ultralytics/nn/tasks.py

# Ultralytics YOLO 🚀, GPL-3.0 license

import contextlib
from copy import deepcopy

import thop
import torch
import torch.nn as nn

from ultralytics.nn.modules import (C1, C2, C3, C3TR, SPP, SPPF, Bottleneck, BottleneckCSP, C2f, C3Ghost, C3x, Classify,
                                    Concat, Conv, ConvTranspose, Detect, DWConv, DWConvTranspose2d, Ensemble, Focus,
                                    GhostBottleneck, GhostConv, Segment)
from ultralytics.yolo.utils import DEFAULT_CONFIG_DICT, DEFAULT_CONFIG_KEYS, LOGGER, colorstr, yaml_load
from ultralytics.yolo.utils.checks import check_yaml
from ultralytics.yolo.utils.torch_utils import (fuse_conv_and_bn, initialize_weights, intersect_dicts, make_divisible,
                                                model_info, scale_img, time_sync)


class BaseModel(nn.Module):
    '''
     The BaseModel class is a base class for all the models in the Ultralytics YOLO family.
    '''

    def forward(self, x, profile=False, visualize=False):
        """
        > `forward` is a wrapper for `_forward_once` that runs the model on a single scale

        Args:
          x: the input image
          profile: whether to profile the model. Defaults to False
          visualize: if True, will return the intermediate feature maps. Defaults to False

        Returns:
          The output of the network.
        """
        return self._forward_once(x, profile, visualize)

    def _forward_once(self, x, profile=False, visualize=False):
        """
        > Forward pass of the network

        Args:
          x: input to the model
          profile: if True, the time taken for each layer will be printed. Defaults to False
          visualize: If True, it will save the feature maps of the model. Defaults to False

        Returns:
          The last layer of the model.
        """
        y, dt = [], []  # outputs
        for m in self.model:
            if m.f != -1:  # if not from previous layer
                x = y[m.f] if isinstance(m.f, int) else [x if j == -1 else y[j] for j in m.f]  # from earlier layers
            if profile:
                self._profile_one_layer(m, x, dt)
            x = m(x)  # run
            y.append(x if m.i in self.save else None)  # save output
            if visualize:
                pass
                # TODO: feature_visualization(x, m.type, m.i, save_dir=visualize)
        return x

    def _profile_one_layer(self, m, x, dt):
        """
        It takes a model, an input, and a list of times, and it profiles the model on the input, appending
        the time to the list

        Args:
          m: the model
          x: the input image
          dt: list of time taken for each layer
        """
        c = m == self.model[-1]  # is final layer, copy input as inplace fix
        o = thop.profile(m, inputs=(x.copy() if c else x,), verbose=False)[0] / 1E9 * 2 if thop else 0  # FLOPs
        t = time_sync()
        for _ in range(10):
            m(x.copy() if c else x)
        dt.append((time_sync() - t) * 100)
        if m == self.model[0]:
            LOGGER.info(f"{'time (ms)':>10s} {'GFLOPs':>10s} {'params':>10s}  module")
        LOGGER.info(f'{dt[-1]:10.2f} {o:10.2f} {m.np:10.0f}  {m.type}')
        if c:
            LOGGER.info(f"{sum(dt):10.2f} {'-':>10s} {'-':>10s}  Total")

    def fuse(self):
        """
        > It takes a model and fuses the Conv2d() and BatchNorm2d() layers into a single layer

        Returns:
          The model is being returned.
        """
        LOGGER.info('Fusing layers... ')
        for m in self.model.modules():
            if isinstance(m, (Conv, DWConv)) and hasattr(m, 'bn'):
                m.conv = fuse_conv_and_bn(m.conv, m.bn)  # update conv
                delattr(m, 'bn')  # remove batchnorm
                m.forward = m.forward_fuse  # update forward
        self.info()
        return self

    def info(self, verbose=False, imgsz=640):
        """
        Prints model information

        Args:
          verbose: if True, prints out the model information. Defaults to False
          imgsz: the size of the image that the model will be trained on. Defaults to 640
        """
        model_info(self, verbose, imgsz)

    def _apply(self, fn):
        """
        `_apply()` is a function that applies a function to all the tensors in the model that are not
        parameters or registered buffers

        Args:
          fn: the function to apply to the model

        Returns:
          A model that is a Detect() object.
        """
        self = super()._apply(fn)
        m = self.model[-1]  # Detect()
        if isinstance(m, (Detect, Segment)):
            m.stride = fn(m.stride)
            m.anchors = fn(m.anchors)
            m.strides = fn(m.strides)
        return self

    def load(self, weights):
        """
        > This function loads the weights of the model from a file

