Update modeling_latent_diffusion.py

modeling_latent_diffusion.py

@@ -7,862 +7,17 @@ import torch
 import torch.nn as nn
 
 from diffusers import DiffusionPipeline
-from diffusers.configuration_utils import ConfigMixin
-from diffusers.modeling_utils import ModelMixin
-
-
-def get_timestep_embedding(timesteps, embedding_dim):
-    """
-    This matches the implementation in Denoising Diffusion Probabilistic Models:
-    From Fairseq.
-    Build sinusoidal embeddings.
-    This matches the implementation in tensor2tensor, but differs slightly
-    from the description in Section 3.5 of "Attention Is All You Need".
-    """
-    assert len(timesteps.shape) == 1
-
-    half_dim = embedding_dim // 2
-    emb = math.log(10000) / (half_dim - 1)
-    emb = torch.exp(torch.arange(half_dim, dtype=torch.float32) * -emb)
-    emb = emb.to(device=timesteps.device)
-    emb = timesteps.float()[:, None] * emb[None, :]
-    emb = torch.cat([torch.sin(emb), torch.cos(emb)], dim=1)
-    if embedding_dim % 2 == 1:  # zero pad
-        emb = torch.nn.functional.pad(emb, (0, 1, 0, 0))
-    return emb
-
-
-def nonlinearity(x):
-    # swish
-    return x * torch.sigmoid(x)
-
-
-def Normalize(in_channels):
-    return torch.nn.GroupNorm(num_groups=32, num_channels=in_channels, eps=1e-6, affine=True)
-
-
-class Upsample(nn.Module):
-    def __init__(self, in_channels, with_conv):
-        super().__init__()
-        self.with_conv = with_conv
-        if self.with_conv:
-            self.conv = torch.nn.Conv2d(in_channels, in_channels, kernel_size=3, stride=1, padding=1)
-
-    def forward(self, x):
-        x = torch.nn.functional.interpolate(x, scale_factor=2.0, mode="nearest")
-        if self.with_conv:
-            x = self.conv(x)
-        return x
-
-
-class Downsample(nn.Module):
-    def __init__(self, in_channels, with_conv):
-        super().__init__()
-        self.with_conv = with_conv
-        if self.with_conv:
-            # no asymmetric padding in torch conv, must do it ourselves
-            self.conv = torch.nn.Conv2d(in_channels, in_channels, kernel_size=3, stride=2, padding=0)
-
-    def forward(self, x):
-        if self.with_conv:
-            pad = (0, 1, 0, 1)
-            x = torch.nn.functional.pad(x, pad, mode="constant", value=0)
-            x = self.conv(x)
-        else:
-            x = torch.nn.functional.avg_pool2d(x, kernel_size=2, stride=2)
-        return x
-
-
-class ResnetBlock(nn.Module):
-    def __init__(self, *, in_channels, out_channels=None, conv_shortcut=False, dropout, temb_channels=512):
-        super().__init__()
-        self.in_channels = in_channels
-        out_channels = in_channels if out_channels is None else out_channels
-        self.out_channels = out_channels
-        self.use_conv_shortcut = conv_shortcut
-
-        self.norm1 = Normalize(in_channels)
-        self.conv1 = torch.nn.Conv2d(in_channels, out_channels, kernel_size=3, stride=1, padding=1)
-        if temb_channels > 0:
-            self.temb_proj = torch.nn.Linear(temb_channels, out_channels)
-        self.norm2 = Normalize(out_channels)
-        self.dropout = torch.nn.Dropout(dropout)
-        self.conv2 = torch.nn.Conv2d(out_channels, out_channels, kernel_size=3, stride=1, padding=1)
-        if self.in_channels != self.out_channels:
-            if self.use_conv_shortcut:
-                self.conv_shortcut = torch.nn.Conv2d(in_channels, out_channels, kernel_size=3, stride=1, padding=1)
-            else:
-                self.nin_shortcut = torch.nn.Conv2d(in_channels, out_channels, kernel_size=1, stride=1, padding=0)
-
-    def forward(self, x, temb):
-        h = x
-        h = self.norm1(h)
-        h = nonlinearity(h)
-        h = self.conv1(h)
-
-        if temb is not None:
-            h = h + self.temb_proj(nonlinearity(temb))[:, :, None, None]
-
-        h = self.norm2(h)
-        h = nonlinearity(h)
-        h = self.dropout(h)
-        h = self.conv2(h)
-
-        if self.in_channels != self.out_channels:
-            if self.use_conv_shortcut:
-                x = self.conv_shortcut(x)
-            else:
-                x = self.nin_shortcut(x)
-
-        return x + h
-
-
-class AttnBlock(nn.Module):
-    def __init__(self, in_channels):
-        super().__init__()
-        self.in_channels = in_channels
-
-        self.norm = Normalize(in_channels)
-        self.q = torch.nn.Conv2d(in_channels, in_channels, kernel_size=1, stride=1, padding=0)
-        self.k = torch.nn.Conv2d(in_channels, in_channels, kernel_size=1, stride=1, padding=0)
