CUDA and C++ function problems ( Visual Studio 2013)

Question

I am trying to call a cuda function that is defined in a cu file from a cpp file in Visual Studio but I keep receiving the following error.

TomColourCorrectionMain.obj : error LNK2019: unresolved external symbol "public: void __cdecl hwk::TomColourCorrection::brightness(int,int)" (?brightness@TomColourCorrection@hwk@@QEAAXHH@Z) referenced in function "public: virtual void __cdecl hwk::TomColourCorrection::processCore(class std::shared_ptr)" (?processCore@TomColourCorrection@hwk@@UEAAXV?$shared_ptr@VIImageProcessingContext@hwk@@@std@@@Z)

Now from reading other questions similar to this, I understand its to do with how the function is defined and that there is something wrong there but I can't see it from when I have defined in the header and cuda file.

This is the code I have (I am a novice at CUDA but I can compile CUDA fine and the code runs when I don't call this function in C++):

header file

#pragma once

#include "ImageProcessorWithProperties.h"
#include <iostream>
#include <cuda_runtime.h>
#include    <cuda.h>

class TomColourCorrection : public ImageProcessorWithProperties, public      PropertyConsumer<TomColourCorrection>{
public: TomColourCorrection(PropNodePtr n, std::function<void()> requestReprocess);

    virtual void processCore(IImageProcessingContextPtr context);

static void DeclareSettings(hwk::PropNodePtr n);

virtual ~TomColourCorrection();

void brightness(int iw, int ih); (function I am talking about)
};
 }

cpp file with function call //its just segments of the important code as the rest of it isn't necessary for the actual function itself

 #include "stdafx.h"
 #include "TomColourCorrection.h"

 #include <opencv2/imgproc/imgproc.hpp>
 #include <cv.h>
 #include <highgui.h>
 #include <opencv2/core/core.hpp>
 #include <opencv2/highgui/highgui.hpp>
 #include <iostream>

 #include <cuda_runtime.h>
 #include   <cuda.h>

 namespace hwk{ 

    TomColourCorrection::TomColourCorrection(PropNodePtr n, std::function<void()> requestReprocess) :
ImageProcessorWithProperties("sandbox", n, requestReprocess),
PropertyConsumer<TomColourCorrection>(n)
{

 }

void TomColourCorrection::processCore(IImageProcessingContextPtr context){



 brightness(16, 16); (just generic numbers at the moment as I am trying to resolve this issue etc)
    }
  }

CUDA File and function definition

#include "TomColourCorrection.h"
#include "device_launch_parameters.h"

__global__ void brightness_kernel(int iw, int ih)
{
// Calculate our pixel's location
int x = (blockIdx.x * blockDim.x) + threadIdx.x;
int y = (blockIdx.y * blockDim.y) + threadIdx.y;

// Variables to store the sum
int count = 0;
float sum = 0.0;

// Do the blur operation by summing the surround pixels
/*  for (int j = -(bh / 2); j <= (bh / 2); j++)
{
    for (int i = -(bw / 2); i <= (bw / 2); i++)
    {
        // Verify that this offset is within the image boundaries
        if ((x + i) < iw && (x + i) >= 0 && (y + j) < ih && (y + j) >= 0)
        {
            sum += (float)source[((y + j) * iw) + (x + i)];
            count++;
        }
    }
}*/

// Average the sum
sum /= (float)count;
//  dest[(y * iw) + x] = (unsigned char)sum;
}



void brightness(int iw, int ih) //, unsigned char *source, unsigned char *dest)
{
// allocate memory for the bitmap in GPU memory
unsigned char *dev_source, *dev_dest;
//  cudaHostGetDevicePointer(&dev_source, source, 0);
//  cudaHostGetDevicePointer(&dev_dest, dest, 0);

// Run the boxfilter kernel
dim3 blocks(iw / 16, ih / 16);
dim3 threads(16, 16);

// Execute the kernel
brightness_kernel << <blocks, threads >> >(iw, ih);
cudaThreadSynchronize();
}

Answer 1

Modify the TomColourCorrection.h like this:

#pragma once

#include "ImageProcessorWithProperties.h"
#include <iostream>
#include <cuda_runtime.h>
#include    <cuda.h>

void brightness_wrapper(int, int);
class TomColourCorrection : public ImageProcessorWithProperties, public      PropertyConsumer<TomColourCorrection>{

  public: 
    TomColourCorrection(PropNodePtr n, std::function<void()> requestReprocess);

    virtual void processCore(IImageProcessingContextPtr context);

    static void DeclareSettings(hwk::PropNodePtr n);

    virtual ~TomColourCorrection();

    void brightness(int iw, int ih); 
};

Modify your cpp file like this:

 #include "stdafx.h"
 #include "TomColourCorrection.h"

 #include <opencv2/imgproc/imgproc.hpp>
 #include <cv.h>
 #include <highgui.h>
 #include <opencv2/core/core.hpp>
 #include <opencv2/highgui/highgui.hpp>
 #include <iostream>

 #include <cuda_runtime.h>
 #include   <cuda.h>

 namespace hwk{ 

    void TomColourCorrection::brightness(int iw, int ih){
      brightness_wrapper(iw, ih);}

    TomColourCorrection::TomColourCorrection(PropNodePtr n, std::function<void()> requestReprocess) : ImageProcessorWithProperties("sandbox", n, requestReprocess),  PropertyConsumer<TomColourCorrection>(n)
      {

      }

    void TomColourCorrection::processCore(IImageProcessingContextPtr context){
        brightness(16, 16); 
    }
  }

And in your cuda file change this:

void brightness(int iw, int ih) //, unsigned char *source, unsigned char *dest)

to this:

void brightness_wrapper(int iw, int ih) //, unsigned char *source, unsigned char *dest)

This is mainly just spelling out the details of Ryck's answer.