hello world example

Discussion created by florian100 on Jan 28, 2010
Latest reply on Feb 12, 2010 by bridgman
question to the hello world example


I just started learning opencl and I tryed to run the hello world example provided by Benedict Gaster


sadly I didn't get it to run, I get the following error:


PC:~/opencl$ gcc -o hello_world -Ipath-OpenCL-include -Lpath-OpenCL-libdir lesson1.cpp -lOpenCL
lesson1.cpp: In function ‘int main()’:
lesson1.cpp:31: error: no matching function for call to ‘cl::Platform::get(std::vector >*)’
cl.hpp:1419: note: candidates are: static cl_int cl::Platform::get(cl::vector*)
lesson1.cpp:36: error: no matching function for call to ‘cl::Platform::getInfo(int, std::string*)’
cl.hpp:1334: note: candidates are: cl_int cl::Platform::getInfo(cl_platform_info, cl::STRING_CLASS*) const

I am using ubuntu

PC:~/opencl$ cat /proc/version
Linux version 2.6.31-14-generic (buildd@crested) (gcc version 4.4.1 (Ubuntu 4.4.1-4ubuntu8) ) #48-Ubuntu SMP Fri Oct 16 14:05:01 UTC 2009


I attached my program

// lesson1.cpp #include <utility> #define __NO_STD_VECTOR // Use cl::vector and cl::string and #define __NO_STD_STRING // not STL versions, more on this later #include "cl.hpp" #include <cstdio> #include <cstdlib> #include <fstream> #include <iostream> #include <string> #include <iterator> #include <vector> const std::string hw("Hello World\n"); inline void checkErr(cl_int err, const char * name) { if (err != CL_SUCCESS) { std::cerr << "ERROR: " << name << " (" << err << ")" << std::endl; exit(EXIT_FAILURE); } } int main(void) { cl_int err; std::vector< cl::Platform > platformList; cl::Platform::get(&platformList); checkErr(platformList.size()!=0 ? CL_SUCCESS : -1, "cl::Platform::get"); std::cerr << "Platform number is: " << platformList.size() << std::endl; std::string platformVendor; platformList[0].getInfo(CL_PLATFORM_VENDOR, &platformVendor); std::cerr << "Platform is by: " << platformVendor << "\n"; cl_context_properties cprops[3] = {CL_CONTEXT_PLATFORM, (cl_context_properties)(platformList[0])(), 0}; cl::Context context( CL_DEVICE_TYPE_CPU, cprops, NULL, NULL, &err); checkErr(err, "Conext::Context()"); char * outH = new char[hw.length()+1]; cl::Buffer outCL( context, CL_MEM_WRITE_ONLY | CL_MEM_USE_HOST_PTR, hw.length()+1, outH, &err); checkErr(err, "Buffer::Buffer()"); cl::vector<cl::Device> devices; devices = context.getInfo<CL_CONTEXT_DEVICES>(); checkErr( devices.size() > 0 ? CL_SUCCESS : -1, "devices.size() > 0"); std::ifstream file("lesson1_kernels.cl"); checkErr(file.is_open() ? CL_SUCCESS:-1, "lesson1_kernel.cl"); std::string prog( std::istreambuf_iterator<char>(file), (std::istreambuf_iterator<char>())); cl::Program::Sources source( 1, std::make_pair(prog.c_str(), prog.length()+1)); cl::Program program(context, source); err = program.build(devices,""); checkErr(file.is_open() ? CL_SUCCESS : -1, "Program::build()"); cl::Kernel kernel(program, "hello", &err); checkErr(err, "Kernel::Kernel()"); err = kernel.setArg(0, outCL); checkErr(err, "Kernel::setArg()"); cl::CommandQueue queue(context, devices[0], 0, &err); checkErr(err, "CommandQueue::CommandQueue()"); cl::Event event; err = queue.enqueueNDRangeKernel( kernel, cl::NullRange, cl::NDRange(hw.length()+1), cl::NDRange(1, 1), NULL, &event); checkErr(err, "ComamndQueue::enqueueNDRangeKernel()"); event.wait(); err = queue.enqueueReadBuffer( outCL, CL_TRUE, 0, hw.length()+1, outH); checkErr(err, "ComamndQueue::enqueueReadBuffer()"); std::cout << outH; return EXIT_SUCCESS; } // lesson1_kernal.cl #pragma OPENCL EXTENSION cl_khr_byte_addressable_store : enable __constant char hw[] = "Hello World\n"; __kernel void hello(__global char * out) { size_t tid = get_global_id(0); out[tid] = hw[tid]; }