-        self.v = torch.nn.Conv2d(in_channels, in_channels, kernel_size=1, stride=1, padding=0)
-        self.proj_out = torch.nn.Conv2d(in_channels, in_channels, kernel_size=1, stride=1, padding=0)
-
-    def forward(self, x):
-        h_ = x
-        h_ = self.norm(h_)
-        q = self.q(h_)
-        k = self.k(h_)
-        v = self.v(h_)
-
-        # compute attention
-        b, c, h, w = q.shape
-        q = q.reshape(b, c, h * w)
-        q = q.permute(0, 2, 1)  # b,hw,c
-        k = k.reshape(b, c, h * w)  # b,c,hw
-        w_ = torch.bmm(q, k)  # b,hw,hw    w[b,i,j]=sum_c q[b,i,c]k[b,c,j]
-        w_ = w_ * (int(c) ** (-0.5))
-        w_ = torch.nn.functional.softmax(w_, dim=2)
-
-        # attend to values
-        v = v.reshape(b, c, h * w)
-        w_ = w_.permute(0, 2, 1)  # b,hw,hw (first hw of k, second of q)
-        h_ = torch.bmm(v, w_)  # b, c,hw (hw of q) h_[b,c,j] = sum_i v[b,c,i] w_[b,i,j]
-        h_ = h_.reshape(b, c, h, w)
-
-        h_ = self.proj_out(h_)
-
-        return x + h_
-
-
-class Model(nn.Module):
-    def __init__(
-        self,
-        *,
-        ch,
-        out_ch,
-        ch_mult=(1, 2, 4, 8),
-        num_res_blocks,
-        attn_resolutions,
-        dropout=0.0,
-        resamp_with_conv=True,
-        in_channels,
-        resolution,
-        use_timestep=True,
-    ):
-        super().__init__()
-        self.ch = ch
-        self.temb_ch = self.ch * 4
-        self.num_resolutions = len(ch_mult)
-        self.num_res_blocks = num_res_blocks
-        self.resolution = resolution
-        self.in_channels = in_channels
-
-        self.use_timestep = use_timestep
-        if self.use_timestep:
-            # timestep embedding
-            self.temb = nn.Module()
-            self.temb.dense = nn.ModuleList(
-                [
-                    torch.nn.Linear(self.ch, self.temb_ch),
-                    torch.nn.Linear(self.temb_ch, self.temb_ch),
-                ]
-            )
-
-        # downsampling
-        self.conv_in = torch.nn.Conv2d(in_channels, self.ch, kernel_size=3, stride=1, padding=1)
-
-        curr_res = resolution
-        in_ch_mult = (1,) + tuple(ch_mult)
-        self.down = nn.ModuleList()
-        for i_level in range(self.num_resolutions):
-            block = nn.ModuleList()
-            attn = nn.ModuleList()
-            block_in = ch * in_ch_mult[i_level]
-            block_out = ch * ch_mult[i_level]
-            for i_block in range(self.num_res_blocks):
-                block.append(
-                    ResnetBlock(
-                        in_channels=block_in, out_channels=block_out, temb_channels=self.temb_ch, dropout=dropout
-                    )
-                )
-                block_in = block_out
-                if curr_res in attn_resolutions:
-                    attn.append(AttnBlock(block_in))
-            down = nn.Module()
-            down.block = block
-            down.attn = attn
-            if i_level != self.num_resolutions - 1:
-                down.downsample = Downsample(block_in, resamp_with_conv)
-                curr_res = curr_res // 2
-            self.down.append(down)
-
-        # middle
-        self.mid = nn.Module()
-        self.mid.block_1 = ResnetBlock(
-            in_channels=block_in, out_channels=block_in, temb_channels=self.temb_ch, dropout=dropout
-        )
-        self.mid.attn_1 = AttnBlock(block_in)
-        self.mid.block_2 = ResnetBlock(
-            in_channels=block_in, out_channels=block_in, temb_channels=self.temb_ch, dropout=dropout
-        )
-
-        # upsampling
-        self.up = nn.ModuleList()
-        for i_level in reversed(range(self.num_resolutions)):
-            block = nn.ModuleList()
-            attn = nn.ModuleList()
-            block_out = ch * ch_mult[i_level]
-            skip_in = ch * ch_mult[i_level]
-            for i_block in range(self.num_res_blocks + 1):
-                if i_block == self.num_res_blocks:
-                    skip_in = ch * in_ch_mult[i_level]
-                block.append(
-                    ResnetBlock(
-                        in_channels=block_in + skip_in,
-                        out_channels=block_out,
-                        temb_channels=self.temb_ch,
-                        dropout=dropout,
-                    )
-                )
-                block_in = block_out
-                if curr_res in attn_resolutions:
-                    attn.append(AttnBlock(block_in))
-            up = nn.Module()
-            up.block = block
-            up.attn = attn
-            if i_level != 0:
-                up.upsample = Upsample(block_in, resamp_with_conv)
