CUDA C++: Expected an expression in kernel.cu file

Question

I just started learning a bit of CUDA, and I encountered this error in the following line, at a <<< >>> expression

#include "kernels.h"
#include "helpers.h"
#include <iostream>
#include <cmath>
#include <cuda_runtime.h>
#include <device_launch_parameters.h>
__global__
void blur(unsigned char* input_image, unsigned char* output_image, int width, int height) {

    const unsigned int offset = blockIdx.x*blockDim.x + threadIdx.x;
    int x = offset % width;
    int y = (offset - x) / width;
    int fsize = 5; // Filter size
    if (offset < width*height) {

        float output_red = 0;
        float output_green = 0;
        float output_blue = 0;
        int hits = 0;
        for (int ox = -fsize; ox < fsize + 1; ++ox) {
            for (int oy = -fsize; oy < fsize + 1; ++oy) {
                if ((x + ox) > -1 && (x + ox) < width && (y + oy) > -1 && (y + oy) < height) {
                    const int currentoffset = (offset + ox + oy * width) * 3;
                    output_red += input_image[currentoffset];
                    output_green += input_image[currentoffset + 1];
                    output_blue += input_image[currentoffset + 2];
                    hits++;
                }
            }
        }
        output_image[offset * 3] = output_red / hits;
        output_image[offset * 3 + 1] = output_green / hits;
        output_image[offset * 3 + 2] = output_blue / hits;
    }
}


void filter(unsigned char* input_image, unsigned char* output_image, int width, int height) {

    unsigned char* dev_input;
    unsigned char* dev_output;
    getError(cudaMalloc((void**)&dev_input, width*height * 3 * sizeof(unsigned char)));
    getError(cudaMemcpy(dev_input, input_image, width*height * 3 * sizeof(unsigned char), cudaMemcpyHostToDevice));

    getError(cudaMalloc((void**)&dev_output, width*height * 3 * sizeof(unsigned char)));

    dim3 blockDims(512, 1, 1);
    dim3 gridDims((unsigned int)ceil((double)(width*height * 3 / blockDims.x)), 1, 1);

    blur <<< gridDims, blockDims >>>(dev_input, dev_output, width, height);


    getError(cudaMemcpy(output_image, dev_output, width*height * 3 * sizeof(unsigned char), cudaMemcpyDeviceToHost));

    getError(cudaFree(dev_input));
    getError(cudaFree(dev_output));
}

In the

blur <<< gridDims, blockDims >>>(dev_input, dev_output, width, height);

line, at the third < in it, I encounter the error from the title, and because of it I can't compile the code (Other people said that it is an Intellisense error, but for other people the program compilled, while mine doesn't).

I also receive this error when I try to compile

Severity    Code    Description Project File    Line    Suppression State
Error   MSB3721 The command ""C:\Program Files\NVIDIA GPU Computing Toolkit\CUDA\v9.1\bin\nvcc.exe" -gencode=arch=compute_30,code=\"sm_30,compute_30\" --use-local-env --cl-version 2017 -ccbin "C:\Program Files (x86)\Microsoft Visual Studio\2017\Enterprise\VC\Tools\MSVC\14.12.25827\bin\HostX86\x64" -x cu  -I"C:\Program Files\NVIDIA GPU Computing Toolkit\CUDA\v9.1\include" -I"C:\Program Files\NVIDIA GPU Computing Toolkit\CUDA\v9.1\include"  -G   --keep-dir x64\Debug -maxrregcount=0  --machine 64 --compile -cudart static  -g   -DWIN32 -DWIN64 -D_DEBUG -D_CONSOLE -D_MBCS -Xcompiler "/EHsc /W3 /nologo /Od /FS /Zi /RTC1 /MDd " -o x64\Debug\kernel.cu.obj "C:\Users\Artyomska\Documents\Visual Studio 2017\Projects\ScreenFilter\ScreenFilter\kernel.cu"" exited with code 1. ScreenFilter    C:\Program Files (x86)\Microsoft Visual Studio\2017\Enterprise\Common7\IDE\VC\VCTargets\BuildCustomizations\CUDA 9.1.targets    707 

I am trying to run the program on Windows 10, Visual Studio 2017 (the latest version, with toolkit for 15.4 support installed so I don't receive incompatible version error). I have tried reinstalling CUDA 9.1.85, VS2017 and create a new project. I added paths in dependencies and libraries to the NVIDIA Toolkit, and that code is present in a .cu file.

The problem is that even if I create a new project, without changing anything and letting kernel.cu with how the default settings populate it, it still has the expression error at a <<< >>> line.

What should I do to resolve it? Thank you.

Answer 1

I found the problem. The newest version of VS2017 doesn't support the newest version of CUDA, so the solution was to do what it's told in here . Now everything works

Answer 2

I had the same compile time error. Right click on the file in visual studio->Properties->Configuration Properties->Item Type (Set this as CUDA C/C++)

Answer 3

Since I have experienced this error MANY times, I just wanted to add that if you see this error shown with any other errors make sure that you take care of other errors first. It is very likely that this error is not the actual cause of your failed compilation though it may show up as the first error on the list of errors.