        Args:
          weights: The weights to load into the model.
        """
        # Force all tasks to implement this function
        raise NotImplementedError("This function needs to be implemented by derived classes!")


class DetectionModel(BaseModel):
    # YOLOv5 detection model
    def __init__(self, cfg='yolov8n.yaml', ch=3, nc=None, verbose=True):  # model, input channels, number of classes
        super().__init__()
        self.yaml = cfg if isinstance(cfg, dict) else yaml_load(check_yaml(cfg), append_filename=True)  # cfg dict

        # Define model
        ch = self.yaml['ch'] = self.yaml.get('ch', ch)  # input channels
        if nc and nc != self.yaml['nc']:
            LOGGER.info(f"Overriding model.yaml nc={self.yaml['nc']} with nc={nc}")
            self.yaml['nc'] = nc  # override yaml value
        self.model, self.save = parse_model(deepcopy(self.yaml), ch=[ch], verbose=verbose)  # model, savelist
        self.names = {i: f'{i}' for i in range(self.yaml['nc'])}  # default names dict
        self.inplace = self.yaml.get('inplace', True)

        # Build strides
        m = self.model[-1]  # Detect()
        if isinstance(m, (Detect, Segment)):
            s = 256  # 2x min stride
            m.inplace = self.inplace
            forward = lambda x: self.forward(x)[0] if isinstance(m, Segment) else self.forward(x)
            m.stride = torch.tensor([s / x.shape[-2] for x in forward(torch.zeros(1, ch, s, s))])  # forward
            self.stride = m.stride
            m.bias_init()  # only run once

        # Init weights, biases
        initialize_weights(self)
        if verbose:
            self.info()
            LOGGER.info('')

    def forward(self, x, augment=False, profile=False, visualize=False):
        if augment:
            return self._forward_augment(x)  # augmented inference, None
        return self._forward_once(x, profile, visualize)  # single-scale inference, train

    def _forward_augment(self, x):
        img_size = x.shape[-2:]  # height, width
        s = [1, 0.83, 0.67]  # scales
        f = [None, 3, None]  # flips (2-ud, 3-lr)
        y = []  # outputs
        for si, fi in zip(s, f):
            xi = scale_img(x.flip(fi) if fi else x, si, gs=int(self.stride.max()))
            yi = self._forward_once(xi)[0]  # forward
            # cv2.imwrite(f'img_{si}.jpg', 255 * xi[0].cpu().numpy().transpose((1, 2, 0))[:, :, ::-1])  # save
            yi = self._descale_pred(yi, fi, si, img_size)
            y.append(yi)
        y = self._clip_augmented(y)  # clip augmented tails
        return torch.cat(y, -1), None  # augmented inference, train

    @staticmethod
    def _descale_pred(p, flips, scale, img_size, dim=1):
        # de-scale predictions following augmented inference (inverse operation)
        p[:, :4] /= scale  # de-scale
        x, y, wh, cls = p.split((1, 1, 2, p.shape[dim] - 4), dim)
        if flips == 2:
            y = img_size[0] - y  # de-flip ud
        elif flips == 3:
            x = img_size[1] - x  # de-flip lr
        return torch.cat((x, y, wh, cls), dim)

    def _clip_augmented(self, y):
        # Clip YOLOv5 augmented inference tails
        nl = self.model[-1].nl  # number of detection layers (P3-P5)
        g = sum(4 ** x for x in range(nl))  # grid points
        e = 1  # exclude layer count
        i = (y[0].shape[-1] // g) * sum(4 ** x for x in range(e))  # indices
        y[0] = y[0][..., :-i]  # large
        i = (y[-1].shape[-1] // g) * sum(4 ** (nl - 1 - x) for x in range(e))  # indices
        y[-1] = y[-1][..., i:]  # small
        return y

    def load(self, weights, verbose=True):
        csd = weights.float().state_dict()  # checkpoint state_dict as FP32
        csd = intersect_dicts(csd, self.state_dict())  # intersect
        self.load_state_dict(csd, strict=False)  # load
        if verbose:
            LOGGER.info(f'Transferred {len(csd)}/{len(self.model.state_dict())} items from pretrained weights')


class SegmentationModel(DetectionModel):
    # YOLOv5 segmentation model
    def __init__(self, cfg='yolov8n-seg.yaml', ch=3, nc=None, verbose=True):
        super().__init__(cfg, ch, nc, verbose)


class ClassificationModel(BaseModel):
    # YOLOv5 classification model
    def __init__(self,
                 cfg=None,
                 model=None,
                 ch=3,
                 nc=1000,
                 cutoff=10,
                 verbose=True):  # yaml, model, number of classes, cutoff index
        super().__init__()
        self._from_detection_model(model, nc, cutoff) if model is not None else self._from_yaml(cfg, ch, nc, verbose)