-                curr_res = curr_res * 2
-            self.up.insert(0, up)  # prepend to get consistent order
-
-        # end
-        self.norm_out = Normalize(block_in)
-        self.conv_out = torch.nn.Conv2d(block_in, out_ch, kernel_size=3, stride=1, padding=1)
-
-    def forward(self, x, t=None):
-        # assert x.shape[2] == x.shape[3] == self.resolution
-
-        if self.use_timestep:
-            # timestep embedding
-            assert t is not None
-            temb = get_timestep_embedding(t, self.ch)
-            temb = self.temb.dense[0](temb)
-            temb = nonlinearity(temb)
-            temb = self.temb.dense[1](temb)
-        else:
-            temb = None
-
-        # downsampling
-        hs = [self.conv_in(x)]
-        for i_level in range(self.num_resolutions):
-            for i_block in range(self.num_res_blocks):
-                h = self.down[i_level].block[i_block](hs[-1], temb)
-                if len(self.down[i_level].attn) > 0:
-                    h = self.down[i_level].attn[i_block](h)
-                hs.append(h)
-            if i_level != self.num_resolutions - 1:
-                hs.append(self.down[i_level].downsample(hs[-1]))
-
-        # middle
-        h = hs[-1]
-        h = self.mid.block_1(h, temb)
-        h = self.mid.attn_1(h)
-        h = self.mid.block_2(h, temb)
-
-        # upsampling
-        for i_level in reversed(range(self.num_resolutions)):
-            for i_block in range(self.num_res_blocks + 1):
-                h = self.up[i_level].block[i_block](torch.cat([h, hs.pop()], dim=1), temb)
-                if len(self.up[i_level].attn) > 0:
-                    h = self.up[i_level].attn[i_block](h)
-            if i_level != 0:
-                h = self.up[i_level].upsample(h)
-
-        # end
-        h = self.norm_out(h)
-        h = nonlinearity(h)
-        h = self.conv_out(h)
-        return h
-
-
-class Encoder(nn.Module):
-    def __init__(
-        self,
-        *,
-        ch,
-        out_ch,
-        ch_mult=(1, 2, 4, 8),
-        num_res_blocks,
-        attn_resolutions,
-        dropout=0.0,
-        resamp_with_conv=True,
-        in_channels,
-        resolution,
-        z_channels,
-        double_z=True,
-        **ignore_kwargs,
-    ):
-        super().__init__()
-        self.ch = ch
-        self.temb_ch = 0
-        self.num_resolutions = len(ch_mult)
-        self.num_res_blocks = num_res_blocks
-        self.resolution = resolution
-        self.in_channels = in_channels
-
-        # downsampling
-        self.conv_in = torch.nn.Conv2d(in_channels, self.ch, kernel_size=3, stride=1, padding=1)
-
-        curr_res = resolution
-        in_ch_mult = (1,) + tuple(ch_mult)
-        self.down = nn.ModuleList()
-        for i_level in range(self.num_resolutions):
-            block = nn.ModuleList()
-            attn = nn.ModuleList()
-            block_in = ch * in_ch_mult[i_level]
-            block_out = ch * ch_mult[i_level]
-            for i_block in range(self.num_res_blocks):
-                block.append(
-                    ResnetBlock(
-                        in_channels=block_in, out_channels=block_out, temb_channels=self.temb_ch, dropout=dropout
-                    )
-                )
-                block_in = block_out
-                if curr_res in attn_resolutions:
-                    attn.append(AttnBlock(block_in))
-            down = nn.Module()
-            down.block = block
-            down.attn = attn
-            if i_level != self.num_resolutions - 1:
-                down.downsample = Downsample(block_in, resamp_with_conv)
-                curr_res = curr_res // 2
-            self.down.append(down)
-
-        # middle
-        self.mid = nn.Module()
-        self.mid.block_1 = ResnetBlock(
-            in_channels=block_in, out_channels=block_in, temb_channels=self.temb_ch, dropout=dropout
-        )
-        self.mid.attn_1 = AttnBlock(block_in)
-        self.mid.block_2 = ResnetBlock(
-            in_channels=block_in, out_channels=block_in, temb_channels=self.temb_ch, dropout=dropout
-        )
-
-        # end
-        self.norm_out = Normalize(block_in)
-        self.conv_out = torch.nn.Conv2d(
-            block_in, 2 * z_channels if double_z else z_channels, kernel_size=3, stride=1, padding=1
-        )
-
-    def forward(self, x):
-        # assert x.shape[2] == x.shape[3] == self.resolution, "{}, {}, {}".format(x.shape[2], x.shape[3], self.resolution)
-
-        # timestep embedding
-        temb = None
-
-        # downsampling
-        hs = [self.conv_in(x)]
