x00003b7070b70000, Size=65536, RefCount=1, Name=unknown
Libomptarget --> There are 65536 bytes allocated at target address 0x00003b7070b70000 - is new
Libomptarget --> Moving 65536 bytes (hst:0x00000000004651a0) -> (tgt:0x00003b7070b70000)
Target LEVEL0 RTL --> Copy Engine is used for data transfer
Target LEVEL0 RTL --> Copied 65536 bytes (hst:0x00000000004651a0) -> (tgt:0x00003b7070b70000)
Libomptarget --> Looking up mapping(HstPtrBegin=0x00000000004451a0, Size=65536)...
Target LEVEL0 RTL --> Ptr 0x00000000004451a0 is not a device accessible memory pointer.
Target LEVEL0 RTL --> Allocated target memory 0x00003b7070b80000 (Base: 0x00003b7070b80000, Size: 65536) from memory pool for host ptr 0x00000000004451a0
Libomptarget --> Creating new map entry with HstPtrBegin=0x00000000004451a0, TgtPtrBegin=0x00003b7070b80000, Size=65536, RefCount=1, Name=unknown
Libomptarget --> There are 65536 bytes allocated at target address 0x00003b7070b80000 - is new
Libomptarget --> Moving 65536 bytes (hst:0x00000000004451a0) -> (tgt:0x00003b7070b80000)
Target LEVEL0 RTL --> Copy Engine is used for data transfer
Target LEVEL0 RTL --> Copied 65536 bytes (hst:0x00000000004451a0) -> (tgt:0x00003b7070b80000)
Libomptarget --> Looking up mapping(HstPtrBegin=0x00000000004551a0, Size=65536)...
Target LEVEL0 RTL --> Ptr 0x00000000004551a0 is not a device accessible memory pointer.
Target LEVEL0 RTL --> Allocated target memory 0x00003b7070b90000 (Base: 0x00003b7070b90000, Size: 65536) from memory pool for host ptr 0x00000000004551a0
Libomptarget --> Creating new map entry with HstPtrBegin=0x00000000004551a0, TgtPtrBegin=0x00003b7070b90000, Size=65536, RefCount=1, Name=unknown
Libomptarget --> There are 65536 bytes allocated at target address 0x00003b7070b90000 - is new
Libomptarget --> Moving 65536 bytes (hst:0x00000000004551a0) -> (tgt:0x00003b7070b90000)
Target LEVEL0 RTL --> Copy Engine is used for data transfer
Target LEVEL0 RTL --> Copied 65536 bytes (hst:0x00000000004551a0) -> (tgt:0x00003b7070b90000)
Libomptarget --> Looking up mapping(HstPtrBegin=0x00000000004651a0, Size=65536)...
Libomptarget --> Mapping exists with HstPtrBegin=0x00000000004651a0, TgtPtrBegin=0x00003b7070b70000, Size=65536, RefCount=1 (update suppressed)
Libomptarget --> Obtained target argument (Begin: 0x00003b7070b70000, Offset: 0) from host pointer 0x00000000004651a0
Libomptarget --> Looking up mapping(HstPtrBegin=0x00000000004451a0, Size=65536)...
Libomptarget --> Mapping exists with HstPtrBegin=0x00000000004451a0, TgtPtrBegin=0x00003b7070b80000, Size=65536, RefCount=1 (update suppressed)
Libomptarget --> Obtained target argument (Begin: 0x00003b7070b80000, Offset: 0) from host pointer 0x00000000004451a0
Libomptarget --> Looking up mapping(HstPtrBegin=0x00000000004551a0, Size=65536)...
Libomptarget --> Mapping exists with HstPtrBegin=0x00000000004551a0, TgtPtrBegin=0x00003b7070b90000, Size=65536, RefCount=1 (update suppressed)
Libomptarget --> Obtained target argument (Begin: 0x00003b7070b90000, Offset: 0) from host pointer 0x00000000004551a0
Libomptarget --> Forwarding first-private value 0x0000000000000000 to the target construct
Libomptarget --> Forwarding first-private value 0x000000000000007f to the target construct
Libomptarget --> Launching target execution __omp_offloading_42_d74c0b80__Z7Computev_l25 with pointer 0x0000000001091720 (index=0).
Libomptarget --> Manifesting used target pointers:
Target LEVEL0 RTL --> Executing a kernel 0x0000000001091720...
Target LEVEL0 RTL --> Kernel argument 0 (value: 0x00003b7070b70000) was set successfully
Target LEVEL0 RTL --> Kernel argument 1 (value: 0x00003b7070b80000) was set successfully
Target LEVEL0 RTL --> Kernel argument 2 (value: 0x00003b7070b90000) was set successfully
Target LEVEL0 RTL --> Kernel argument 3 (value: 0x0000000000000000) was set successfully
Target LEVEL0 RTL --> Kernel argument 4 (value: 0x000000000000007f) was set successfully
Target LEVEL0 RTL --> Setting indirect access flags 0x0000000000000000
Target LEVEL0 RTL --> Assumed kernel SIMD width is 16
Target LEVEL0 RTL --> Preferred group size is multiple of 32
Target LEVEL0 RTL --> Max group size is set to 128 (thread_limit clause)
Target LEVEL0 RTL --> Level 0: Lb = 0, Ub = 127, Stride = 1
Target LEVEL0 RTL --> Group sizes = {128, 1, 1}
Target LEVEL0 RTL --> Group counts = {1, 1, 1}
Target LEVEL0 RTL --> Created a command list 0x0000000001d040c0 for device 0.
Target LEVEL0 RTL --> Created a command queue 0x00000000011179e0 for device 0.
Target LEVEL0 RTL --> Executed a kernel 0x0000000001091720
Libomptarget --> Looking up mapping(HstPtrBegin=0x00000000004551a0, Size=65536)...
Libomptarget --> Mapping exists with HstPtrBegin=0x00000000004551a0, TgtPtrBegin=0x00003b7070b90000, Size=65536, RefCount=1 (deferred final decrement)
Libomptarget --> There are 65536 bytes allocated at target address 0x00003b7070b90000 - is last
Libomptarget --> Looking up mapping(HstPtrBegin=0x00000000004451a0, Size=65536)...
Libomptarget --> Mapping exists with HstPtrBegin=0x00000000004451a0, TgtPtrBegin=0x00003b7070b80000, Size=65536, RefCount=1 (deferred final decrement)
Libomptarget --> There are 65536 bytes allocated at target address 0x00003b7070b80000 - is last
