How does 'route' layer work in yolov2?

[wsyzzz]

Hi everyone, does anyone know how 'route' layer work in yolov2? I google it and only find that "the route layer is to bring finer grained features in from earlier in the network". So how it 'bring finer grained features in'?

E.g. I provide a case to explain. I use ./darknet detector test cfg/coco.data cfg/yolo.cfg yolo.weights data/dog.jpg

layer        |          filters         |           size          |            input                   |             output           |
0 conv                    32                     3×3  /  1                   416×416×3                ->           416×416×32
……
16  conv                 512                     3×3  /  1                   26×26×256                ->           26×26×512
……
24  conv                1024                     3×3  /  1                   13×13×1024               ->           13×13×1024
25  route                16
26  conv                 64                      1×1  /  1                   26×26×512                ->           26×26×64
27  reorg                                             /  2                   26×26×64                 ->           13×13×256
28  route              27  24
29  conv                1024                     3×3  /  1                   13×13×1280               ->           13×13×1024
……

And in 'yolo.cfg', I found that

[route]                            
layers=-9
……
[route]  
layers=-1,-3 

So It's clear that the 25th route layer uses 16th layer for 'layers=-9' in .cfg file, the 28th route layer uses 27th and 24th layer for 'layers=-1, -3' in .cfg file.

Here is my question. How the route layer how the 25th route layer uses 13×13×1024 input from the 24th layer and 26×26×512 input from the 16th layer to obtain 26×26×512 output(according to the 26th input)?

I am looking for any advice. Thanks for your response!

[wsyzzz]

This problem is solved here.
#487

[khanh101]

Can you leave the answer or link below for others?

[AlexeyAB]

@khanh1412

Links:

• explanation on cfg file parameters AlexeyAB/darknet#279 (comment)
• How does 'route' layer work in yolov2? AlexeyAB/darknet#487 (comment)