-        for i_level in range(self.num_resolutions):
-            for i_block in range(self.num_res_blocks):
-                h = self.down[i_level].block[i_block](hs[-1], temb)
-                if len(self.down[i_level].attn) > 0:
-                    h = self.down[i_level].attn[i_block](h)
-                hs.append(h)
-            if i_level != self.num_resolutions - 1:
-                hs.append(self.down[i_level].downsample(hs[-1]))
-
-        # middle
-        h = hs[-1]
-        h = self.mid.block_1(h, temb)
-        h = self.mid.attn_1(h)
-        h = self.mid.block_2(h, temb)
-
-        # end
-        h = self.norm_out(h)
-        h = nonlinearity(h)
-        h = self.conv_out(h)
-        return h
-
-
-class Decoder(nn.Module):
-    def __init__(
-        self,
-        *,
-        ch,
-        out_ch,
-        ch_mult=(1, 2, 4, 8),
-        num_res_blocks,
-        attn_resolutions,
-        dropout=0.0,
-        resamp_with_conv=True,
-        in_channels,
-        resolution,
-        z_channels,
-        give_pre_end=False,
-        **ignorekwargs,
-    ):
-        super().__init__()
-        self.ch = ch
-        self.temb_ch = 0
-        self.num_resolutions = len(ch_mult)
-        self.num_res_blocks = num_res_blocks
-        self.resolution = resolution
-        self.in_channels = in_channels
-        self.give_pre_end = give_pre_end
-
-        # compute in_ch_mult, block_in and curr_res at lowest res
-        in_ch_mult = (1,) + tuple(ch_mult)
-        block_in = ch * ch_mult[self.num_resolutions - 1]
-        curr_res = resolution // 2 ** (self.num_resolutions - 1)
-        self.z_shape = (1, z_channels, curr_res, curr_res)
-        print("Working with z of shape {} = {} dimensions.".format(self.z_shape, np.prod(self.z_shape)))
-
-        # z to block_in
-        self.conv_in = torch.nn.Conv2d(z_channels, block_in, kernel_size=3, stride=1, padding=1)
-
-        # middle
-        self.mid = nn.Module()
-        self.mid.block_1 = ResnetBlock(
-            in_channels=block_in, out_channels=block_in, temb_channels=self.temb_ch, dropout=dropout
-        )
-        self.mid.attn_1 = AttnBlock(block_in)
-        self.mid.block_2 = ResnetBlock(
-            in_channels=block_in, out_channels=block_in, temb_channels=self.temb_ch, dropout=dropout
-        )
-
-        # upsampling
-        self.up = nn.ModuleList()
-        for i_level in reversed(range(self.num_resolutions)):
-            block = nn.ModuleList()
-            attn = nn.ModuleList()
-            block_out = ch * ch_mult[i_level]
-            for i_block in range(self.num_res_blocks + 1):
-                block.append(
-                    ResnetBlock(
-                        in_channels=block_in, out_channels=block_out, temb_channels=self.temb_ch, dropout=dropout
-                    )
-                )
-                block_in = block_out
-                if curr_res in attn_resolutions:
-                    attn.append(AttnBlock(block_in))
-            up = nn.Module()
-            up.block = block
-            up.attn = attn
-            if i_level != 0:
-                up.upsample = Upsample(block_in, resamp_with_conv)
-                curr_res = curr_res * 2
-            self.up.insert(0, up)  # prepend to get consistent order
-
-        # end
-        self.norm_out = Normalize(block_in)
-        self.conv_out = torch.nn.Conv2d(block_in, out_ch, kernel_size=3, stride=1, padding=1)
-
-    def forward(self, z):
-        # assert z.shape[1:] == self.z_shape[1:]
-        self.last_z_shape = z.shape
-
-        # timestep embedding
-        temb = None
-
-        # z to block_in
-        h = self.conv_in(z)
-
-        # middle
-        h = self.mid.block_1(h, temb)
-        h = self.mid.attn_1(h)
-        h = self.mid.block_2(h, temb)
-
-        # upsampling
-        for i_level in reversed(range(self.num_resolutions)):
-            for i_block in range(self.num_res_blocks + 1):
-                h = self.up[i_level].block[i_block](h, temb)
-                if len(self.up[i_level].attn) > 0:
-                    h = self.up[i_level].attn[i_block](h)
-            if i_level != 0:
-                h = self.up[i_level].upsample(h)
-
-        # end
-        if self.give_pre_end:
-            return h
-
-        h = self.norm_out(h)
-        h = nonlinearity(h)
-        h = self.conv_out(h)
-        return h
-
-
-class VectorQuantizer(nn.Module):
-    """
-    Improved version over VectorQuantizer, can be used as a drop-in replacement. Mostly
-    avoids costly matrix multiplications and allows for post-hoc remapping of indices.
