Is oclcpuexp usable for standard opencl applications?

[justxi]

I followed the install hints for oclcpuexp in the release section.
Before I compile the llvm/clang/lld with sycl support I tried an opencl example, which fails.
I check with clinfo and got the following output, there are two errors:

Number of platforms                               1
  Platform Name                                   Intel(R) OpenCL
  Platform Vendor                                 Intel(R) Corporation
  Platform Version                                OpenCL 2.1 LINUX
  Platform Profile                                FULL_PROFILE
  Platform Extensions                             cl_khr_icd cl_khr_global_int32_base_atomics cl_khr_global_int32_extended_atomics cl_khr_local_int32_base_atomics cl_khr_local_int32_extended_atomics cl_khr_int64_base_atomics cl_khr_int64_extended_atomics cl_khr_byte_addressable_store cl_khr_depth_images cl_khr_3d_image_writes cl_khr_il_program cl_intel_exec_by_local_thread cl_intel_vec_len_hint cl_intel_device_partition_by_names cl_khr_spir cl_khr_fp64 cl_khr_image2d_from_buffer 
  Platform Host timer resolution                  1ns
  Platform Extensions function suffix             INTEL

  Platform Name                                   Intel(R) OpenCL
Number of devices                                 1
  Device Name                                     Intel(R) Core(TM) i7-6700HQ CPU @ 2.60GHz
  Device Vendor                                   Intel(R) Corporation
  Device Vendor ID                                0x8086
  Device Version                                  OpenCL 2.1 (Build 0)
  Driver Version                                  2019.8.7.0
  Device OpenCL C Version                         OpenCL C 2.0 
  Device Type                                     CPU
  Device Available                                Yes
  Device Profile                                  FULL_PROFILE
  Max compute units                               8
  Max clock frequency                             2600MHz
  Device Partition                                (core)
    Max number of sub-devices                     8
    Supported partition types                     by counts, equally, by names (Intel)
  Max work item dimensions                        3
  Max work item sizes                             8192x8192x8192
  Max work group size                             8192
  Compiler Available                              Yes
  Linker Available                                Yes
  Preferred work group size multiple              <getWGsizes:519: create context : error -2>
  Max sub-groups per work group                   1
  Preferred / native vector sizes                 
    char                                                 1 / 32      
    short                                                1 / 16      
    int                                                  1 / 8       
    long                                                 1 / 4       
    half                                                 0 / 0        (n/a)
    float                                                1 / 8       
    double                                               1 / 4        (cl_khr_fp64)
  Half-precision Floating-point support           (n/a)
  Single-precision Floating-point support         (core)
    Denormals                                     Yes
    Infinity and NANs                             Yes
    Round to nearest                              Yes
    Round to zero                                 No
    Round to infinity                             No
    IEEE754-2008 fused multiply-add               No
    Support is emulated in software               No
    Correctly-rounded divide and sqrt operations  No
  Double-precision Floating-point support         (cl_khr_fp64)
    Denormals                                     Yes
    Infinity and NANs                             Yes
    Round to nearest                              Yes
    Round to zero                                 Yes
    Round to infinity                             Yes
    IEEE754-2008 fused multiply-add               Yes
    Support is emulated in software               No
  Address bits                                    64, Little-Endian
  Global memory size                              8324083712 (7.752GiB)
  Error Correction support                        No
  Max memory allocation                           2081020928 (1.938GiB)
  Unified memory for Host and Device              Yes
  Shared Virtual Memory (SVM) capabilities        (core)
    Coarse-grained buffer sharing                 Yes
    Fine-grained buffer sharing                   Yes
    Fine-grained system sharing                   Yes
    Atomics                                       Yes
  Minimum alignment for any data type             128 bytes
  Alignment of base address                       1024 bits (128 bytes)
  Preferred alignment for atomics                 
    SVM                                           64 bytes
    Global                                        64 bytes
    Local                                         0 bytes
  Max size for global variable                    65536 (64KiB)
  Preferred total size of global vars             65536 (64KiB)
  Global Memory cache type                        Read/Write
  Global Memory cache size                        262144 (256KiB)
  Global Memory cache line size                   64 bytes
  Image support                                   Yes
    Max number of samplers per kernel             480
    Max size for 1D images from buffer            130063808 pixels
    Max 1D or 2D image array size                 2048 images
    Base address alignment for 2D image buffers   64 bytes
    Pitch alignment for 2D image buffers          64 pixels
    Max 2D image size                             16384x16384 pixels
    Max 3D image size                             2048x2048x2048 pixels
    Max number of read image args                 480
    Max number of write image args                480
    Max number of read/write image args           480
  Max number of pipe args                         16
  Max active pipe reservations                    32767
  Max pipe packet size                            1024
  Local memory type                               Global
  Local memory size                               32768 (32KiB)
  Max constant buffer size                        131072 (128KiB)
  Max number of constant args                     480
  Max size of kernel argument                     3840 (3.75KiB)
  Queue properties (on host)                      
    Out-of-order execution                        Yes
    Profiling                                     Yes
    Local thread execution (Intel)                Yes
  Queue properties (on device)                    
    Out-of-order execution                        Yes
    Profiling                                     Yes
    Preferred size                                4294967295 (4GiB)
    Max size                                      4294967295 (4GiB)
  Max queues on device                            4294967295
  Max events on device                            4294967295
  Prefer user sync for interop                    No
  Profiling timer resolution                      1ns
  Execution capabilities                          
    Run OpenCL kernels                            Yes
    Run native kernels                            Yes
    Sub-group independent forward progress        No
    IL version                                    SPIR-V_1.0
    SPIR versions                                 1.2
  printf() buffer size                            1048576 (1024KiB)
  Built-in kernels                                
  Device Extensions                               cl_khr_icd cl_khr_global_int32_base_atomics cl_khr_global_int32_extended_atomics cl_khr_local_int32_base_atomics cl_khr_local_int32_extended_atomics cl_khr_int64_base_atomics cl_khr_int64_extended_atomics cl_khr_byte_addressable_store cl_khr_depth_images cl_khr_3d_image_writes cl_khr_il_program cl_intel_exec_by_local_thread cl_intel_vec_len_hint cl_intel_device_partition_by_names cl_khr_spir cl_khr_fp64 cl_khr_image2d_from_buffer 

