parse_network_cfg_custom函式中，讀取配置檔案是先把各個section讀取出來，然後再解析。
yolov3.cfg裡面只有幾個不同的section，分別是[net]、[convolutional]、[shortcut]、[yolo]、[route]、[upsample]，下面分別探究。

NET（全域性）

參考 YOLO配置檔案理解

convolutional

引數：

相應程式碼段：

    int n = option_find_int(options, "filters",1);
    int size = option_find_int(options, "size",1);
    int stride = option_find_int(options, "stride",1);
    int pad = option_find_int_quiet(options, "pad",0);
    int padding = option_find_int_quiet(options, "padding",0);
    if(pad) padding = size/2;
    char *activation_s = option_find_str(options, "activation", "logistic");
    int batch_normalize = option_find_int_quiet(options, "batch_normalize", 0);
    int binary = option_find_int_quiet(options, "binary", 0);
    int xnor = option_find_int_quiet(options, "xnor", 0);
    int use_bin_output = option_find_int_quiet(options, "bin_output", 0);

shortcut

引數：

相應程式碼段：

layer parse_shortcut(list *options, size_params params, network net)
{
    char *l = option_find(options, "from");
    int index = atoi(l);
    if(index < 0) index = params.index + index;

    int batch = params.batch;
    layer from = net.layers[index];

    layer s = make_shortcut_layer(batch, index, params.w, params.h, params.c, from.out_w, from.out_h, from.out_c);

    char *activation_s = option_find_str(options, "activation", "linear");
    ACTIVATION activation = get_activation(activation_s);
    s.activation = activation;
    return s;
}

yolo

引數：

相應程式碼段：

layer parse_yolo(list *options, size_params params)
{
    int classes = option_find_int(options, "classes", 20);
    int total = option_find_int(options, "num", 1);
    int num = total;

    char *a = option_find_str(options, "mask", 0);
    int *mask = parse_yolo_mask(a, &num);
    int max_boxes = option_find_int_quiet(options, "max", 90);
    layer l = make_yolo_layer(params.batch, params.w, params.h, num, total, mask, classes, max_boxes);
    if (l.outputs != params.inputs) {
        printf("Error: l.outputs == params.inputs \n");
        printf("filters= in the [convolutional]-layer doesn't correspond to classes= or mask= in [yolo]-layer \n");
        exit(EXIT_FAILURE);
    }
    //assert(l.outputs == params.inputs);

    //l.max_boxes = option_find_int_quiet(options, "max", 90);
    l.jitter = option_find_float(options, "jitter", .2);
    l.focal_loss = option_find_int_quiet(options, "focal_loss", 0);

    l.ignore_thresh = option_find_float(options, "ignore_thresh", .5);
    l.truth_thresh = option_find_float(options, "truth_thresh", 1);
    l.random = option_find_int_quiet(options, "random", 0);

    char *map_file = option_find_str(options, "map", 0);
    if (map_file) l.map = read_map(map_file);

    a = option_find_str(options, "anchors", 0);
    if (a) {
        int len = strlen(a);
        int n = 1;
        int i;
        for (i = 0; i < len; ++i) {
            if (a[i] == ',') ++n;
        }
        for (i = 0; i < n && i < total*2; ++i) {
            float bias = atof(a);
            l.biases[i] = bias;
            a = strchr(a, ',') + 1;
        }
    }
    return l;
}

route

route layer只有一個引數，layers，指定一個輸入的layer。

route_layer parse_route(list *options, size_params params, network net)
{
    char *l = option_find(options, "layers");
    int len = strlen(l);
    if(!l) error("Route Layer must specify input layers");
    int n = 1;
    int i;
    for(i = 0; i < len; ++i){
        if (l[i] == ',') ++n;
    }

    int *layers = calloc(n, sizeof(int));
    int *sizes = calloc(n, sizeof(int));
    for(i = 0; i < n; ++i){
        int index = atoi(l);
        l = strchr(l, ',')+1;
        if(index < 0) index = params.index + index;
        layers[i] = index;
        sizes[i] = net.layers[index].outputs;
    }
    int batch = params.batch;

    route_layer layer = make_route_layer(batch, n, layers, sizes);

    convolutional_layer first = net.layers[layers[0]];
    layer.out_w = first.out_w;
    layer.out_h = first.out_h;
    layer.out_c = first.out_c;
    for(i = 1; i < n; ++i){
        int index = layers[i];
        convolutional_layer next = net.layers[index];
        if(next.out_w == first.out_w && next.out_h == first.out_h){
            layer.out_c += next.out_c;
        }else{
            layer.out_h = layer.out_w = layer.out_c = 0;
        }
    }

    return layer;
}

upsample

顧名思義，這個layer是用來做上取樣的，只有stride和scale兩個引數，程式碼如下

layer parse_upsample(list *options, size_params params, network net)
{

    int stride = option_find_int(options, "stride", 2);
    layer l = make_upsample_layer(params.batch, params.w, params.h, params.c, stride);
    l.scale = option_find_float_quiet(options, "scale", 1);
    return l;
}