block2.py

""" 
Information about architecture config:
Tuple is structured by and signifies a convolutional block (filters, kernel_size, stride) 
Every convolutional layer is a same convolution. 
List is structured by "B" indicating a residual block followed by the number of repeats. 
"S" is for a scale prediction block and computing the yolo loss
"U" is for upsampling the feature map
"""
config = [
    (32, 3, 1),
    (64, 3, 2),
    ["B", 1],
    (128, 3, 2),
    ["B", 2],
    (256, 3, 2),
    ["B", 8],
    # first route from the end of the previous block
    (512, 3, 2),
    ["B", 8], 
    # second route from the end of the previous block
    (1024, 3, 2),
    ["B", 4],
    # until here is YOLO-53
    (512, 1, 1),
    (1024, 3, 1),
    "S",
    (256, 1, 1),
    "U",
    (256, 1, 1),
    (512, 3, 1),
    "S",
    (128, 1, 1),
    "U",
    (128, 1, 1),
    (256, 3, 1),
    "S",
]