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scheduler/scheduler.py

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+# Copyright 2024 The HuggingFace Team and The MeissonFlow Team. All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+import math
+from dataclasses import dataclass
+from typing import List, Optional, Tuple, Union
+
+import torch
+
+from diffusers.configuration_utils import ConfigMixin, register_to_config
+from diffusers.utils import BaseOutput
+from diffusers.schedulers.scheduling_utils import SchedulerMixin
+import torch.nn.functional as F
+
+def gumbel_noise(t, generator=None):
+    device = generator.device if generator is not None else t.device
+    noise = torch.zeros_like(t, device=device).uniform_(0, 1, generator=generator).to(t.device)
+    return -torch.log((-torch.log(noise.clamp(1e-20))).clamp(1e-20))
+
+
+def mask_by_random_topk(mask_len, probs, temperature=1.0, generator=None):
+    confidence = torch.log(probs.clamp(1e-20)) + temperature * gumbel_noise(probs, generator=generator)
+    sorted_confidence = torch.sort(confidence, dim=-1).values
+    cut_off = torch.gather(sorted_confidence, 1, mask_len.long())
+    masking = confidence < cut_off
+    return masking
+
+
+@dataclass
+class SchedulerOutput(BaseOutput):
+    """
+    Output class for the scheduler's `step` function output.
+
+    Args:
+        prev_sample (`torch.Tensor` of shape `(batch_size, num_channels, height, width)` for images):
+            Computed sample `(x_{t-1})` of previous timestep. `prev_sample` should be used as next model input in the
+            denoising loop.
+        pred_original_sample (`torch.Tensor` of shape `(batch_size, num_channels, height, width)` for images):
+            The predicted denoised sample `(x_{0})` based on the model output from the current timestep.
+            `pred_original_sample` can be used to preview progress or for guidance.
+    """
+
+    prev_sample: torch.Tensor
+    pred_original_sample: torch.Tensor = None
+
+
+class Scheduler(SchedulerMixin, ConfigMixin):
+    order = 1
+
+    temperatures: torch.Tensor
+
+    @register_to_config
+    def __init__(
+        self,
+        mask_token_id: int,
+        masking_schedule: str = "cosine",
+    ):
+        self.temperatures = None
+        self.timesteps = None
+
+    def set_timesteps(
+        self,
+        num_inference_steps: int,
+        temperature: Union[int, Tuple[int, int], List[int]] = (2, 0),
+        device: Union[str, torch.device] = None,
+    ):
+        self.timesteps = torch.arange(num_inference_steps, device=device).flip(0)
+
+        if isinstance(temperature, (tuple, list)):
+            self.temperatures = torch.linspace(temperature[0], temperature[1], num_inference_steps, device=device)
+        else:
+            self.temperatures = torch.linspace(temperature, 0.01, num_inference_steps, device=device)
+
+
+    ### from https://huggingface.co/transformers/v3.2.0/_modules/transformers/generation_utils.html
+    def top_k_top_p_filtering(
+        self,
+        logits,
+        top_k: int = 0,
+        top_p: float = 1.0,
+        filter_value: float = -float("Inf"),
+        min_tokens_to_keep: int = 1,
+    ):
+        """Filter a distribution of logits using top-k and/or nucleus (top-p) filtering
+        Args:
+            logits: logits distribution shape (batch size, vocabulary size)
+            if top_k > 0: keep only top k tokens with highest probability (top-k filtering).
+            if top_p < 1.0: keep the top tokens with cumulative probability >= top_p (nucleus filtering).