-    """
-
-    # NOTE: due to a bug the beta term was applied to the wrong term. for
-    # backwards compatibility we use the buggy version by default, but you can
-    # specify legacy=False to fix it.
-    def __init__(self, n_e, e_dim, beta, remap=None, unknown_index="random", sane_index_shape=False, legacy=True):
-        super().__init__()
-        self.n_e = n_e
-        self.e_dim = e_dim
-        self.beta = beta
-        self.legacy = legacy
-
-        self.embedding = nn.Embedding(self.n_e, self.e_dim)
-        self.embedding.weight.data.uniform_(-1.0 / self.n_e, 1.0 / self.n_e)
-
-        self.remap = remap
-        if self.remap is not None:
-            self.register_buffer("used", torch.tensor(np.load(self.remap)))
-            self.re_embed = self.used.shape[0]
-            self.unknown_index = unknown_index  # "random" or "extra" or integer
-            if self.unknown_index == "extra":
-                self.unknown_index = self.re_embed
-                self.re_embed = self.re_embed + 1
-            print(
-                f"Remapping {self.n_e} indices to {self.re_embed} indices. "
-                f"Using {self.unknown_index} for unknown indices."
-            )
-        else:
-            self.re_embed = n_e
-
-        self.sane_index_shape = sane_index_shape
-
-    def remap_to_used(self, inds):
-        ishape = inds.shape
-        assert len(ishape) > 1
-        inds = inds.reshape(ishape[0], -1)
-        used = self.used.to(inds)
-        match = (inds[:, :, None] == used[None, None, ...]).long()
-        new = match.argmax(-1)
-        unknown = match.sum(2) < 1
-        if self.unknown_index == "random":
-            new[unknown] = torch.randint(0, self.re_embed, size=new[unknown].shape).to(device=new.device)
-        else:
-            new[unknown] = self.unknown_index
-        return new.reshape(ishape)
-
-    def unmap_to_all(self, inds):
-        ishape = inds.shape
-        assert len(ishape) > 1
-        inds = inds.reshape(ishape[0], -1)
-        used = self.used.to(inds)
-        if self.re_embed > self.used.shape[0]:  # extra token
-            inds[inds >= self.used.shape[0]] = 0  # simply set to zero
-        back = torch.gather(used[None, :][inds.shape[0] * [0], :], 1, inds)
-        return back.reshape(ishape)
-
-    def forward(self, z, temp=None, rescale_logits=False, return_logits=False):
-        assert temp is None or temp == 1.0, "Only for interface compatible with Gumbel"
-        assert rescale_logits == False, "Only for interface compatible with Gumbel"
-        assert return_logits == False, "Only for interface compatible with Gumbel"
-        # reshape z -> (batch, height, width, channel) and flatten
-        z = rearrange(z, "b c h w -> b h w c").contiguous()
-        z_flattened = z.view(-1, self.e_dim)
-        # distances from z to embeddings e_j (z - e)^2 = z^2 + e^2 - 2 e * z
-
-        d = (
-            torch.sum(z_flattened**2, dim=1, keepdim=True)
-            + torch.sum(self.embedding.weight**2, dim=1)
-            - 2 * torch.einsum("bd,dn->bn", z_flattened, rearrange(self.embedding.weight, "n d -> d n"))
-        )
-
-        min_encoding_indices = torch.argmin(d, dim=1)
-        z_q = self.embedding(min_encoding_indices).view(z.shape)
-        perplexity = None
-        min_encodings = None
-
-        # compute loss for embedding
-        if not self.legacy:
-            loss = self.beta * torch.mean((z_q.detach() - z) ** 2) + torch.mean((z_q - z.detach()) ** 2)
-        else:
-            loss = torch.mean((z_q.detach() - z) ** 2) + self.beta * torch.mean((z_q - z.detach()) ** 2)
-
-        # preserve gradients
-        z_q = z + (z_q - z).detach()
-
-        # reshape back to match original input shape
-        z_q = rearrange(z_q, "b h w c -> b c h w").contiguous()
-
-        if self.remap is not None:
-            min_encoding_indices = min_encoding_indices.reshape(z.shape[0], -1)  # add batch axis
-            min_encoding_indices = self.remap_to_used(min_encoding_indices)
-            min_encoding_indices = min_encoding_indices.reshape(-1, 1)  # flatten
-
-        if self.sane_index_shape:
-            min_encoding_indices = min_encoding_indices.reshape(z_q.shape[0], z_q.shape[2], z_q.shape[3])
