def train()

in FasterRCNNDetection/train.py [0:0]


def train(**kwargs):
    """
    The main entry point for training; trains a FasterRCNN-based detector.
    """

    opt._parse(kwargs)

    # Loading class names from checkpoint, if available
    # We need to load the checkpoint here 
    if opt.load_path:
        old_state = torch.load(opt.load_path)
        class_names = old_state['class_names']
        best_map = old_state['best_map']
    else:
        class_names = []
        best_map = 0
        old_state = None

    print('load data')
    dataset = Dataset(opt, class_names)
    dataloader = data_.DataLoader(dataset, \
                                  batch_size=1, \
                                  shuffle=True, \
                                  # pin_memory=True,
                                  num_workers=opt.num_workers)

    testset = TestDataset(opt, dataset.get_class_names())
    test_dataloader = data_.DataLoader(testset, \
                                       batch_size=1, \
                                       num_workers=opt.test_num_workers,
                                       shuffle=False, \
                                       pin_memory=True
                                       )

    faster_rcnn = FasterRCNNVGG16(n_fg_class=dataset.get_class_count())
    print('Model construct completed')
    trainer = FasterRCNNTrainer(faster_rcnn, n_fg_class=dataset.get_class_count())


    if opt.use_cuda:

        trainer = trainer.cuda()

    if opt.load_path:

        trainer.load(old_state)
        print_log('load pretrained model from %s' % opt.load_path)

    if opt.validate_only:

        num_eval_images = len(testset)
        eval_result = eval(test_dataloader, faster_rcnn, trainer, testset, global_step, test_num=num_eval_images)
        print_log('Evaluation finished, obtained {} using {} out of {} images'.
                format(eval_result, num_eval_images, len(testset)))
        return
    
    if old_state and 'epoch' in old_state.keys():

        starting_epoch = old_state['epoch'] + 1
        print_log('Model was trained until epoch {}, continuing with epoch {}'.format(old_state['epoch'], starting_epoch))

    else:

        starting_epoch = 0
    
    lr_ = opt.lr
    global_step = 0

    for epoch in range(starting_epoch, opt.num_epochs):

        writer.add_scalar('epoch', epoch, global_step)
        lr_ = opt.lr * (opt.lr_decay ** np.sum(epoch >= np.array(opt.lr_schedule)))
        trainer.faster_rcnn.set_lr(lr_)

        print_log('Starting epoch {} with learning rate {}'.format(epoch, lr_))
        trainer.reset_meters()
        for ii, (img, bbox_, label_, scale) in tqdm(enumerate(dataloader), total=len(dataset)):
            global_step = global_step + 1
            scale = at.scalar(scale).item()
            if opt.use_cuda: 
                img = img.cuda().float()
                label = label_.float().cuda()

                if len(bbox_[0]) > 0:
                    bbox = bbox_.float().cuda()
                else:
                    bbox = bbox_
            else:
                
                img, label = img.float(),  label_.float()
                if len(bbox_[0]) > 0:
                    bbox = bbox_.float()
                else:
                    bbox = bbox_

            img, label = Variable(img), Variable(label)
            if len(bbox[0]) > 0:
                bbox = Variable(bbox)    
            else:
                bbox = np.asarray(bbox)
            
            #img, bbox, label = Variable(img), Variable(bbox), Variable(label)
            losses = trainer.train_step(img, bbox, label, scale)

            writer.add_scalars('training/losses', dict(total_loss=losses.total_loss,
                                                       roi_cls_loss=losses.roi_cls_loss,
                                                       roi_loc_loss=losses.roi_loc_loss,
                                                       rpn_cls_loss=losses.rpn_cls_loss,
                                                       rpn_loc_loss=losses.rpn_loc_loss), global_step)
            
            if (ii + 1) % opt.plot_every == 0:
                if os.path.exists(opt.debug_file):
                    ipdb.set_trace()

                # plot loss
                # trainer.vis.plot_many(trainer.get_meter_data())

                # plot ground truth bboxes
                ori_img_ = inverse_normalize(at.tonumpy(img[0]))
                gt_img = visdom_bbox(ori_img_,
                                     at.tonumpy(bbox_[0]),
                                     at.tonumpy(label_[0]),
                                     label_names=dataset.get_class_names()+['BG'])
                writer.add_image('gt_img', gt_img, global_step)

                # plot predicti bboxes
                _bboxes, _labels, _scores = trainer.faster_rcnn.predict([ori_img_], visualize=True)
                pred_img = visdom_bbox(ori_img_,
                                       at.tonumpy(_bboxes[0]),
                                       at.tonumpy(_labels[0]).reshape(-1),
                                       at.tonumpy(_scores[0]),
                                       label_names=dataset.get_class_names()+['BG'])
                writer.add_image('pred_img', pred_img, global_step)

                # rpn confusion matrix(meter)
                # trainer.vis.text(str(trainer.rpn_cm.value().tolist()), win='rpn_cm')
                # roi confusion matrix
                # trainer.vis.img('roi_cm', at.totensor(trainer.roi_cm.conf, False).float())
                
            if (global_step) % opt.snapshot_every == 0:
                snapshot_path = trainer.save(epoch=epoch, class_names=testset.get_class_names())
                print_log("Snapshotted to {}".format(snapshot_path))

        #snapshot_path = trainer.save(epoch=epoch)
        #print("After epoch {}: snapshotted to {}".format(epoch,snapshot_path))
        
        for lo in losses:
            del lo
        del img, bbox_, label_, scale
        torch.cuda.empty_cache()
        eval_result = eval(test_dataloader, faster_rcnn, trainer, testset, global_step, test_num=min(opt.test_num, len(testset)))
        print_log(eval_result)
        # TODO: this definitely is not good and will bias evaluation
        if eval_result['map'] > best_map:
            best_map = eval_result['map']
            best_path = trainer.save(best_map=eval_result['map'],epoch=epoch, class_names=testset.get_class_names())
            print_log("After epoch {}: snapshotted to {}".format(epoch, best_path))

        del eval_result
        torch.cuda.empty_cache()