test_conformance/SVM/test_fine_grain_sync_buffers.cpp

//
// Copyright (c) 2017 The Khronos Group Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//    http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//
#include "common.h"

const char *find_targets_kernel[] = {

    "__kernel void find_targets(__global uint* image, uint target, volatile "
    "__global atomic_uint *numTargetsFound, volatile __global atomic_uint "
    "*targetLocations)\n"
    "{\n"
    " size_t i = get_global_id(0);\n"
    " uint index;\n"
    " if(image[i] == target) {\n"
    "   index = atomic_fetch_add_explicit(numTargetsFound, 1u, "
    "memory_order_relaxed, memory_scope_device); \n"
    "   atomic_exchange_explicit(&targetLocations[index], i, "
    "memory_order_relaxed, memory_scope_all_svm_devices); \n"
    " }\n"
    "}\n"
};


void spawnAnalysisTask(int location)
{
  //    printf("found target at location %d\n", location);
}

#define MAX_TARGETS 1024

// Goals: demonstrate use of SVM's atomics to do fine grain synchronization between the device and host.
// Concept: a device kernel is used to search an input image for regions that match a target pattern.
// The device immediately notifies the host when it finds a target (via an atomic operation that works across host and devices).
// The host is then able to spawn a task that further analyzes the target while the device continues searching for more targets.
int test_svm_fine_grain_sync_buffers(cl_device_id deviceID, cl_context c, cl_command_queue queue, int num_elements)
{
  clContextWrapper    context = NULL;
  clProgramWrapper    program = NULL;
  cl_uint     num_devices = 0;
  cl_int      err = CL_SUCCESS;
  clCommandQueueWrapper queues[MAXQ];

  err = create_cl_objects(deviceID, &find_targets_kernel[0], &context, &program, &queues[0], &num_devices, CL_DEVICE_SVM_FINE_GRAIN_BUFFER | CL_DEVICE_SVM_ATOMICS);
  if(err == 1) return 0; // no devices capable of requested SVM level, so don't execute but count test as passing.
  if(err < 0) return -1; // fail test.

  clKernelWrapper kernel = clCreateKernel(program, "find_targets", &err);
  test_error(err, "clCreateKernel failed");

  size_t num_pixels = num_elements;
  //cl_uint num_pixels = 1024*1024*32;

  cl_uint *pInputImage      = (cl_uint*) clSVMAlloc(context, CL_MEM_READ_ONLY  | CL_MEM_SVM_FINE_GRAIN_BUFFER, sizeof(cl_uint) * num_pixels, 0);
  cl_uint *pNumTargetsFound = (cl_uint*) clSVMAlloc(context, CL_MEM_READ_WRITE | CL_MEM_SVM_FINE_GRAIN_BUFFER | CL_MEM_SVM_ATOMICS, sizeof(cl_uint), 0);
  cl_int  *pTargetLocations = (cl_int* ) clSVMAlloc(context, CL_MEM_READ_WRITE | CL_MEM_SVM_FINE_GRAIN_BUFFER | CL_MEM_SVM_ATOMICS, sizeof(cl_int) * MAX_TARGETS, 0);

  cl_uint targetDescriptor = 777;
  *pNumTargetsFound = 0;
  cl_uint i;
  for(i=0; i < MAX_TARGETS; i++) pTargetLocations[i] = -1;
  for(i=0; i < num_pixels; i++) pInputImage[i] = 0;
  pInputImage[0] = targetDescriptor;
  pInputImage[3] = targetDescriptor;
  pInputImage[num_pixels - 1] = targetDescriptor;

  err |= clSetKernelArgSVMPointer(kernel, 0, pInputImage);
  err |= clSetKernelArg(kernel, 1, sizeof(cl_uint), (void*) &targetDescriptor);
  err |= clSetKernelArgSVMPointer(kernel, 2, pNumTargetsFound);
  err |= clSetKernelArgSVMPointer(kernel, 3, pTargetLocations);
  test_error(err, "clSetKernelArg failed");

  cl_event done;
  err = clEnqueueNDRangeKernel(queues[0], kernel, 1, NULL, &num_pixels, NULL, 0, NULL, &done);
  test_error(err,"clEnqueueNDRangeKernel failed");
  clFlush(queues[0]);


  i=0;
  cl_int status;
  // check for new targets, if found spawn a task to analyze target.
  do {
    err = clGetEventInfo(done,CL_EVENT_COMMAND_EXECUTION_STATUS, sizeof(cl_int), &status, NULL);
    test_error(err,"clGetEventInfo failed");
    if( AtomicLoadExplicit(&pTargetLocations[i], memory_order_relaxed) != -1)  // -1 indicates slot not used yet.
    {
      spawnAnalysisTask(pTargetLocations[i]);
      i++;
    }
  } while (status != CL_COMPLETE || AtomicLoadExplicit(&pTargetLocations[i], memory_order_relaxed) != -1);

  clReleaseEvent(done);
  clSVMFree(context, pInputImage);
  clSVMFree(context, pNumTargetsFound);
  clSVMFree(context, pTargetLocations);

  if(i != 3) return -1;
  return 0;
}