-
-        return z_q, loss, (perplexity, min_encodings, min_encoding_indices)
-
-    def get_codebook_entry(self, indices, shape):
-        # shape specifying (batch, height, width, channel)
-        if self.remap is not None:
-            indices = indices.reshape(shape[0], -1)  # add batch axis
-            indices = self.unmap_to_all(indices)
-            indices = indices.reshape(-1)  # flatten again
-
-        # get quantized latent vectors
-        z_q = self.embedding(indices)
-
-        if shape is not None:
-            z_q = z_q.view(shape)
-            # reshape back to match original input shape
-            z_q = z_q.permute(0, 3, 1, 2).contiguous()
-
-        return z_q
-
-
-class VQModel(ModelMixin, ConfigMixin):
-    def __init__(
-        self,
-        ch,
-        out_ch,
-        num_res_blocks,
-        attn_resolutions,
-        in_channels,
-        resolution,
-        z_channels,
-        n_embed,
-        embed_dim,
-        remap=None,
-        sane_index_shape=False,  # tell vector quantizer to return indices as bhw
-        ch_mult=(1, 2, 4, 8),
-        dropout=0.0,
-        double_z=True,
-        resamp_with_conv=True,
-        give_pre_end=False,
-    ):
-        super().__init__()
-
-        # register all __init__ params with self.register
-        self.register(
-            ch=ch,
-            out_ch=out_ch,
-            num_res_blocks=num_res_blocks,
-            attn_resolutions=attn_resolutions,
-            in_channels=in_channels,
-            resolution=resolution,
-            z_channels=z_channels,
-            n_embed=n_embed,
-            embed_dim=embed_dim,
-            remap=remap,
-            sane_index_shape=sane_index_shape,
-            ch_mult=ch_mult,
-            dropout=dropout,
-            double_z=double_z,
-            resamp_with_conv=resamp_with_conv,
-            give_pre_end=give_pre_end,
-        )
-
-        # pass init params to Encoder
-        self.encoder = Encoder(
-            ch=ch,
-            out_ch=out_ch,
-            num_res_blocks=num_res_blocks,
-            attn_resolutions=attn_resolutions,
-            in_channels=in_channels,
-            resolution=resolution,
-            z_channels=z_channels,
-            ch_mult=ch_mult,
-            dropout=dropout,
-            resamp_with_conv=resamp_with_conv,
-            double_z=double_z,
-            give_pre_end=give_pre_end,
-        )
-
-        self.quantize = VectorQuantizer(n_embed, embed_dim, beta=0.25, remap=remap, sane_index_shape=sane_index_shape)
-
-        # pass init params to Decoder
-        self.decoder = Decoder(
-            ch=ch,
-            out_ch=out_ch,
-            num_res_blocks=num_res_blocks,
-            attn_resolutions=attn_resolutions,
-            in_channels=in_channels,
-            resolution=resolution,
-            z_channels=z_channels,
-            ch_mult=ch_mult,
-            dropout=dropout,
-            resamp_with_conv=resamp_with_conv,
-            give_pre_end=give_pre_end,
-        )
-
-    def encode(self, x):
-        h = self.encoder(x)
-        h = self.quant_conv(h)
-        return h
-
-    def decode(self, h, force_not_quantize=False):
-        # also go through quantization layer
-        if not force_not_quantize:
-            quant, emb_loss, info = self.quantize(h)
-        else:
-            quant = h
-        quant = self.post_quant_conv(quant)
-        dec = self.decoder(quant)
-        return dec
-
-
-class DiagonalGaussianDistribution(object):
-    def __init__(self, parameters, deterministic=False):
-        self.parameters = parameters
-        self.mean, self.logvar = torch.chunk(parameters, 2, dim=1)
-        self.logvar = torch.clamp(self.logvar, -30.0, 20.0)
-        self.deterministic = deterministic
-        self.std = torch.exp(0.5 * self.logvar)
-        self.var = torch.exp(self.logvar)
-        if self.deterministic:
-            self.var = self.std = torch.zeros_like(self.mean).to(device=self.parameters.device)
-
-    def sample(self):
-        x = self.mean + self.std * torch.randn(self.mean.shape).to(device=self.parameters.device)
-        return x
-
-    def kl(self, other=None):
-        if self.deterministic:
-            return torch.Tensor([0.])
