5. Specific operations

5.1 Convolutions

The convolution principle is illustrated in figure 13 . A 2*2 filter is used with an activation map of size 3*3. Starting from the top left corner of the activation map, the filter is applied to the activation map and generates a value placed at the top corner of the result map. The filter is then shifted one position to the right for the next value on the result map. When the filter reaches the last placement, we start again from the next line. With a 2*2 filter on a 3*3 activation card, we obtain a 2*2 result activation card. This example uses a filter offset step of 1. A step greater than 1 can be used.