Libomptarget --> Looking up mapping(HstPtrBegin=0x00000000004651a0, Size=65536)...
Libomptarget --> Mapping exists with HstPtrBegin=0x00000000004651a0, TgtPtrBegin=0x00003b7070b70000, Size=65536, RefCount=1 (deferred final decrement)
Libomptarget --> There are 65536 bytes allocated at target address 0x00003b7070b70000 - is last
Libomptarget --> Moving 65536 bytes (tgt:0x00003b7070b70000) -> (hst:0x00000000004651a0)
Target LEVEL0 RTL --> Copy Engine is used for data transfer
Target LEVEL0 RTL --> Copied 65536 bytes (tgt:0x00003b7070b70000) -> (hst:0x00000000004651a0)
Target LEVEL0 RTL --> Ptr 0x00000000004551a0 is not a device accessible memory pointer.
Libomptarget --> Looking up mapping(HstPtrBegin=0x00000000004551a0, Size=65536)...
Libomptarget --> Deleting tgt data 0x00003b7070b90000 of size 65536
Target LEVEL0 RTL --> Returned device memory 0x00003b7070b90000 to memory pool
Libomptarget --> Removing map entry with HstPtrBegin=0x00000000004551a0, TgtPtrBegin=0x00003b7070b90000, Size=65536, Name=unknown
Target LEVEL0 RTL --> Ptr 0x00000000004451a0 is not a device accessible memory pointer.
Libomptarget --> Looking up mapping(HstPtrBegin=0x00000000004451a0, Size=65536)...
Libomptarget --> Deleting tgt data 0x00003b7070b80000 of size 65536
Target LEVEL0 RTL --> Returned device memory 0x00003b7070b80000 to memory pool
Libomptarget --> Removing map entry with HstPtrBegin=0x00000000004451a0, TgtPtrBegin=0x00003b7070b80000, Size=65536, Name=unknown
Target LEVEL0 RTL --> Ptr 0x00000000004651a0 is not a device accessible memory pointer.
Libomptarget --> Looking up mapping(HstPtrBegin=0x00000000004651a0, Size=65536)...
Libomptarget --> Deleting tgt data 0x00003b7070b70000 of size 65536
Target LEVEL0 RTL --> Returned device memory 0x00003b7070b70000 to memory pool
Libomptarget --> Removing map entry with HstPtrBegin=0x00000000004651a0, TgtPtrBegin=0x00003b7070b70000, Size=65536, Name=unknown
Target OPENCL RTL --> Closed RTL successfully
Libomptarget --> Unloading target library!
Target LEVEL0 RTL --> Target binary is a valid oneAPI OpenMP image.
Libomptarget --> Image 0x00000000004021d0 is compatible with RTL 0x0000000000cd6f20!
Libomptarget --> Unregistered image 0x00000000004021d0 from RTL 0x0000000000cd6f20!
Libomptarget --> Done unregistering images!
Libomptarget --> Removing translation table for descriptor 0x00000000004021b0
Libomptarget --> Done unregistering library!
Libomptarget --> Deinit target library!
Target LEVEL0 RTL --> Deinit Level0 plugin!
Target LEVEL0 RTL --> Memory usage for host memory, device 0:
Target LEVEL0 RTL --> -- Allocator:       Native,         Pool
Target LEVEL0 RTL --> -- Requested:            0,            0
Target LEVEL0 RTL --> -- Allocated:            0,            0
Target LEVEL0 RTL --> -- Freed    :            0,            0
Target LEVEL0 RTL --> -- InUse    :            0,            0
Target LEVEL0 RTL --> -- PeakUse  :            0,            0
Target LEVEL0 RTL --> -- NumAllocs:            0,            0
Target LEVEL0 RTL --> Memory usage for shared memory, device 0:
Target LEVEL0 RTL --> -- Allocator:       Native,         Pool
Target LEVEL0 RTL --> -- Requested:            0,            0
Target LEVEL0 RTL --> -- Allocated:            0,            0
Target LEVEL0 RTL --> -- Freed    :            0,            0
Target LEVEL0 RTL --> -- InUse    :            0,            0
Target LEVEL0 RTL --> -- PeakUse  :            0,            0
Target LEVEL0 RTL --> -- NumAllocs:            0,            0
Target LEVEL0 RTL --> Memory usage for shared memory, device 1:
Target LEVEL0 RTL --> -- Allocator:       Native,         Pool
Target LEVEL0 RTL --> -- Requested:            0,            0
Target LEVEL0 RTL --> -- Allocated:            0,            0
Target LEVEL0 RTL --> -- Freed    :            0,            0
Target LEVEL0 RTL --> -- InUse    :            0,            0
Target LEVEL0 RTL --> -- PeakUse  :            0,            0
Target LEVEL0 RTL --> -- NumAllocs:            0,            0
Target LEVEL0 RTL --> Memory usage for device memory, device 0:
Target LEVEL0 RTL --> -- Allocator:       Native,         Pool
Target LEVEL0 RTL --> -- Requested:       262144,       196608
Target LEVEL0 RTL --> -- Allocated:       262144,       196608
Target LEVEL0 RTL --> -- Freed    :       262144,       196608
Target LEVEL0 RTL --> -- InUse    :            0,            0
Target LEVEL0 RTL --> -- PeakUse  :       262144,       196608
Target LEVEL0 RTL --> -- NumAllocs:            1,            3
Target LEVEL0 RTL --> Memory usage for device memory, device 1:
Target LEVEL0 RTL --> -- Allocator:       Native,         Pool
Target LEVEL0 RTL --> -- Requested:            0,            0
Target LEVEL0 RTL --> -- Allocated:            0,            0
Target LEVEL0 RTL --> -- Freed    :            0,            0
Target LEVEL0 RTL --> -- InUse    :            0,            0
Target LEVEL0 RTL --> -- PeakUse  :            0,            0
Target LEVEL0 RTL --> -- NumAllocs:            0,            0
Target LEVEL0 RTL --> Closed RTL successfully
Target OPENCL RTL --> Deinit OpenCL plugin!
PASSED

