I’m having a problem when I try to run the reduction program from the OpenCL in Action’s sources.
Im using Visual Studio 2008. This is the error:
Unhandled exception in 0x013526a7 in Reduction.exe: 0xC00000FD: Stack
overflow.
And in the asm file the cursor is to
test dword ptr [eax],eax ; probe page.
I tried to debug it, but when I put a breakpoint in the main function, the debugging starts, but the program does not keep running.
I don’t know what is the really problem.
These are the source files:
reduction.cpp
#define _CRT_SECURE_NO_WARNINGS
#define PROGRAM_FILE "reduction_complete.cl"
#define ARRAY_SIZE 1048576
#define KERNEL_1 "reduction_vector"
#define KERNEL_2 "reduction_complete"
#include <math.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#ifdef MAC
#include <OpenCL/cl.h>
#else
#include <CL/cl.h>
#endif
/* Find a GPU or CPU associated with the first available platform */
cl_device_id create_device() {
cl_platform_id platform;
cl_device_id dev;
int err;
/* Identify a platform */
err = clGetPlatformIDs(1, &platform, NULL);
if(err < 0) {
perror("Couldn't identify a platform");
exit(1);
}
/* Access a device */
err = clGetDeviceIDs(platform, CL_DEVICE_TYPE_GPU, 1, &dev, NULL);
if(err == CL_DEVICE_NOT_FOUND) {
err = clGetDeviceIDs(platform, CL_DEVICE_TYPE_CPU, 1, &dev, NULL);
}
if(err < 0) {
perror("Couldn't access any devices");
exit(1);
}
return dev;
}
/* Create program from a file and compile it */
cl_program build_program(cl_context ctx, cl_device_id dev, const char* filename) {
cl_program program;
FILE *program_handle;
char *program_buffer, *program_log;
size_t program_size, log_size;
int err;
/* Read program file and place content into buffer */
program_handle = fopen(filename, "r");
if(program_handle == NULL) {
perror("Couldn't find the program file");
exit(1);
}
fseek(program_handle, 0, SEEK_END);
program_size = ftell(program_handle);
rewind(program_handle);
program_buffer = (char*)malloc(program_size + 1);
program_buffer[program_size] = '\0';
fread(program_buffer, sizeof(char), program_size, program_handle);
fclose(program_handle);
/* Create program from file */
program = clCreateProgramWithSource(ctx, 1,
(const char**)&program_buffer, &program_size, &err);
if(err < 0) {
perror("Couldn't create the program");
exit(1);
}
free(program_buffer);
/* Build program */
err = clBuildProgram(program, 0, NULL, NULL, NULL, NULL);
if(err < 0) {
/* Find size of log and print to std output */
clGetProgramBuildInfo(program, dev, CL_PROGRAM_BUILD_LOG,
0, NULL, &log_size);
program_log = (char*) malloc(log_size + 1);
program_log[log_size] = '\0';
clGetProgramBuildInfo(program, dev, CL_PROGRAM_BUILD_LOG,
log_size + 1, program_log, NULL);
printf("%s\n", program_log);
free(program_log);
exit(1);
}
return program;
}
int main() {
/* OpenCL structures */
cl_device_id device;
cl_context context;
cl_program program;
cl_kernel vector_kernel, complete_kernel;
cl_command_queue queue;
cl_event start_event, end_event;
cl_int i, err;
size_t local_size, global_size;
/* Data and buffers */
float data[ARRAY_SIZE];
float sum, actual_sum;
cl_mem data_buffer, sum_buffer;
cl_ulong time_start, time_end, total_time;
/* Initialize data */
for(i=0; i<ARRAY_SIZE; i++) {
data[i] = 1.0f*i;
}
/* Create device and determine local size */
device = create_device();
err = clGetDeviceInfo(device, CL_DEVICE_MAX_WORK_GROUP_SIZE,
sizeof(local_size), &local_size, NULL);
if(err < 0) {
perror("Couldn't obtain device information");
exit(1);
}
/* Create a context */
context = clCreateContext(NULL, 1, &device, NULL, NULL, &err);
if(err < 0) {
perror("Couldn't create a context");
exit(1);
}
/* Build program */
program = build_program(context, device, PROGRAM_FILE);
/* Create data buffer */
data_buffer = clCreateBuffer(context, CL_MEM_READ_WRITE |
CL_MEM_USE_HOST_PTR, ARRAY_SIZE * sizeof(float), data, &err);
sum_buffer = clCreateBuffer(context, CL_MEM_WRITE_ONLY,
sizeof(float), NULL, &err);
if(err < 0) {
