layer_prune.py

from models import *
from utils.utils import *
import torch
import numpy as np
from copy import deepcopy
from test import test
from terminaltables import AsciiTable
import time
from utils.utils import *
from utils.prune_utils import *
import argparse


def prune_and_eval(model, prune_shortcuts=[]):
    model_copy = deepcopy(model)
    for idx in prune_shortcuts:
        for i in [idx, idx - 1]:
            bn_module = model_copy.module_list[i][1]

            mask = torch.zeros(bn_module.weight.data.shape[0]).cuda()
            bn_module.weight.data.mul_(mask)

    with torch.no_grad():
        mAP = eval_model(model_copy)[0][2]

    print(f'simply mask the BN Gama of to_be_pruned CBL as zero, now the mAP is {mAP:.4f}')


# %%
def obtain_filters_mask(model, CBL_idx, prune_shortcuts):
    filters_mask = []
    for idx in CBL_idx:
        bn_module = model.module_list[idx][1]
        mask = np.ones(bn_module.weight.data.shape[0], dtype='float32')
        filters_mask.append(mask.copy())
    CBLidx2mask = {idx: mask for idx, mask in zip(CBL_idx, filters_mask)}
    for idx in prune_shortcuts:
        for i in [idx, idx - 1]:
            bn_module = model.module_list[i][1]
            mask = np.zeros(bn_module.weight.data.shape[0], dtype='float32')
            CBLidx2mask[i] = mask.copy()
    return CBLidx2mask


def obtain_avg_forward_time(input, model, repeat=200):
    model.eval()
    start = time.time()
    with torch.no_grad():
        for i in range(repeat):
            output = model(input)
    avg_infer_time = (time.time() - start) / repeat

    return avg_infer_time, output


if __name__ == '__main__':
    parser = argparse.ArgumentParser()
    parser.add_argument('--cfg', type=str, default='cfg/yolov3-hand.cfg', help='cfg file path')
    parser.add_argument('--data', type=str, default='data/oxfordhand.data', help='*.data file path')
    parser.add_argument('--weights', type=str, default='weights/last.pt', help='sparse model weights')
    parser.add_argument('--shortcuts', type=int, default=8, help='how many shortcut layers will be pruned,\
        pruning one shortcut will also prune two CBL,yolov3 has 23 shortcuts')
    parser.add_argument('--img-size', type=int, default=416, help='inference size (pixels)')
    opt = parser.parse_args()
    print(opt)

    img_size = opt.img_size
    device = torch.device("cuda" if torch.cuda.is_available() else "cpu")
    model = Darknet(opt.cfg, (img_size, img_size)).to(device)

    if opt.weights.endswith(".pt"):
        model.load_state_dict(torch.load(opt.weights, map_location=device)['model'])
    else:
        load_darknet_weights(model, opt.weights)
    print('\nloaded weights from ', opt.weights)

    eval_model = lambda model: test(model=model, cfg=opt.cfg, data=opt.data, batch_size=16, imgsz=img_size)
    obtain_num_parameters = lambda model: sum([param.nelement() for param in model.parameters()])

    with torch.no_grad():
        print("\nlet's test the original model first:")
        origin_model_metric = eval_model(model)
    origin_nparameters = obtain_num_parameters(model)

    CBL_idx, Conv_idx, shortcut_idx = parse_module_defs4(model.module_defs)
    print('all shortcut_idx:', [i + 1 for i in shortcut_idx])

    # highest_thre = torch.zeros(len(shortcut_idx))
    # for i, idx in enumerate(shortcut_idx):
    #     highest_thre[i] = model.module_list[idx][1].weight.data.abs().max().clone()
    # _, sorted_index_thre = torch.sort(highest_thre)

    # 这里更改了选层策略，由最大值排序改为均值排序，均值一般表现要稍好，但不是绝对，可以自己切换尝试；前面注释的四行为原策略。
    bn_mean = torch.zeros(len(shortcut_idx))
    for i, idx in enumerate(shortcut_idx):
        bn_mean[i] = model.module_list[idx][1].weight.data.abs().mean().clone()
    _, sorted_index_thre = torch.sort(bn_mean)

    prune_shortcuts = torch.tensor(shortcut_idx)[[sorted_index_thre[:opt.shortcuts]]]
    prune_shortcuts = [int(x) for x in prune_shortcuts]

    index_all = list(range(len(model.module_defs)))
    index_prune = []
    for idx in prune_shortcuts:
        index_prune.extend([idx - 1, idx, idx + 1])
    index_remain = [idx for idx in index_all if idx not in index_prune]

    print('These shortcut layers and corresponding CBL will be pruned :', index_prune)

    prune_and_eval(model, prune_shortcuts)

