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Hello every one, I am new with cuda
I have two arrays:

double* A = new double[]{1,2,3,4,5};

double* B = new double[]{2,2,2,3,3,3,4,4,4};

I want to find the index of the value of each element in A that is equal to each element in B, which in this case is:

int* index = {1,1,1,2,2,2,3,3,3};

but I get this

<pre>int* index = {0,0,0,0,0,0,0,0,0};

here is my code:
#include "cuda_runtime.h"
#include "device_functions.h" 
#include "device_launch_parameters.h"
#include <iostream>
#include <stdio.h>
#include <stdlib.h>
#include <cstdlib>
#include <cuda.h>

#include "kernel.h"

using namespace std;

__global__ void add(int n, float* x, float* y)

	int index  = blockIdx.x * blockDim.x + threadIdx.x;
	int stride = blockDim.x * gridDim.x;
	for (int i = index; i < n; i+=stride)
		y[i] = x[i] + y[i];

__global__ void findIndex(int n, double* x, double* y, double* v)
	int index = threadIdx.x;

	for (int i = 0; i < n; i++)
		if (y[i] = x[index])
			v[index] = i;

int main() {

	double* A = new double[5]{1,2,3,4,5};
	double* B = new double[9] {2,2,2,3,3,3,4,4,4};
	double* C = new double[9];

	double* AA;
	double* BB;
	double* CC;

	cudaMallocManaged(&AA, 5 * sizeof(double));
	cudaMallocManaged(&BB, 9 * sizeof(double));
	cudaMallocManaged(&CC, 9 * sizeof(double));

	dim3 grid(9);
	findIndex << <grid, 1 >> > (9, BB,AA, CC);

	for (int i = 0; i < 9; i++)
		printf("{%d}", CC[i]);


	int m = 0;

	return 0;


What I have tried:

I have tried everything but I do not get the results I want
Updated 14-Jun-21 1:10am

1 solution

I am not sure about the code I would write:
findIndex(9, BB,AA, CC);

else you must store the result and set some useful return value.

You must compare each scalar of the array with the searched element value.

I recommand that you work with structs to be clearer in your code.
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