    def _from_detection_model(self, model, nc=1000, cutoff=10):
        # Create a YOLOv5 classification model from a YOLOv5 detection model
        from ultralytics.nn.autobackend import AutoBackend
        if isinstance(model, AutoBackend):
            model = model.model  # unwrap DetectMultiBackend
        model.model = model.model[:cutoff]  # backbone
        m = model.model[-1]  # last layer
        ch = m.conv.in_channels if hasattr(m, 'conv') else m.cv1.conv.in_channels  # ch into module
        c = Classify(ch, nc)  # Classify()
        c.i, c.f, c.type = m.i, m.f, 'models.common.Classify'  # index, from, type
        model.model[-1] = c  # replace
        self.model = model.model
        self.stride = model.stride
        self.save = []
        self.nc = nc

    def _from_yaml(self, cfg, ch, nc, verbose):
        self.yaml = cfg if isinstance(cfg, dict) else yaml_load(check_yaml(cfg), append_filename=True)  # cfg dict
        # Define model
        ch = self.yaml['ch'] = self.yaml.get('ch', ch)  # input channels
        if nc and nc != self.yaml['nc']:
            LOGGER.info(f"Overriding model.yaml nc={self.yaml['nc']} with nc={nc}")
            self.yaml['nc'] = nc  # override yaml value
        self.model, self.save = parse_model(deepcopy(self.yaml), ch=[ch], verbose=verbose)  # model, savelist
        self.names = {i: f'{i}' for i in range(self.yaml['nc'])}  # default names dict
        self.info()

    def load(self, weights):
        model = weights["model"] if isinstance(weights, dict) else weights  # torchvision models are not dicts
        csd = model.float().state_dict()
        csd = intersect_dicts(csd, self.state_dict())  # intersect
        self.load_state_dict(csd, strict=False)  # load

    @staticmethod
    def reshape_outputs(model, nc):
        # Update a TorchVision classification model to class count 'n' if required
        name, m = list((model.model if hasattr(model, 'model') else model).named_children())[-1]  # last module
        if isinstance(m, Classify):  # YOLO Classify() head
            if m.linear.out_features != nc:
                m.linear = nn.Linear(m.linear.in_features, nc)
        elif isinstance(m, nn.Linear):  # ResNet, EfficientNet
            if m.out_features != nc:
                setattr(model, name, nn.Linear(m.in_features, nc))
        elif isinstance(m, nn.Sequential):
            types = [type(x) for x in m]
            if nn.Linear in types:
                i = types.index(nn.Linear)  # nn.Linear index
                if m[i].out_features != nc:
                    m[i] = nn.Linear(m[i].in_features, nc)
            elif nn.Conv2d in types:
                i = types.index(nn.Conv2d)  # nn.Conv2d index
                if m[i].out_channels != nc:
                    m[i] = nn.Conv2d(m[i].in_channels, nc, m[i].kernel_size, m[i].stride, bias=m[i].bias is not None)


# Functions ------------------------------------------------------------------------------------------------------------


def attempt_load_weights(weights, device=None, inplace=True, fuse=False):
    # Loads an ensemble of models weights=[a,b,c] or a single model weights=[a] or weights=a
    from ultralytics.yolo.utils.downloads import attempt_download

    model = Ensemble()
    for w in weights if isinstance(weights, list) else [weights]:
        ckpt = torch.load(attempt_download(w), map_location='cpu')  # load
        args = {**DEFAULT_CONFIG_DICT, **ckpt['train_args']}  # combine model and default args, preferring model args
        ckpt = (ckpt.get('ema') or ckpt['model']).to(device).float()  # FP32 model

        # Model compatibility updates
        ckpt.args = {k: v for k, v in args.items() if k in DEFAULT_CONFIG_KEYS}  # attach args to model
        ckpt.pt_path = weights  # attach *.pt file path to model
        if not hasattr(ckpt, 'stride'):
            ckpt.stride = torch.tensor([32.])

        # Append
        model.append(ckpt.fuse().eval() if fuse and hasattr(ckpt, 'fuse') else ckpt.eval())  # model in eval mode

    # Module compatibility updates
    for m in model.modules():
        t = type(m)
        if t in (nn.Hardswish, nn.LeakyReLU, nn.ReLU, nn.ReLU6, nn.SiLU, Detect, Segment):
            m.inplace = inplace  # torch 1.7.0 compatibility
        elif t is nn.Upsample and not hasattr(m, 'recompute_scale_factor'):
            m.recompute_scale_factor = None  # torch 1.11.0 compatibility

