第一次完整测例跑完

src/unifolm_wma/utils/diffusion.py

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+import math
+import numpy as np
+import torch
+import torch.nn.functional as F
+from einops import repeat
+
+
+def timestep_embedding(timesteps, dim, max_period=10000, repeat_only=False):
+    """
+    Create sinusoidal timestep embeddings.
+    :param timesteps: a 1-D Tensor of N indices, one per batch element.
+                      These may be fractional.
+    :param dim: the dimension of the output.
+    :param max_period: controls the minimum frequency of the embeddings.
+    :return: an [N x dim] Tensor of positional embeddings.
+    """
+    if not repeat_only:
+        half = dim // 2
+        freqs = torch.exp(
+            -math.log(max_period) *
+            torch.arange(start=0, end=half, dtype=torch.float32) /
+            half).to(device=timesteps.device)
+        args = timesteps[:, None].float() * freqs[None]
+        embedding = torch.cat([torch.cos(args), torch.sin(args)], dim=-1)
+        if dim % 2:
+            embedding = torch.cat(
+                [embedding, torch.zeros_like(embedding[:, :1])], dim=-1)
+    else:
+        embedding = repeat(timesteps, 'b -> b d', d=dim)
+    return embedding
+
+
+def make_beta_schedule(schedule,
+                       n_timestep,
+                       linear_start=1e-4,
+                       linear_end=2e-2,
+                       cosine_s=8e-3):
+    if schedule == "linear":
+        betas = (torch.linspace(linear_start**0.5,
+                                linear_end**0.5,
+                                n_timestep,
+                                dtype=torch.float64)**2)
+
+    elif schedule == "cosine":
+        timesteps = (
+            torch.arange(n_timestep + 1, dtype=torch.float64) / n_timestep +
+            cosine_s)
+        alphas = timesteps / (1 + cosine_s) * np.pi / 2
+        alphas = torch.cos(alphas).pow(2)
+        alphas = alphas / alphas[0]
+        betas = 1 - alphas[1:] / alphas[:-1]
+        betas = np.clip(betas, a_min=0, a_max=0.999)
+
+    elif schedule == "sqrt_linear":
+        betas = torch.linspace(linear_start,
+                               linear_end,
+                               n_timestep,
+                               dtype=torch.float64)
+    elif schedule == "sqrt":
+        betas = torch.linspace(linear_start,
+                               linear_end,
+                               n_timestep,
+                               dtype=torch.float64)**0.5
+    else:
+        raise ValueError(f"schedule '{schedule}' unknown.")
+    return betas.numpy()
+
+
+def make_ddim_timesteps(ddim_discr_method,
+                        num_ddim_timesteps,
+                        num_ddpm_timesteps,
+                        verbose=True):
+    if ddim_discr_method == 'uniform':
+        c = num_ddpm_timesteps // num_ddim_timesteps
+        ddim_timesteps = np.asarray(list(range(0, num_ddpm_timesteps, c)))
+        steps_out = ddim_timesteps + 1
+    elif ddim_discr_method == 'uniform_trailing':
+        c = num_ddpm_timesteps / num_ddim_timesteps
+        ddim_timesteps = np.flip(np.round(np.arange(num_ddpm_timesteps, 0,
+                                                    -c))).astype(np.int64)
+        steps_out = ddim_timesteps - 1
+    elif ddim_discr_method == 'quad':
+        ddim_timesteps = ((np.linspace(0, np.sqrt(num_ddpm_timesteps * .8),
+                                       num_ddim_timesteps))**2).astype(int)
+        steps_out = ddim_timesteps + 1
+    else:
+        raise NotImplementedError(
+            f'There is no ddim discretization method called "{ddim_discr_method}"'
+        )
+
+    # assert ddim_timesteps.shape[0] == num_ddim_timesteps
+    # add one to get the final alpha values right (the ones from first scale to data during sampling)
+    # steps_out = ddim_timesteps + 1
+    if verbose:
+        print(f'Selected timesteps for ddim sampler: {steps_out}')
+    return steps_out
+
+
+def make_ddim_sampling_parameters(alphacums,
+                                  ddim_timesteps,
+                                  eta,
+                                  verbose=True):
+    # select alphas for computing the variance schedule
+    # print(f'ddim_timesteps={ddim_timesteps}, len_alphacums={len(alphacums)}')
+    alphas = alphacums[ddim_timesteps]
+    alphas_prev = np.asarray([alphacums[0]] +
+                             alphacums[ddim_timesteps[:-1]].tolist())
+
+    # according the formula provided in https://arxiv.org/abs/2010.02502
+    sigmas = eta * np.sqrt(
+        (1 - alphas_prev) / (1 - alphas) * (1 - alphas / alphas_prev))
+    if verbose:
+        print(
+            f'Selected alphas for ddim sampler: a_t: {alphas}; a_(t-1): {alphas_prev}'
+        )
+        print(
+            f'For the chosen value of eta, which is {eta}, '
+            f'this results in the following sigma_t schedule for ddim sampler {sigmas}'
+        )
+    return sigmas, alphas, alphas_prev
+
+
+def betas_for_alpha_bar(num_diffusion_timesteps, alpha_bar, max_beta=0.999):
+    """
+    Create a beta schedule that discretizes the given alpha_t_bar function,
+    which defines the cumulative product of (1-beta) over time from t = [0,1].