+                Nucleus filtering is described in Holtzman et al. (http://arxiv.org/abs/1904.09751)
+            Make sure we keep at least min_tokens_to_keep per batch example in the output
+        From: https://gist.github.com/thomwolf/1a5a29f6962089e871b94cbd09daf317
+        """
+        if top_k > 0:
+            top_k = min(max(top_k, min_tokens_to_keep), logits.size(-1)) 
+            indices_to_remove = logits < torch.topk(logits, top_k)[0][..., -1, None]
+            logits[indices_to_remove] = filter_value
+
+        if top_p < 1.0:
+            sorted_logits, sorted_indices = torch.sort(logits, descending=True)
+            cumulative_probs = torch.cumsum(F.softmax(sorted_logits, dim=-1), dim=-1)
+
+           
+            sorted_indices_to_remove = cumulative_probs > top_p
+            if min_tokens_to_keep > 1:
+                sorted_indices_to_remove[..., :min_tokens_to_keep] = 0
+            sorted_indices_to_remove[..., 1:] = sorted_indices_to_remove[..., :-1].clone()
+            sorted_indices_to_remove[..., 0] = 0
+
+            indices_to_remove = torch.zeros_like(logits, dtype=torch.bool).scatter_(-1, sorted_indices, sorted_indices_to_remove)
+            logits[indices_to_remove] = filter_value
+
+        return logits
+
+
+    def step(
+        self,
+        model_output: torch.Tensor,
+        timestep: torch.long,
+        sample: torch.LongTensor,
+        starting_mask_ratio: int = 1,
+        generator: Optional[torch.Generator] = None,
+        return_dict: bool = True,
+        using_topk_topp: Optional[bool] = False,
+        sampling_temperature: Optional[float] = 1.0,
+    ) -> Union[SchedulerOutput, Tuple]:
+        two_dim_input = sample.ndim == 3 and model_output.ndim == 4
+
+        if two_dim_input:
+            batch_size, codebook_size, height, width = model_output.shape
+            sample = sample.reshape(batch_size, height * width)
+            model_output = model_output.reshape(batch_size, codebook_size, height * width).permute(0, 2, 1)
+
+        unknown_map = sample == self.config.mask_token_id
+
+        if using_topk_topp:
+            model_output = model_output / max(sampling_temperature, 1e-5)
+
+        if using_topk_topp:
+            top_k=8192
+            top_p=0.2
+            if top_k > 0 or top_p < 1.0:
+                model_output = self.top_k_top_p_filtering(model_output, top_k=top_k, top_p=top_p)
+
+        probs = model_output.softmax(dim=-1)
+
+        device = probs.device
+        probs_ = probs.to(generator.device) if generator is not None else probs  # handles when generator is on CPU
+        if probs_.device.type == "cpu" and probs_.dtype != torch.float32:
+            probs_ = probs_.float()  # multinomial is not implemented for cpu half precision
+        probs_ = probs_.reshape(-1, probs.size(-1))
+        pred_original_sample = torch.multinomial(probs_, 1, generator=generator).to(device=device)
+        pred_original_sample = pred_original_sample[:, 0].view(*probs.shape[:-1])
+        pred_original_sample = torch.where(unknown_map, pred_original_sample, sample)
+
+        if timestep == 0:
+            prev_sample = pred_original_sample
+        else:
+            seq_len = sample.shape[1]
+            step_idx = (self.timesteps == timestep).nonzero()
+            ratio = (step_idx + 1) / len(self.timesteps)
+
+            if self.config.masking_schedule == "cosine":
+                mask_ratio = torch.cos(ratio * math.pi / 2)
+            elif self.config.masking_schedule == "linear":
+                mask_ratio = 1 - ratio
+            else:
+                raise ValueError(f"unknown masking schedule {self.config.masking_schedule}")
+
+            mask_ratio = starting_mask_ratio * mask_ratio
+
+            mask_len = (seq_len * mask_ratio).floor()
+            # do not mask more than amount previously masked
+            mask_len = torch.min(unknown_map.sum(dim=-1, keepdim=True) - 1, mask_len)
+            # mask at least one
+            mask_len = torch.max(torch.tensor([1], device=model_output.device), mask_len)
+
+            selected_probs = torch.gather(probs, -1, pred_original_sample[:, :, None])[:, :, 0]
+            # Ignores the tokens given in the input by overwriting their confidence.
+            selected_probs = torch.where(unknown_map, selected_probs, torch.finfo(selected_probs.dtype).max)
+
+            masking = mask_by_random_topk(mask_len, selected_probs, self.temperatures[step_idx], generator)
+
+            # Masks tokens with lower confidence.
+            prev_sample = torch.where(masking, self.config.mask_token_id, pred_original_sample)
+
+        if two_dim_input:
+            prev_sample = prev_sample.reshape(batch_size, height, width)
+            pred_original_sample = pred_original_sample.reshape(batch_size, height, width)
+
+        if not return_dict:
+            return (prev_sample, pred_original_sample)
+
+        return SchedulerOutput(prev_sample, pred_original_sample)
+
+    def add_noise(self, sample, timesteps, generator=None):
+        step_idx = (self.timesteps == timesteps).nonzero()
+        ratio = (step_idx + 1) / len(self.timesteps)
+
+        if self.config.masking_schedule == "cosine":
+            mask_ratio = torch.cos(ratio * math.pi / 2)
+        elif self.config.masking_schedule == "linear":
+            mask_ratio = 1 - ratio
+        else:
+            raise ValueError(f"unknown masking schedule {self.config.masking_schedule}")
+
+        mask_indices = (
+            torch.rand(
+                sample.shape, device=generator.device if generator is not None else sample.device, generator=generator
+            ).to(sample.device)
+            < mask_ratio
+        )
+
+        masked_sample = sample.clone()
+
+        masked_sample[mask_indices] = self.config.mask_token_id
+
+        return masked_sample