NULL platform behavior
  clGetPlatformInfo(NULL, CL_PLATFORM_NAME, ...)  No platform
  clGetDeviceIDs(NULL, CL_DEVICE_TYPE_ALL, ...)   No platform
  clCreateContext(NULL, ...) [default]            No platform
  clCreateContext(NULL, ...) [other]              <checkNullCtx:2401: create context with device from non-default platform : error -2>
  clCreateContextFromType(NULL, CL_DEVICE_TYPE_DEFAULT)  No platform
  clCreateContextFromType(NULL, CL_DEVICE_TYPE_CPU)  No platform
  clCreateContextFromType(NULL, CL_DEVICE_TYPE_GPU)  No platform
  clCreateContextFromType(NULL, CL_DEVICE_TYPE_ACCELERATOR)  No platform
  clCreateContextFromType(NULL, CL_DEVICE_TYPE_CUSTOM)  No platform
  clCreateContextFromType(NULL, CL_DEVICE_TYPE_ALL)  No platform

The output of "lld clinfo" is:

	linux-vdso.so.1 (0x00007ffd6b889000)
	libOpenCL.so.1 => /opt/intel/oclcpuexp/x64/libOpenCL.so.1 (0x00007fe453e1c000)
	libdl.so.2 => /lib64/libdl.so.2 (0x00007fe453bbc000)
	libc.so.6 => /lib64/libc.so.6 (0x00007fe4537ec000)
	libpthread.so.0 => /lib64/libpthread.so.0 (0x00007fe4535cb000)
	/lib64/ld-linux-x86-64.so.2 (0x000055685ccd9000)

Or is this library only usable with the executable resulting from the sycl compiler?

[romanovvlad]

Before I compile the llvm/clang/lld with sycl support I tried an opencl example, which fails.

Could you please share OpenCL example you have tried?

Or is this library only usable with the executable resulting from the sycl compiler?

AFAIK it should work with regular OpenCL applications as well.

[justxi]

The example I tried is this one: https://github.com/bgaster/opencl-book-samples/tree/master/src/Chapter_2/HelloWorld

I modified it to print the error code:

Could not create GPU context, trying CPU... -1 (CL_DEVICE_NOT_FOUND)
Failed to create an OpenCL GPU or CPU context. -2 (CL_DEVICE_NOT_AVAILABLE)
Failed to create OpenCL context.

It can not create a GPU context, but I think it should be able to create a CPU context.
It works with pocl (creating a CPU context).

[AlexeySachkov]

Hi @justxi,

CL_DEVICE_NOT_AVAILABLE most likely means that by some reason CPU runtime failed to load compiler library (libOclCPUBackend if I remember name correctly). One of possible reasons here is missing dependencies: for example, this library had (and probably still has) a dependency on libtinfo.

I suggest trying to launch clinfo under LD_DEBUG=libs to see if there are any unsatisfied dependencies or try ldd on each library from CPU Runtime to directly check that all dependencies are resolved.

[justxi]

@AlexeySachkov The version I have does not depend on libtinfo. I downloaded "Intel CPU Runtime for OpenCL" from https://software.intel.com/en-us/articles/opencl-drivers which depends on libtinfo.

I tried "oclcpuexp" also on a Core i5, with the same result err="-2".
I checked all libraries with "ldd", but I could not find any missing libraries.

The sycl example I tried fails also with err="-2".

[justxi]

Is it possible to compile "oclcpuexp" from source?

[romanovvlad]

@justxi Could you please share result of:
strace ./ocl_app
?

[justxi]

@romanovvlad
Oh, the strace gave the hint... I forgot to copy "clbltfnshared.rtl".
Both libraries are working now.
Thanks you... and sorry.