Programming with an Intel® GPU is similar to programming with other GPUs. Different GPU (micro) architectures perform differently. Re-tuning a code for a new (micro) architecture is harder than functional migration. Intel is working towards providing compilers, libraries, and tools to reduce the burden of the latter, but this does not eliminate the need for performance optimizations.

Find More

Document	Description and links
OpenMP 5.0 and 5.1 specification PDFs	The OpenMP API 5.0 Specification and OpenMP API 5.1 Specification describe how OpenMP offloading can be used for devices.
The GNU C/C++ Library	Using Dual ABI
SC'16 and SC'17 LLVM-HPC workshop papers on OpenMP support	LLVM Compiler Implementation for Explicit Parallelization and SIMD Vectorization. LLVM-HPC@SC 2017: 4:1–4:11 LLVM Framework and IR Extensions for Parallelization, SIMD Vectorization and Offloading. LLVM-HPC@SC 2016: 21–31
Layers for Yocto* Project	Add oneAPI components to a Yocto project build using the meta-intel layers.

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Get Started with OpenMP* Offload to GPU for the Intel® oneAPI DPC++/C++ Compiler and Intel® Fortran Compiler

Before You Begin

OpenMP 5.0/5.1 Support in icx and ifx

Options Support for Targeting Gen9

Restrictions on Gen9 or Later Target Regions

Example for OpenMP Offloading

Compilation and Run Commands

Enhanced Compiler Integration of GPU-Optimized LIBM Functions

Early Integration of GPU-specific Debug Information

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Get Started with OpenMP* Offload to GPU for the Intel® oneAPI DPC++/C++ Compiler and Intel® Fortran Compiler

Before You Begin

OpenMP 5.0/5.1 Support in icx and ifx

Options Support for Targeting Gen9

Restrictions on Gen9 or Later Target Regions

Example for OpenMP Offloading

Compilation and Run Commands

Enhanced Compiler Integration of GPU-Optimized LIBM Functions

Early Integration of GPU-specific Debug Information

Find More

Notices and Disclaimers

Product and Performance Information