text: //
  // 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 "harness/compat.h"
  
  #include <stdio.h>
  #include <stdlib.h>
  #include <string.h>
  #include <sys/types.h>
  #include <sys/stat.h>
  
  
  #include "procs.h"
  
  const char *barrier_kernel_code =
  "__kernel void compute_sum(__global int *a, int n, __global int *tmp_sum, __global int *sum)\n"
  "{\n"
  "    int  tid = get_local_id(0);\n"
  "    int  lsize = get_local_size(0);\n"
  "    int  i;\n"
  "\n"
  "    tmp_sum[tid] = 0;\n"
  "    for (i=tid; i<n; i+=lsize)\n"
  "        tmp_sum[tid] += a[i];\n"
  "     \n"
  "     // updated to work for any workgroup size \n"
  "    for (i=hadd(lsize,1); lsize>1; i = hadd(i,1))\n"
  "    {\n"
  "        barrier(CLK_GLOBAL_MEM_FENCE);\n"
  "        if (tid + i < lsize)\n"
  "            tmp_sum[tid] += tmp_sum[tid + i];\n"
  "         lsize = i; \n"
  "    }\n"
  "\n"
  "     //no barrier is required here because last person to write to tmp_sum[0] was tid 0 \n"
  "    if (tid == 0)\n"
  "        *sum = tmp_sum[0];\n"
  "}\n";
  
  
  static int
  verify_sum(int *inptr, int *outptr, int n)
  {
    int            r = 0;
    int         i;
  
    for (i=0; i<n; i++)
    {
          r += inptr[i];
    }
  
      if (r != outptr[0])
      {
          log_error("BARRIER test failed\n");
          return -1;
      }
  
    log_info("BARRIER test passed\n");
    return 0;
  }
  
  
  int
  test_barrier(cl_device_id device, cl_context context, cl_command_queue queue, int num_elements)
  {
      cl_mem            streams[3];
      cl_int            *input_ptr = NULL, *output_ptr = NULL;
      cl_program        program;
      cl_kernel        kernel;
      size_t    global_threads[3];
      size_t    local_threads[3];
      int                err;
      int                i;
      size_t max_local_workgroup_size[3];
      size_t max_threadgroup_size = 0;
      MTdata d;
  
      err = create_single_kernel_helper(context, &program, &kernel, 1, &barrier_kernel_code, "compute_sum" );
      test_error(err, "Failed to build kernel/program.");
  
      err = clGetKernelWorkGroupInfo(kernel, device, CL_KERNEL_WORK_GROUP_SIZE,
                                   sizeof(max_threadgroup_size), &max_threadgroup_size, NULL);
      test_error(err, "clGetKernelWorkgroupInfo failed.");
  
      err = clGetDeviceInfo(device, CL_DEVICE_MAX_WORK_ITEM_SIZES, sizeof(max_local_workgroup_size), max_local_workgroup_size, NULL);
      test_error(err, "clGetDeviceInfo failed for CL_DEVICE_MAX_WORK_ITEM_SIZES");
  
      // Pick the minimum of the device and the kernel
      if (max_threadgroup_size > max_local_workgroup_size[0])
          max_threadgroup_size = max_local_workgroup_size[0];
  
      // work group size must divide evenly into the global size
      while( num_elements % max_threadgroup_size )
          max_threadgroup_size--;
  
      input_ptr = (int*)malloc(sizeof(int) * num_elements);
      output_ptr = (int*)malloc(sizeof(int));
  
      streams[0] = clCreateBuffer(context, CL_MEM_READ_WRITE,
                                  sizeof(cl_int) * num_elements, NULL, &err);
      test_error(err, "clCreateBuffer failed.");
      streams[1] =
          clCreateBuffer(context, CL_MEM_READ_WRITE, sizeof(cl_int), NULL, &err);
      test_error(err, "clCreateBuffer failed.");
      streams[2] =
          clCreateBuffer(context, CL_MEM_READ_WRITE,
                         sizeof(cl_int) * max_threadgroup_size, NULL, &err);
      test_error(err, "clCreateBuffer failed.");
  
      d = init_genrand( gRandomSeed );
      for (i=0; i<num_elements; i++)
          input_ptr[i] = (int)get_random_float(-0x01000000, 0x01000000, d);
      free_mtdata(d);  d = NULL;
  
      err = clEnqueueWriteBuffer(queue, streams[0], CL_TRUE, 0, sizeof(cl_int)*num_elements, (void *)input_ptr, 0, NULL, NULL);
      test_error(err, "clEnqueueWriteBuffer failed.");
  
      err = clSetKernelArg(kernel, 0, sizeof streams[0], &streams[0]);
      err |= clSetKernelArg(kernel, 1, sizeof num_elements, &num_elements);
      err |= clSetKernelArg(kernel, 2, sizeof streams[2], &streams[2]);
      err |= clSetKernelArg(kernel, 3, sizeof streams[1], &streams[1]);
      test_error(err, "clSetKernelArg failed.");
  
      global_threads[0] = max_threadgroup_size;
      local_threads[0] = max_threadgroup_size;
  
      err = clEnqueueNDRangeKernel( queue, kernel, 1, NULL, global_threads, local_threads, 0, NULL, NULL );
      test_error(err, "clEnqueueNDRangeKernel failed.");
  
      err = clEnqueueReadBuffer( queue, streams[1], true, 0, sizeof(cl_int), (void *)output_ptr, 0, NULL, NULL );
      test_error(err, "clEnqueueReadBuffer failed.");
  
          err = verify_sum(input_ptr, output_ptr, num_elements);
  
  
      // cleanup
      clReleaseMemObject(streams[0]);
      clReleaseMemObject(streams[1]);
      clReleaseMemObject(streams[2]);
      clReleaseKernel(kernel);
      clReleaseProgram(program);
      free(input_ptr);
      free(output_ptr);
  
      return err;
  }
  
  
  
  
  
  