Source code for torchreid.engine.video.triplet

from __future__ import absolute_import
from __future__ import print_function
from __future__ import division

import time
import datetime

import torch

import torchreid
from torchreid.engine.image import ImageTripletEngine
from torchreid.engine.video import VideoSoftmaxEngine


class VideoTripletEngine(ImageTripletEngine, VideoSoftmaxEngine):
    """Triplet-loss engine for video-reid.

    Args:
        datamanager (DataManager): an instance of ``torchreid.data.ImageDataManager``
            or ``torchreid.data.VideoDataManager``.
        model (nn.Module): model instance.
        optimizer (Optimizer): an Optimizer.
        margin (float, optional): margin for triplet loss. Default is 0.3.
        weight_t (float, optional): weight for triplet loss. Default is 1.
        weight_x (float, optional): weight for softmax loss. Default is 1.
        scheduler (LRScheduler, optional): if None, no learning rate decay will be performed.
        use_cpu (bool, optional): use cpu. Default is False.
        label_smooth (bool, optional): use label smoothing regularizer. Default is True.
        pooling_method (str, optional): how to pool features for a tracklet.
            Default is "avg" (average). Choices are ["avg", "max"].

    Examples::
        
        import torch
        import torchreid
        # Each batch contains batch_size*seq_len images
        # Each identity is sampled with num_instances tracklets 
        datamanager = torchreid.data.VideoDataManager(
            root='path/to/reid-data',
            sources='mars',
            height=256,
            width=128,
            combineall=False,
            num_instances=4,
            train_sampler='RandomIdentitySampler'
            batch_size=8, # number of tracklets
            seq_len=15 # number of images in each tracklet
        )
        model = torchreid.models.build_model(
            name='resnet50',
            num_classes=datamanager.num_train_pids,
            loss='triplet'
        )
        model = model.cuda()
        optimizer = torchreid.optim.build_optimizer(
            model, optim='adam', lr=0.0003
        )
        scheduler = torchreid.optim.build_lr_scheduler(
            optimizer,
            lr_scheduler='single_step',
            stepsize=20
        )
        engine = torchreid.engine.VideoTripletEngine(
            datamanager, model, optimizer, margin=0.3,
            weight_t=0.7, weight_x=1, scheduler=scheduler,
            pooling_method='avg'
        )
        engine.run(
            max_epoch=60,
            save_dir='log/resnet50-triplet-mars',
            print_freq=10
        )
    """

    def __init__(self, datamanager, model, optimizer, margin=0.3,
                 weight_t=1, weight_x=1, scheduler=None, use_cpu=False,
                 label_smooth=True, pooling_method='avg'):
        super(VideoTripletEngine, self).__init__(datamanager, model, optimizer, margin=margin,
                                                 weight_t=weight_t, weight_x=weight_x,
                                                 scheduler=scheduler, use_cpu=use_cpu,
                                                 label_smooth=label_smooth)
        self.pooling_method = pooling_method