    # Return model
    if len(model) == 1:
        return model[-1]

    # Return ensemble
    print(f'Ensemble created with {weights}\n')
    for k in 'names', 'nc', 'yaml':
        setattr(model, k, getattr(model[0], k))
    model.stride = model[torch.argmax(torch.tensor([m.stride.max() for m in model])).int()].stride  # max stride
    assert all(model[0].nc == m.nc for m in model), f'Models have different class counts: {[m.nc for m in model]}'
    return model


def attempt_load_one_weight(weight, device=None, inplace=True, fuse=False):
    # Loads a single model weights
    from ultralytics.yolo.utils.downloads import attempt_download

    ckpt = torch.load(attempt_download(weight), map_location='cpu')  # load
    args = {**DEFAULT_CONFIG_DICT, **ckpt['train_args']}  # combine model and default args, preferring model args
    model = (ckpt.get('ema') or ckpt['model']).to(device).float()  # FP32 model

    # Model compatibility updates
    model.args = {k: v for k, v in args.items() if k in DEFAULT_CONFIG_KEYS}  # attach args to model
    model.pt_path = weight  # attach *.pt file path to model
    if not hasattr(model, 'stride'):
        model.stride = torch.tensor([32.])

    model = model.fuse().eval() if fuse and hasattr(model, 'fuse') else model.eval()  # model in eval mode

    # Module compatibility updates
    for m in model.modules():
        t = type(m)
        if t in (nn.Hardswish, nn.LeakyReLU, nn.ReLU, nn.ReLU6, nn.SiLU, Detect, Segment):
            m.inplace = inplace  # torch 1.7.0 compatibility
        elif t is nn.Upsample and not hasattr(m, 'recompute_scale_factor'):
            m.recompute_scale_factor = None  # torch 1.11.0 compatibility

    # Return model and ckpt
    return model, ckpt


def parse_model(d, ch, verbose=True):  # model_dict, input_channels(3)
    # Parse a YOLO model.yaml dictionary
    if verbose:
        LOGGER.info(f"\n{'':>3}{'from':>20}{'n':>3}{'params':>10}  {'module':<45}{'arguments':<30}")
    nc, gd, gw, act = d['nc'], d['depth_multiple'], d['width_multiple'], d.get('activation')
    if act:
        Conv.default_act = eval(act)  # redefine default activation, i.e. Conv.default_act = nn.SiLU()
        if verbose:
            LOGGER.info(f"{colorstr('activation:')} {act}")  # print

    layers, save, c2 = [], [], ch[-1]  # layers, savelist, ch out
    for i, (f, n, m, args) in enumerate(d['backbone'] + d['head']):  # from, number, module, args
        m = eval(m) if isinstance(m, str) else m  # eval strings
        for j, a in enumerate(args):
            with contextlib.suppress(NameError):
                args[j] = eval(a) if isinstance(a, str) else a  # eval strings

        n = n_ = max(round(n * gd), 1) if n > 1 else n  # depth gain
        if m in {
                Classify, Conv, ConvTranspose, GhostConv, Bottleneck, GhostBottleneck, SPP, SPPF, DWConv, Focus,
                BottleneckCSP, C1, C2, C2f, C3, C3TR, C3Ghost, nn.ConvTranspose2d, DWConvTranspose2d, C3x}:
            c1, c2 = ch[f], args[0]
            if c2 != nc:  # if c2 not equal to number of classes (i.e. for Classify() output)
                c2 = make_divisible(c2 * gw, 8)

            args = [c1, c2, *args[1:]]
            if m in {BottleneckCSP, C1, C2, C2f, C3, C3TR, C3Ghost, C3x}:
                args.insert(2, n)  # number of repeats
                n = 1
        elif m is nn.BatchNorm2d:
            args = [ch[f]]
        elif m is Concat:
            c2 = sum(ch[x] for x in f)
        elif m in {Detect, Segment}:
            args.append([ch[x] for x in f])
            if m is Segment:
                args[2] = make_divisible(args[2] * gw, 8)
        else:
            c2 = ch[f]

        m_ = nn.Sequential(*(m(*args) for _ in range(n))) if n > 1 else m(*args)  # module
        t = str(m)[8:-2].replace('__main__.', '')  # module type
        m.np = sum(x.numel() for x in m_.parameters())  # number params
        m_.i, m_.f, m_.type = i, f, t  # attach index, 'from' index, type
        if verbose:
            LOGGER.info(f'{i:>3}{str(f):>20}{n_:>3}{m.np:10.0f}  {t:<45}{str(args):<30}')  # print
        save.extend(x % i for x in ([f] if isinstance(f, int) else f) if x != -1)  # append to savelist
        layers.append(m_)
        if i == 0:
            ch = []
        ch.append(c2)
    return nn.Sequential(*layers), sorted(save)