modeling.py

import torch
from torch import nn
import torch.nn.functional as F
import math
from huggingface_hub import PyTorchModelHubMixin

def timestep_embedding(tsteps, emb_dim, max_period= 10000):
    exponent = -math.log(max_period) * torch.linspace(0, 1, emb_dim//2, device=tsteps.device)
    emb = tsteps[:,None].float() * exponent.exp()[None,:]
    emb = torch.cat([emb.sin(), emb.cos()], dim=-1)
    return F.pad(emb, (0,1,0,0)) if emb_dim%2==1 else emb

def lin(ni,nf,act=nn.SiLU,norm=None,bias=True):
    layers = nn.Sequential()
    if norm:
        layers.append(norm(ni))
    if act:
        layers.append(act())
    layers.append(nn.Linear(ni,nf,bias=bias))
    return layers

def unet_conv(ni,nf,act=nn.SiLU,norm=None,bias=True,ks=3,stride=1):
    layers = nn.Sequential()
    if norm:
        layers.append(norm(ni))
    if act:
        layers.append(act())
    layers.append(nn.Conv2d(ni,nf,kernel_size=ks,stride=stride,padding=ks//2,bias=bias))
    return layers

class EmbResBlock(nn.Module):
    def __init__(self, n_emb,ni,nf,act=nn.SiLU,norm=nn.BatchNorm2d,bias=True,ks=3):
        super().__init__()
        if nf is None:
            nf = ni
        self.emb_proj = nn.Linear(n_emb,nf*2)
        self.conv1 = unet_conv(ni,nf,norm=norm,act=act,ks=ks)
        self.conv2 = unet_conv(nf,nf,norm=norm,act=act,ks=ks)
        self.idconv = nn.Identity() if ni==nf else nn.Conv2d(ni,nf,1)

    def forward(self,x,t):
        inp = x
        emb = self.emb_proj(F.silu(t))[:, :, None, None]
        x = self.conv1(x)
        scale,shift = torch.chunk(emb,2,dim=1)
        x = x*(1+scale) + shift
        x= self.conv2(x)

        return x + self.idconv(inp)
    
from functools import wraps

def saved(m, blk):
    m_ = m.forward

    @wraps(m.forward)
    def _f(*args, **kwargs):
        res = m_(*args, **kwargs)
        blk.saved.append(res)
        return res

    m.forward = _f
    return m

class DownBlock(nn.Module):
    def __init__(self, n_emb,ni,nf,add_down,num_layers=1):
        super().__init__()
        self.resnets =nn.ModuleList([saved(EmbResBlock(n_emb,ni if i ==0 else nf,nf),self) for i in range(num_layers)])
        if add_down:
            self.down = saved(nn.Conv2d(nf, nf, 3, stride=2, padding=1),self)
        else:
            self.down = nn.Identity()

    def forward(self,x,t):
        self.saved = []
        for resnet in self.resnets:
            x = resnet(x,t)
        x= self.down(x)

        return x 
    
def upsample(nf): return nn.Sequential(nn.Upsample(scale_factor=2.), nn.Conv2d(nf, nf, 3, padding=1))

class UpBlock(nn.Module):
    def __init__(self, n_emb,ni,prev_nf,nf,add_up,num_layers = 1):
        super().__init__()
        self.resnets = nn.ModuleList([EmbResBlock(n_emb,(prev_nf if i==0 else nf)+(ni if (i==num_layers-1) else nf),nf) for i in range(num_layers)])
        self.up = upsample(nf) if add_up else nn.Identity()

    def forward(self,x,t,ups):
        for resnet in self.resnets:
            x= resnet(torch.cat([x,ups.pop()],dim=1),t)
        x = self.up(x)

        return x
    
class EmbUnetModel(nn.Module, PyTorchModelHubMixin):
    def __init__(self, in_channels =1,out_channels=1,nfs=(32,64,128,256),n_layers=2):
        super().__init__()
        self.conv_in = nn.Conv2d(in_channels,nfs[0],kernel_size=3,padding=1)
        self.n_temb = nf = nfs[0]
        n_emb = nf*4
        self.cond_emb = nn.Embedding(10, n_emb)
        self.mlp_emb = nn.Sequential(lin(self.n_temb,n_emb,norm=nn.BatchNorm1d),lin(n_emb,n_emb))

        self.downs = nn.ModuleList()

