OpenCL 两个向量相加
// This program implements a vector addition using OpenCL
// System includes
#include
#include
// OpenCL includes
#include
// OpenCL kernel to perform an element-wise
// add of two arrays
const char* programSource =
"__kernel void vecadd(__global int *A,__global int *B,__global int *C)\n"
"{\n"
"// Get the work-item unique ID \n"
"int idx = get_global_id(0); \n"
"// Add the corresponding locations of \n"
"// 'A' and 'B', and store the result in 'C'.\n"
" C[idx] = A[idx] + B[idx]; \n"
"}\n"
;
int main() {
// This code executes on the OpenCL host
// Host data
int *A = NULL; // Input array
int *B = NULL; // Input array
int *C = NULL; // Output array
// Elements in each array
const int elements = 2048;
// Compute the size of the data
size_t datasize = sizeof(int)*elements;
// Allocate space for input/output data
A = (int*)malloc(datasize);
B = (int*)malloc(datasize);
C = (int*)malloc(datasize);
// Initialize the input data
for(int i = 0; i < elements; i++) {
A[i] = i;
B[i] = i;
}
// Use this to check the output of each API call
cl_int status;
//-----------------------------------------------------
// STEP 1: Discover and initialize the platforms
//-----------------------------------------------------
cl_uint numPlatforms = 0;
cl_platform_id *platforms = NULL;
// Use clGetPlatformIDs() to retrieve the number of
// platforms
status = clGetPlatformIDs(0, NULL, &numPlatforms);
// Allocate enough space for each platform
platforms =
(cl_platform_id*)malloc(
numPlatforms*sizeof(cl_platform_id));
// Fill in platforms with clGetPlatformIDs()
status = clGetPlatformIDs(numPlatforms, platforms,
NULL);
//-----------------------------------------------------
// STEP 2: Discover and initialize the devices
//-----------------------------------------------------
cl_uint numDevices = 0;
cl_device_id *devices = NULL;
// Use clGetDeviceIDs() to retrieve the number of
// devices present
status = clGetDeviceIDs(
platforms[0],
CL_DEVICE_TYPE_ALL,
0,
NULL,
&numDevices);
// Allocate enough space for each device
devices =
(cl_device_id*)malloc(
numDevices*sizeof(cl_device_id));
// Fill in devices with clGetDeviceIDs()
status = clGetDeviceIDs(
platforms[0],
CL_DEVICE_TYPE_ALL,
numDevices,
devices,
NULL);
//-----------------------------------------------------
// STEP 3: Create a context
//-----------------------------------------------------
cl_context context = NULL;
// Create a context using clCreateContext() and
// associate it with the devices
context = clCreateContext(
NULL,
numDevices,
devices,
NULL,
NULL,
&status);
//-----------------------------------------------------
// STEP 4: Create a command queue
//-----------------------------------------------------
cl_command_queue cmdQueue;
// Create a command queue using clCreateCommandQueue(),
// and associate it with the device you want to execute
// on
cmdQueue = clCreateCommandQueue(
context,
devices[0],
0,
&status);
//-----------------------------------------------------
// STEP 5: Create device buffers
//-----------------------------------------------------
cl_mem bufferA; // Input array on the device
cl_mem bufferB; // Input array on the device
cl_mem bufferC; // Output array on the device
// Use clCreateBuffer() to create a buffer object (d_A)
// that will contain the data from the host array A
bufferA = clCreateBuffer(
context,
CL_MEM_READ_ONLY,
datasize,
NULL,
&status);
// Use clCreateBuffer() to create a buffer object (d_B)
// that will contain the data from the host array B
bufferB = clCreateBuffer(
context,
CL_MEM_READ_ONLY,
datasize,
NULL,
&status);
// Use clCreateBuffer() to create a buffer object (d_C)
// with enough space to hold the output data
bufferC = clCreateBuffer(
context,
CL_MEM_WRITE_ONLY,
datasize,
NULL,
&status);
//-----------------------------------------------------
// STEP 6: Write host data to device buffers
//-----------------------------------------------------
// Use clEnqueueWriteBuffer() to write input array A to
// the device buffer bufferA
status = clEnqueueWriteBuffer(
cmdQueue,
bufferA,
CL_FALSE,
0,
datasize,
A,
0,
NULL,
NULL);
// Use clEnqueueWriteBuffer() to write input array B to
// the device buffer bufferB
status = clEnqueueWriteBuffer(
cmdQueue,
bufferB,
CL_FALSE,
0,
datasize,
B,
0,
NULL,
NULL);
//-----------------------------------------------------
// STEP 7: Create and compile the program
//-----------------------------------------------------
// Create a program using clCreateProgramWithSource()
cl_program program = clCreateProgramWithSource(
context,
1,
(const char**)&programSource,
NULL,
&status);
// Build (compile) the program for the devices with
// clBuildProgram()
status = clBuildProgram(
program,
numDevices,
devices,
NULL,
NULL,
NULL);
//-----------------------------------------------------
// STEP 8: Create the kernel
//-----------------------------------------------------
cl_kernel kernel = NULL;
// Use clCreateKernel() to create a kernel from the
// vector addition function (named "vecadd")
kernel = clCreateKernel(program, "vecadd", &status);
//-----------------------------------------------------
// STEP 9: Set the kernel arguments
//-----------------------------------------------------
// Associate the input and output buffers with the
// kernel
// using clSetKernelArg()
status = clSetKernelArg(
kernel,
0,
sizeof(cl_mem),
&bufferA);
status |= clSetKernelArg(
kernel,
1,
sizeof(cl_mem),
&bufferB);
status |= clSetKernelArg(
kernel,
2,
sizeof(cl_mem),
&bufferC);
//-----------------------------------------------------
// STEP 10: Configure the work-item structure
//-----------------------------------------------------
// Define an index space (global work size) of work
// items for
// execution. A workgroup size (local work size) is not
// required,
// but can be used.
size_t globalWorkSize[1];
// There are 'elements' work-items
globalWorkSize[0] = elements;
//-----------------------------------------------------
// STEP 11: Enqueue the kernel for execution
//-----------------------------------------------------
// Execute the kernel by using
// clEnqueueNDRangeKernel().
// 'globalWorkSize' is the 1D dimension of the
// work-items
status = clEnqueueNDRangeKernel(
cmdQueue,
kernel,
1,
NULL,
globalWorkSize,
NULL,
0,
NULL,
NULL);
//-----------------------------------------------------
// STEP 12: Read the output buffer back to the host
//-----------------------------------------------------
// Use clEnqueueReadBuffer() to read the OpenCL output
// buffer (bufferC)
// to the host output array (C)
clEnqueueReadBuffer(
cmdQueue,
bufferC,
CL_TRUE,
0,
datasize,
C,
0,
NULL,
NULL);
// Verify the output
bool result = true;
for(int i = 0; i < elements; i++) {
if(C[i] != i+i) {
result = false;
break;
}
}
if(result) {
printf("Output is correct\n");
} else {
printf("Output is incorrect\n");
}
//-----------------------------------------------------
// STEP 13: Release OpenCL resources
//-----------------------------------------------------
// Free OpenCL resources
clReleaseKernel(kernel);
clReleaseProgram(program);
clReleaseCommandQueue(cmdQueue);
clReleaseMemObject(bufferA);
clReleaseMemObject(bufferB);
clReleaseMemObject(bufferC);
clReleaseContext(context);
// Free host resources
free(A);
free(B);
free(C);
free(platforms);
free(devices);
}