Hi,
I’m trying to use clEnqueueBufferRect to copy data out of a buffer with some stride. It works just fine when the buffer is filled with int
's, but if I change it to float
or double
it does not work anymore. By that I mean that it doesn’t seem to copy anything, the receiving buffer remains unchanged with no values written into it. Here is a small compilable test code that demonstrates the issue (here I use the C++ API but the same happens with the C API):
#include <iostream>
#define __CL_ENABLE_EXCEPTIONS
#include <CL/cl.hpp>
int main(int argc, char** argv) {
// Set up OpenCL environment
cl::Context context;
cl::Device device;
cl::CommandQueue queue;
try {
std::vector<cl::Platform> all_platforms;
cl::Platform::get(&all_platforms);
cl::Platform tauschcl_platform = all_platforms[0];
std::vector<cl::Device> all_devices;
tauschcl_platform.getDevices(CL_DEVICE_TYPE_ALL, &all_devices);
device = all_devices[0];
std::cout << "Using OpenCL device " << device.getInfo<CL_DEVICE_NAME>() << std::endl;
// Create context and queue
context = cl::Context({device});
queue = cl::CommandQueue(context,device);
} catch(cl::Error &error) {
std::cout << "OpenCL exception caught: " << error.what() << " (" << error.err() << ")" << std::endl;
return 1;
}
/*********************/
// Thus works with int
// but not float nor double
typedef int buf_t;
/*********************/
// Start buffer, length 10, filled with integers from 1 to 10
buf_t *buf1 = new buf_t[10]{};
for(int i = 0; i < 10; ++i)
buf1[i] = i+1;
// create an opencl buffer with same content
cl::Buffer clbuf(queue, &buf1[0], &buf1[10], true);
// receiving buffer of length 5, initialised to zero
buf_t *buf2 = new buf_t[5]{};
// buffer/host offsets are both (0,0,0)
cl::size_t<3> buffer_offset;
buffer_offset[0] = 0; buffer_offset[1] = 0; buffer_offset[2] = 0;
cl::size_t<3> host_offset;
host_offset[0] = 0; host_offset[1] = 0; host_offset[2] = 0;
// We copy 5 values (with stride of 2)
cl::size_t<3> region;
region[0] = 1; region[1] = 5; region[2] = 1;
try {
queue.enqueueReadBufferRect(clbuf,
CL_TRUE,
buffer_offset,
host_offset,
region,
2*sizeof(buf_t), // buffer stride of 2
0,
1*sizeof(buf_t), // host stride of 1
0,
buf2);
} catch(cl::Error &error) {
std::cout << "OpenCL exception caught: " << error.what() << " (" << error.err() << ")" << std::endl;
return 1;
}
// print result
for(int i = 0; i < 5; ++i)
std::cout << "#" << i << " = " << buf2[i] << " --> should be " << 2*i+1 << std::endl;
return 0;
}
The above code works just fine as is (with int
), but it can be observed to fail when changing int
in line 38 (the typedef
) to float
or double
, suddenly nothing seems to be copied. But why?