        for i in range(len(nfs)):
            ni=nf
            nf= nfs[i]
            self.downs.append(DownBlock(n_emb,ni,nf,add_down=i!=len(nfs)-1,num_layers=n_layers))

        self.mid_block = EmbResBlock(n_emb,ni=nfs[-1],nf=None)

        rev_nfs = list(reversed(nfs))
        nf= rev_nfs[0]
        self.ups = nn.ModuleList()
        for i in range(len(rev_nfs)):
            prev_nf =nf
            nf = rev_nfs[i]
            ni = rev_nfs[min(i+1, len(nfs)-1)]
            self.ups.append(UpBlock(n_emb, ni, prev_nf, nf, add_up=i!=len(nfs)-1, num_layers=n_layers+1))

        self.conv_out = unet_conv(ni=nfs[0],nf=out_channels,norm=nn.BatchNorm2d,act=nn.SiLU,bias=False)

    def forward(self,inp):
        x,t,c = inp
        temb = timestep_embedding(t,self.n_temb)
        emb = self.mlp_emb(temb) + self.cond_emb(c)
        x = self.conv_in(x)
        saved = [x]
        for block in self.downs:
            x= block(x,emb)
        saved += [p for o in self.downs for p in o.saved]
        x = self.mid_block(x, emb)
        for block in self.ups: x = block(x, emb, saved)
        return self.conv_out(x)
    
import torch
import matplotlib.pyplot as plt
import torchvision.transforms.functional as TF

# All labels from dataset
LABELS = [
    'T-shirt/top',
    'Trouser',
    'Pullover',
    'Dress',
    'Coat',
    'Sandal',
    'Shirt',
    'Sneaker',
    'Bag',
    'Ankle boot'
]

def sigmas_karras(n, sigma_min=0.01, sigma_max=80., rho=7.):
    ramp = torch.linspace(0, 1, n)
    min_inv_rho = sigma_min**(1/rho)
    max_inv_rho = sigma_max**(1/rho)
    sigmas = (max_inv_rho + ramp * (min_inv_rho-max_inv_rho))**rho
    return torch.cat([sigmas, torch.tensor([0.])])

def scalings(sig, sig_data=0.66):
    totvar = sig**2 + sig_data**2
    c_skip = sig_data**2 / totvar
    c_out = sig * sig_data / totvar.sqrt()
    c_in  = 1 / totvar.sqrt()
    return c_skip, c_out, c_in

def denoise(model, x, sig, label, device):
    sig = sig[None].to(device)
    c_skip, c_out, c_in = scalings(sig)
    return model((x * c_in, sig, torch.tensor([label], device=device))) * c_out + x * c_skip

@torch.no_grad()
def sample_euler(x, sigs, i, model, label, device):
    sig, sig2 = sigs[i], sigs[i+1]
    denoised = denoise(model, x, sig, label, device)
    return x + (x - denoised) / sig * (sig2 - sig)

def generate(class_name, model, steps=100, sigma_max=80., device=None):

    if device is None:
        device = 'cuda' if torch.cuda.is_available() else 'cpu'
    
    class_name_normalized = class_name.strip().lower()
    
    label_idx = None
    for idx, label in enumerate(LABELS):
        if label.lower() == class_name_normalized:
            label_idx = idx
            break
    
    if label_idx is None:
        available = "\n".join([f"  {i}: {name}" for i, name in enumerate(LABELS)])
        raise ValueError(
            f"Invalid class name: '{class_name}'\n\n"
            f"Available classes:\n{available}"
        )
    
    model.eval()
    model.to(device)
    
    x = torch.randn(1, 1, 32, 32).to(device) * sigma_max
    
    sigs = sigmas_karras(steps, sigma_max=sigma_max).to(device)
    
    for i in range(len(sigs) - 1):
        x = sample_euler(x, sigs, i, model, label_idx, device)
    
    return x.squeeze(0).cpu()


def show_image(image_tensor):
    """
    Display a generated image.
    
    Args:
        image_tensor: Tensor of shape [1, 32, 32] or [32, 32]
    """
    if image_tensor.dim() == 3:
        image_tensor = image_tensor.squeeze(0)
    
    plt.figure(figsize=(4, 4))
    plt.imshow(image_tensor, cmap='gray', vmin=-1, vmax=1)
    plt.axis('off')
    plt.tight_layout()
    plt.show()