CODEWITHSUNDEEP
c++cudaprintfgpu
einpoklum
einpoklum

Reputation: 131950

Why do I need to include <stdio.h> to use CUDA's printf()?

I want to printf() something in my CUDA kernel. The Programming Guide suggests I do that like so:

#include <stdio.h>

__global__ void helloCUDA(float f)
{
    printf("Hello thread %d, f=%f\n", threadIdx.x, f);
}

But this is simply including the standard C library's stdio.h. Why would that be necessary? CUDA's printf() doesn't have the same behavior of stdio's printf(); and I certainly don't need most of everything else that's in there.

Upvotes: 3

Views: 1854

Answers (1)

talonmies
talonmies

Reputation: 72339

It's an implementation detail you don't need to know about which stems from limitations in the CUDA syntax (basically it is illegal to define different __device__ and __host__ versions of the same function).

The standard library prototype is used as a proxy in device code during compilation, and when compiling for a supported architecture, some sneaky template overloading is used to insert the device implementation into the device code.

Upvotes: 6

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