-        else:
-            if other is None:
-                return 0.5 * torch.sum(torch.pow(self.mean, 2)
-                                       + self.var - 1.0 - self.logvar,
-                                       dim=[1, 2, 3])
-            else:
-                return 0.5 * torch.sum(
-                    torch.pow(self.mean - other.mean, 2) / other.var
-                    + self.var / other.var - 1.0 - self.logvar + other.logvar,
-                    dim=[1, 2, 3])
-
-    def nll(self, sample, dims=[1,2,3]):
-        if self.deterministic:
-            return torch.Tensor([0.])
-        logtwopi = np.log(2.0 * np.pi)
-        return 0.5 * torch.sum(
-            logtwopi + self.logvar + torch.pow(sample - self.mean, 2) / self.var,
-            dim=dims)
-
-    def mode(self):
-        return self.mean
-
-class AutoencoderKL(ModelMixin, ConfigMixin):
-    def __init__(
-        self,
-        ch,
-        out_ch,
-        num_res_blocks,
-        attn_resolutions,
-        in_channels,
-        resolution,
-        z_channels,
-        embed_dim,
-        remap=None,
-        sane_index_shape=False,  # tell vector quantizer to return indices as bhw
-        ch_mult=(1, 2, 4, 8),
-        dropout=0.0,
-        double_z=True,
-        resamp_with_conv=True,
-        give_pre_end=False,
-    ):
-        super().__init__()
-
-        # register all __init__ params with self.register
-        self.register(
-            ch=ch,
-            out_ch=out_ch,
-            num_res_blocks=num_res_blocks,
-            attn_resolutions=attn_resolutions,
-            in_channels=in_channels,
-            resolution=resolution,
-            z_channels=z_channels,
-            embed_dim=embed_dim,
-            remap=remap,
-            sane_index_shape=sane_index_shape,
-            ch_mult=ch_mult,
-            dropout=dropout,
-            double_z=double_z,
-            resamp_with_conv=resamp_with_conv,
-            give_pre_end=give_pre_end,
-        )
-
-        # pass init params to Encoder
-        self.encoder = Encoder(
-            ch=ch,
-            out_ch=out_ch,
-            num_res_blocks=num_res_blocks,
-            attn_resolutions=attn_resolutions,
-            in_channels=in_channels,
-            resolution=resolution,
-            z_channels=z_channels,
-            ch_mult=ch_mult,
-            dropout=dropout,
-            resamp_with_conv=resamp_with_conv,
-            double_z=double_z,
-            give_pre_end=give_pre_end,
-        )
-
-        # pass init params to Decoder
-        self.decoder = Decoder(
-            ch=ch,
-            out_ch=out_ch,
-            num_res_blocks=num_res_blocks,
-            attn_resolutions=attn_resolutions,
-            in_channels=in_channels,
-            resolution=resolution,
-            z_channels=z_channels,
-            ch_mult=ch_mult,
-            dropout=dropout,
-            resamp_with_conv=resamp_with_conv,
-            give_pre_end=give_pre_end,
-        )
-
-        self.quant_conv = torch.nn.Conv2d(2*z_channels, 2*embed_dim, 1)
-        self.post_quant_conv = torch.nn.Conv2d(embed_dim, z_channels, 1)
-
-    def encode(self, x):
-        h = self.encoder(x)
-        moments = self.quant_conv(h)
-        posterior = DiagonalGaussianDistribution(moments)
-        return posterior
-
-    def decode(self, z):
-        z = self.post_quant_conv(z)
-        dec = self.decoder(z)
-        return dec
-
-    def forward(self, input, sample_posterior=True):
-        posterior = self.encode(input)
-        if sample_posterior:
-            z = posterior.sample()
-        else:
-            z = posterior.mode()
-        dec = self.decode(z)
-        return dec, posterior
 
+from .modeling_vae import AutoencoderKL
+from .configuration_ldmbert import LDMBertConfig
+from .modeling_ldmbert import LDMBertModel
 
 class LatentDiffusion(DiffusionPipeline):
     def __init__(self, vqvae, bert, tokenizer, unet, noise_scheduler):
         super().__init__()
         self.register_modules(vqvae=vqvae, bert=bert, tokenizer=tokenizer, unet=unet, noise_scheduler=noise_scheduler)
 
+    @torch.no_grad()
     def __call__(self, prompt, batch_size=1, generator=None, torch_device=None, eta=0.0, guidance_scale=1.0, num_inference_steps=50):
         # eta corresponds to η in paper and should be between [0, 1]
 
@@ -873,6 +28,7 @@ class LatentDiffusion(DiffusionPipeline):
         self.vqvae.to(torch_device)
         self.bert.to(torch_device)
         
+        # get unconditional embeddings for classifier free guidence
         if guidance_scale != 1.0:
             uncond_input = self.tokenizer([""], padding="max_length", max_length=77, return_tensors='pt').to(torch_device)
             uncond_embeddings = self.bert(uncond_input.input_ids)[0]
