Question

While compiling this hello world sample in Ubuntu 10.10

This is from CUDA by Example, chapter 3 (No compile instructions provided >:@)

#include <iostream>

__global__ void kernel (void){


}

int main(void){

    kernel <<<1,1>>>();
        printf("Hellow World!\n");
    return 0;

}

I got this:

$ nvcc -lcudart hello.cu hello.cu(11): error: identifier “printf” is
undefined

1 error detected in the compilation of
“/tmp/tmpxft_00007812_00000000-4_hello.cpp1.ii”.

Why? How should this code be compiled?

Answer 1

You need to include stdio.h or cstdionot iostream (which is for std::cout stuff) for printf (see man 3 printf). I found the source code for the book here.

chapter03/hello_world.cu is actually:

/*
 * Copyright 1993-2010 NVIDIA Corporation.  All rights reserved.
 *
 * NVIDIA Corporation and its licensors retain all intellectual property and 
 * proprietary rights in and to this software and related documentation. 
 * Any use, reproduction, disclosure, or distribution of this software 
 * and related documentation without an express license agreement from
 * NVIDIA Corporation is strictly prohibited.
 *
 * Please refer to the applicable NVIDIA end user license agreement (EULA) 
 * associated with this source code for terms and conditions that govern 
 * your use of this NVIDIA software.
 * 
 */


#include "../common/book.h"

int main( void ) {
    printf( "Hello, World!\n" );
    return 0;
}

Where ../common/book.h includes stdio.h.

The README.txt file details how to compile the examples:

The vast majority of these code examples can be compiled quite easily by using 
NVIDIA's CUDA compiler driver, nvcc. To compile a typical example, say 
"example.cu," you will simply need to execute:

> nvcc example.cu