stupid_simple_conv_kernel.jl

function gauss(A, i, j, ui, uj)
    nw, n, ne = 1.0f0/9.0f0, 1.0f0/9.0f0, 1.0f0/9.0f0
    w,  c, e  = 1.0f0/9.0f0, 1.0f0/9.0f0, 1.0f0/9.0f0
    sw, s, se = 1.0f0/9.0f0, 1.0f0/9.0f0, 1.0f0/9.0f0

    top , bottom = j - 1, uj - j
    left, right  = i - 1, ui - i

    nw *= clamp(top * left, 0, 1)
    n  *= clamp(top, 0, 1)
    ne *= clamp(top * right, 0, 1)
    w  *= clamp(left, 0, 1)
    e  *= clamp(right, 0, 1)
    sw *= clamp(bottom * left, 0, 1)
    s  *= clamp(bottom, 0, 1)
    se *= clamp(bottom * right, 0, 1)
    
    # Clamp local neighborhood
    x1, x2 = max(i-1, 1), min(i+1, ui)
    y1, y2 = max(j-1, 1), min(j+1, uj)

    # Sum over local neighborhood
    lapl  = A[x1, y1] * nw + A[i, y1] * n + A[x2, y1] * ne
    lapl += A[x1, j]  * w  + A[i,j]   * c + A[x2, j]  * e
    lapl += A[x1, y2] * sw + A[i, y2] * s + A[x2, y2] * se
    
    return Float32(lapl)
end

function gauss_conv!(A, w, h)
    
    # Get block index.
    i = (blockIdx().x-UInt32(1)) * blockDim().x + threadIdx().x
    j = (blockIdx().y-UInt32(1)) * blockDim().y + threadIdx().y
    
    A[i,j] = gauss(A, i, j, w, h)

    nothing
end