Typo in the addition kernel in muladd.cu

[ferrarioa5]

There is a typo in the add_kernel routine in the CUDA file muladd.cu. I assumed that this kernel should compute the sum of two tensors, but it acually computes the multiplication:

__global__ void add_kernel(int numel, const float* a, const float* b, float* result) {
  int idx = blockIdx.x * blockDim.x + threadIdx.x;
  if (idx < numel) result[idx] = a[idx] * b[idx];
}

This bug can be tested by running the following python script:

import extension_cpp as ext
import torch

device = 'cuda'
n=100
a = torch.rand(n).to(device)
b = torch.rand(n).to(device)
add2 = torch.zeros(n).to(device)

add1=a+b
ext.ops.myadd_out(a,b,add2)
print(torch.equal(add1,add2))

The CPU implementation gives the correct result (with device="cpu" in the code above).

[cyk2018]

yes, I also hink this is an error.