perror("Couldn't create a buffer");
exit(1);
};
/* Create a command queue */
queue = clCreateCommandQueue(context, device,
CL_QUEUE_PROFILING_ENABLE, &err);
if(err < 0) {
perror("Couldn't create a command queue");
exit(1);
};
/* Create kernels */
vector_kernel = clCreateKernel(program, KERNEL_1, &err);
complete_kernel = clCreateKernel(program, KERNEL_2, &err);
if(err < 0) {
perror("Couldn't create a kernel");
exit(1);
};
/* Set arguments for vector kernel */
err = clSetKernelArg(vector_kernel, 0, sizeof(cl_mem), &data_buffer);
err |= clSetKernelArg(vector_kernel, 1, local_size * 4 * sizeof(float), NULL);
/* Set arguments for complete kernel */
err = clSetKernelArg(complete_kernel, 0, sizeof(cl_mem), &data_buffer);
err |= clSetKernelArg(complete_kernel, 1, local_size * 4 * sizeof(float), NULL);
err |= clSetKernelArg(complete_kernel, 2, sizeof(cl_mem), &sum_buffer);
if(err < 0) {
perror("Couldn't create a kernel argument");
exit(1);
}
/* Enqueue kernels */
global_size = ARRAY_SIZE/4;
err = clEnqueueNDRangeKernel(queue, vector_kernel, 1, NULL, &global_size,
&local_size, 0, NULL, &start_event);
if(err < 0) {
perror("Couldn't enqueue the kernel");
exit(1);
}
printf("Global size = %zu\n", global_size);
/* Perform successive stages of the reduction */
while(global_size/local_size > local_size) {
global_size = global_size/local_size;
err = clEnqueueNDRangeKernel(queue, vector_kernel, 1, NULL, &global_size,
&local_size, 0, NULL, NULL);
printf("Global size = %zu\n", global_size);
if(err < 0) {
perror("Couldn't enqueue the kernel");
exit(1);
}
}
global_size = global_size/local_size;
err = clEnqueueNDRangeKernel(queue, complete_kernel, 1, NULL, &global_size,
NULL, 0, NULL, &end_event);
printf("Global size = %zu\n", global_size);
/* Finish processing the queue and get profiling information */
clFinish(queue);
clGetEventProfilingInfo(start_event, CL_PROFILING_COMMAND_START,
sizeof(time_start), &time_start, NULL);
clGetEventProfilingInfo(end_event, CL_PROFILING_COMMAND_END,
sizeof(time_end), &time_end, NULL);
total_time = time_end - time_start;
/* Read the result */
err = clEnqueueReadBuffer(queue, sum_buffer, CL_TRUE, 0,
sizeof(float), &sum, 0, NULL, NULL);
if(err < 0) {
perror("Couldn't read the buffer");
exit(1);
}
/* Check result */
actual_sum = 1.0f * (ARRAY_SIZE/2)*(ARRAY_SIZE-1);
if(fabs(sum - actual_sum) > 0.01*fabs(sum))
printf("Check failed.\n");
else
printf("Check passed.\n");
printf("Total time = %lu\n", total_time);
/* Deallocate resources */
clReleaseEvent(start_event);
clReleaseEvent(end_event);
clReleaseMemObject(sum_buffer);
clReleaseMemObject(data_buffer);
clReleaseKernel(vector_kernel);
clReleaseKernel(complete_kernel);
clReleaseCommandQueue(queue);
clReleaseProgram(program);
clReleaseContext(context);
return 0;
}
reduction_complete.cl
__kernel void reduction_vector(__global float4* data,
__local float4* partial_sums) {
int lid = get_local_id(0);
int group_size = get_local_size(0);
partial_sums[lid] = data[get_global_id(0)];
barrier(CLK_LOCAL_MEM_FENCE);
for(int i = group_size/2; i>0; i >>= 1) {
if(lid < i) {
partial_sums[lid] += partial_sums[lid + i];
}
barrier(CLK_LOCAL_MEM_FENCE);
}
if(lid == 0) {
data[get_group_id(0)] = partial_sums[0];
}
}
__kernel void reduction_complete(__global float4* data,
__local float4* partial_sums, __global float* sum) {
int lid = get_local_id(0);
int group_size = get_local_size(0);
partial_sums[lid] = data[get_local_id(0)];
barrier(CLK_LOCAL_MEM_FENCE);
for(int i = group_size/2; i>0; i >>= 1) {
if(lid < i) {
partial_sums[lid] += partial_sums[lid + i];
}
barrier(CLK_LOCAL_MEM_FENCE);
}
if(lid == 0) {
*sum = partial_sums[0].s0 + partial_sums[0].s1 +
partial_sums[0].s2 + partial_sums[0].s3;
}
}
I dont know what causes the stackoverflow…
I don’t see any recursion so my guess is the
float data[ARRAY_SIZE];where#define ARRAY_SIZE 1048576is putting 4MB on the stack which is pretty large. Try changing that to a dynamic allocation.