@@ -901,65 +57,42 @@ class LatentDiffusion(DiffusionPipeline):
         # - pred_image_direction -> "direction pointingc to x_t"
         # - pred_prev_image -> "x_t-1"
         for t in tqdm.tqdm(reversed(range(num_inference_steps)), total=num_inference_steps):
-            # 1. predict noise residual
+            # guidance_scale of 1 means no guidance
             if guidance_scale == 1.0:
-                timesteps = torch.tensor([inference_step_times[t]] * image.shape[0], device=torch_device)
-                context = text_embedding
                 image_in = image
+                context = text_embedding
+                timesteps = torch.tensor([inference_step_times[t]] * image.shape[0], device=torch_device)
             else:
+                # for classifier free guidance, we need to do two forward passes
+                # here we concanate embedding and unconditioned embedding in a single batch 
+                # to avoid doing two forward passes
                 image_in = torch.cat([image] * 2)
-                timesteps = torch.tensor([inference_step_times[t]] * image.shape[0], device=torch_device)
                 context = torch.cat([uncond_embeddings, text_embedding])
+                timesteps = torch.tensor([inference_step_times[t]] * image.shape[0], device=torch_device)
+
+            # 1. predict noise residual
+            pred_noise_t = self.unet(image_in, timesteps, context=context)
             
-            with torch.no_grad():
-                pred_noise_t = self.unet(image_in, timesteps, context=context)
-            
+            # perform guidance
             if guidance_scale != 1.0:
                 pred_noise_t_uncond, pred_noise_t = pred_noise_t.chunk(2)
                 pred_noise_t = pred_noise_t_uncond + guidance_scale * (pred_noise_t - pred_noise_t_uncond)
                     
-            # 2. get actual t and t-1
-            train_step = inference_step_times[t]
-            prev_train_step = inference_step_times[t - 1] if t > 0 else -1
-
-            # 3. compute alphas, betas
-            alpha_prod_t = self.noise_scheduler.get_alpha_prod(train_step)
-            alpha_prod_t_prev = self.noise_scheduler.get_alpha_prod(prev_train_step)
-            beta_prod_t = 1 - alpha_prod_t
-            beta_prod_t_prev = 1 - alpha_prod_t_prev
-
-            # 4. Compute predicted previous image from predicted noise
-            # First: compute predicted original image from predicted noise also called
-            # "predicted x_0" of formula (12) from https://arxiv.org/pdf/2010.02502.pdf
-            pred_original_image = (image - beta_prod_t.sqrt() * pred_noise_t) / alpha_prod_t.sqrt()
-
-            # Second: Clip "predicted x_0"
-#             pred_original_image = torch.clamp(pred_original_image, -1, 1)
+            # 2. predict previous mean of image x_t-1
+            pred_prev_image = self.noise_scheduler.compute_prev_image_step(pred_noise_t, image, t, num_inference_steps, eta)
 
-            # Third: Compute variance: "sigma_t(η)" -> see formula (16)
-            # σ_t = sqrt((1 − α_t−1)/(1 − α_t)) * sqrt(1 − α_t/α_t−1)
-            std_dev_t = (beta_prod_t_prev / beta_prod_t).sqrt() * (1 - alpha_prod_t / alpha_prod_t_prev).sqrt()
-            std_dev_t = eta * std_dev_t
-
-            # Fourth: Compute "direction pointing to x_t" of formula (12) from https://arxiv.org/pdf/2010.02502.pdf
-            pred_image_direction = (1 - alpha_prod_t_prev - std_dev_t**2).sqrt() * pred_noise_t
-
-            # Fifth: Compute x_t without "random noise" of formula (12) from https://arxiv.org/pdf/2010.02502.pdf
-            pred_prev_image = alpha_prod_t_prev.sqrt() * pred_original_image + pred_image_direction
-
-            # 5. Sample x_t-1 image optionally if η > 0.0 by adding noise to pred_prev_image
-            # Note: eta = 1.0 essentially corresponds to DDPM
-            if eta > 0.0:
+            # 3. optionally sample variance
+            variance = 0
+            if eta > 0:
                 noise = self.noise_scheduler.sample_noise(image.shape, device=image.device, generator=generator)
-                prev_image = pred_prev_image + std_dev_t * noise
-            else:
-                prev_image = pred_prev_image
+                variance = self.noise_scheduler.get_variance(t, num_inference_steps).sqrt() * eta * noise
 
-            # 6. Set current image to prev_image: x_t -> x_t-1
-            image = prev_image
+            # 4. set current image to prev_image: x_t -> x_t-1
+            image = pred_prev_image + variance
 
+        # scale and decode image with vae
         image = 1 /  0.18215 * image
         image = self.vqvae.decode(image)
         image = torch.clamp((image+1.0)/2.0, min=0.0, max=1.0)
 
-        return image
+        return image