Concatenation Shortcut

Addition combines two paths by summing matching coordinates.

Concatenation keeps both paths by joining their features:

output = [x, F(x)]

Concatenation preserves both paths by joining features instead of adding them.

If x has 4 channels and F(x) has 6 channels, concatenation produces:

4 + 6 = 10

channels.

Concatenation can preserve more information, but it also increases width. Later layers must learn how to combine the joined features.

Addition says "merge these values." Concatenation says "keep both and decide later."

DL-C15-T04-001Exercise: Concatenated width

One path has 5 channels and another path has 7 channels. How many channels after concatenation?

Your answer

Compute it first, then check your number.

DL-C15-T04-002Exercise: Add or concatenate

Enter 1 if concatenation keeps features by joining them, or 2 if it must sum matching coordinates.

Your answer

Compute it first, then check your number.