Is this a typo in Chatper: Convolution

ishan · September 17, 2020, 2:23pm

Hi,
Is this a typo in the convolution. It seems like the signs are reversed. I have attached images to show the kernel and the sample matrix. Should the equation be -a1-a2-a3+a7+a8+a9? Unless I am betting something backwards.
Thanks

Here is the link to the chapter.

github.com

fastai/fastbook/blob/master/13_convolutions.ipynb

{
 "cells": [
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "#hide\n",
    "!pip install -Uqq fastbook\n",
    "import fastbook\n",
    "fastbook.setup_book()"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [

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Sturzgefahr · October 8, 2020, 4:48am

I think you’re right. I’m reading through the book right now and I noticed the exact same thing.