    CBLidx2mask = obtain_filters_mask(model, CBL_idx, prune_shortcuts)

    pruned_model = prune_model_keep_size(model, CBL_idx, CBL_idx, CBLidx2mask)

    with torch.no_grad():
        mAP = eval_model(pruned_model)[0][2]
    print("after transfering the offset of pruned CBL's activation, map is {}".format(mAP))

    compact_module_defs = deepcopy(model.module_defs)

    for j, module_def in enumerate(compact_module_defs):
        if module_def['type'] == 'route':
            from_layers = [int(s) for s in module_def['layers']]
            if len(from_layers) == 1 and from_layers[0] > 0:
                count = 0
                for i in index_prune:
                    if i <= from_layers[0]:
                        count += 1
                from_layers[0] = from_layers[0] - count
                # from_layers = str(from_layers[0])
                module_def['layers'] = from_layers

            elif len(from_layers) == 2:
                count = 0
                if from_layers[1] > 0:
                    for i in index_prune:
                        if i <= from_layers[1]:
                            count += 1
                    from_layers[1] = from_layers[1] - count
                else:
                    for i in index_prune:
                        if i > j + from_layers[1] and i < j:
                            count += 1
                    from_layers[1] = from_layers[1] + count

                # from_layers = ', '.join([str(s) for s in from_layers])
                module_def['layers'] = from_layers

    compact_module_defs = [compact_module_defs[i] for i in index_remain]
    compact_model = Darknet([model.hyperparams.copy()] + compact_module_defs, (img_size, img_size)).to(device)
    compact_nparameters = obtain_num_parameters(compact_model)

    # init_weights_from_loose_model(compact_model, pruned_model, CBL_idx, Conv_idx, CBLidx2mask)

    random_input = torch.rand((1, 3, img_size, img_size)).to(device)

    pruned_forward_time, pruned_output = obtain_avg_forward_time(random_input, pruned_model)
    compact_forward_time, compact_output = obtain_avg_forward_time(random_input, compact_model)

    # 在测试集上测试剪枝后的模型, 并统计模型的参数数量
    with torch.no_grad():
        compact_model_metric = eval_model(compact_model)

    # 比较剪枝前后参数数量的变化、指标性能的变化
    metric_table = [
        ["Metric", "Before", "After"],
        ["mAP", f'{origin_model_metric[0][2]:.6f}', f'{compact_model_metric[0][2]:.6f}'],
        ["Parameters", f"{origin_nparameters}", f"{compact_nparameters}"],
        ["Inference", f'{pruned_forward_time:.4f}', f'{compact_forward_time:.4f}']
    ]
    print(AsciiTable(metric_table).table)

    # 生成剪枝后的cfg文件并保存模型
    pruned_cfg_name = opt.cfg.replace('/', f'/prune_{opt.shortcuts}_shortcut_')
    # 创建存储目录
    dir_name = pruned_cfg_name.split('/')[0] + '/' + pruned_cfg_name.split('/')[1]
    if not os.path.isdir(dir_name):
        os.makedirs(dir_name)

    # 由于原始的compact_module_defs将anchor从字符串变为了数组，因此这里将anchors重新变为字符串
    file = open(opt.cfg, 'r')
    lines = file.read().split('\n')
    for line in lines:
        if line.split(' = ')[0] == 'anchors':
            anchor = line.split(' = ')[1]
            break
    file.close()
    for item in compact_module_defs:
        if item['type'] == 'shortcut':
            item['from'] = str(item['from'][0])
        elif item['type'] == 'route':
            item['layers'] = ",".join('%s' % i for i in item['layers'])
        elif item['type'] == 'yolo':
            item['mask'] = ",".join('%s' % i for i in item['mask'])
            item['anchors'] = anchor
    pruned_cfg_file = write_cfg(pruned_cfg_name, [model.hyperparams.copy()] + compact_module_defs)
    print(f'Config file has been saved: {pruned_cfg_file}')

    compact_model_name = opt.weights.replace('/', f'/prune_{opt.shortcuts}_shortcut_')
    if compact_model_name.endswith('.pt'):
        compact_model_name = compact_model_name.replace('.pt', '.weights')

    save_weights(compact_model, path=compact_model_name)
    print(f'Compact model has been saved: {compact_model_name}')