+    :param num_diffusion_timesteps: the number of betas to produce.
+    :param alpha_bar: a lambda that takes an argument t from 0 to 1 and
+                      produces the cumulative product of (1-beta) up to that
+                      part of the diffusion process.
+    :param max_beta: the maximum beta to use; use values lower than 1 to
+                     prevent singularities.
+    """
+    betas = []
+    for i in range(num_diffusion_timesteps):
+        t1 = i / num_diffusion_timesteps
+        t2 = (i + 1) / num_diffusion_timesteps
+        betas.append(min(1 - alpha_bar(t2) / alpha_bar(t1), max_beta))
+    return np.array(betas)
+
+
+def rescale_zero_terminal_snr(betas):
+    """
+    Rescales betas to have zero terminal SNR Based on https://arxiv.org/pdf/2305.08891.pdf (Algorithm 1)
+
+    Args:
+        betas (`numpy.ndarray`):
+            the betas that the scheduler is being initialized with.
+
+    Returns:
+        `numpy.ndarray`: rescaled betas with zero terminal SNR
+    """
+    # Convert betas to alphas_bar_sqrt
+    alphas = 1.0 - betas
+    alphas_cumprod = np.cumprod(alphas, axis=0)
+    alphas_bar_sqrt = np.sqrt(alphas_cumprod)
+
+    # Store old values.
+    alphas_bar_sqrt_0 = alphas_bar_sqrt[0].copy()
+    alphas_bar_sqrt_T = alphas_bar_sqrt[-1].copy()
+
+    # Shift so the last timestep is zero.
+    alphas_bar_sqrt -= alphas_bar_sqrt_T
+
+    # Scale so the first timestep is back to the old value.
+    alphas_bar_sqrt *= alphas_bar_sqrt_0 / (alphas_bar_sqrt_0 -
+                                            alphas_bar_sqrt_T)
+
+    # Convert alphas_bar_sqrt to betas
+    alphas_bar = alphas_bar_sqrt**2  # Revert sqrt
+    alphas = alphas_bar[1:] / alphas_bar[:-1]  # Revert cumprod
+    alphas = np.concatenate([alphas_bar[0:1], alphas])
+    betas = 1 - alphas
+
+    return betas
+
+
+def rescale_noise_cfg(noise_cfg, noise_pred_text, guidance_rescale=0.0):
+    """
+    Rescale `noise_cfg` according to `guidance_rescale`. Based on findings of [Common Diffusion Noise Schedules and
+    Sample Steps are Flawed](https://arxiv.org/pdf/2305.08891.pdf). See Section 3.4
+    """
+    std_text = noise_pred_text.std(dim=list(range(1, noise_pred_text.ndim)),
+                                   keepdim=True)
+    std_cfg = noise_cfg.std(dim=list(range(1, noise_cfg.ndim)), keepdim=True)
+    # Rescale the results from guidance (fixes overexposure)
+    noise_pred_rescaled = noise_cfg * (std_text / std_cfg)
+    # Mix with the original results from guidance by factor guidance_rescale to avoid "plain looking" images
+    noise_cfg = guidance_rescale * noise_pred_rescaled + (
+        1 - guidance_rescale) * noise_cfg
+    return noise_cfg