first commit

ldm/guidance.py

@@ -0,0 +1,96 @@
+from typing import List, Tuple
+from scipy import interpolate
+import numpy as np
+import torch
+import matplotlib.pyplot as plt
+from IPython.display import clear_output
+import abc
+
+
+class GuideModel(torch.nn.Module, abc.ABC):
+    def __init__(self) -> None:
+        super().__init__()
+
+    @abc.abstractmethod
+    def preprocess(self, x_img):
+        pass
+
+    @abc.abstractmethod
+    def compute_loss(self, inp):
+        pass
+
+
+class Guider(torch.nn.Module):
+    def __init__(self, sampler, guide_model, scale=1.0, verbose=False):
+        """Apply classifier guidance
+
+        Specify a guidance scale as either a scalar
+        Or a schedule as a list of tuples t = 0->1 and scale, e.g.
+        [(0, 10), (0.5, 20), (1, 50)]
+        """
+        super().__init__()
+        self.sampler = sampler
+        self.index = 0
+        self.show = verbose
+        self.guide_model = guide_model
+        self.history = []
+
+        if isinstance(scale, (Tuple, List)):
+            times = np.array([x[0] for x in scale])
+            values = np.array([x[1] for x in scale])
+            self.scale_schedule = {"times": times, "values": values}
+        else:
+            self.scale_schedule = float(scale)
+
+        self.ddim_timesteps = sampler.ddim_timesteps
+        self.ddpm_num_timesteps = sampler.ddpm_num_timesteps
+
+
+    def get_scales(self):
+        if isinstance(self.scale_schedule, float):
+            return len(self.ddim_timesteps)*[self.scale_schedule]
+
+        interpolater = interpolate.interp1d(self.scale_schedule["times"], self.scale_schedule["values"])
+        fractional_steps = np.array(self.ddim_timesteps)/self.ddpm_num_timesteps
+        return interpolater(fractional_steps)
+
+    def modify_score(self, model, e_t, x, t, c):
+
+        # TODO look up index by t
+        scale = self.get_scales()[self.index]
+
+        if (scale == 0):
+            return e_t
+
+        sqrt_1ma = self.sampler.ddim_sqrt_one_minus_alphas[self.index].to(x.device)
+        with torch.enable_grad():
+            x_in = x.detach().requires_grad_(True)
+            pred_x0 = model.predict_start_from_noise(x_in, t=t, noise=e_t)
+            x_img = model.first_stage_model.decode((1/0.18215)*pred_x0)
+
+            inp = self.guide_model.preprocess(x_img)
+            loss = self.guide_model.compute_loss(inp)
+            grads = torch.autograd.grad(loss.sum(), x_in)[0]
+            correction = grads * scale
+
+            if self.show:
+                clear_output(wait=True)
+                print(loss.item(), scale, correction.abs().max().item(), e_t.abs().max().item())
+                self.history.append([loss.item(), scale, correction.min().item(), correction.max().item()])
+                plt.imshow((inp[0].detach().permute(1,2,0).clamp(-1,1).cpu()+1)/2)
+                plt.axis('off')
+                plt.show()
+                plt.imshow(correction[0][0].detach().cpu())
+                plt.axis('off')
+                plt.show()
+
+
+        e_t_mod = e_t - sqrt_1ma*correction
+        if self.show:
+            fig, axs = plt.subplots(1, 3)
+            axs[0].imshow(e_t[0][0].detach().cpu(), vmin=-2, vmax=+2)
+            axs[1].imshow(e_t_mod[0][0].detach().cpu(), vmin=-2, vmax=+2)
+            axs[2].imshow(correction[0][0].detach().cpu(), vmin=-2, vmax=+2)
+            plt.show()
+        self.index += 1
+        return e_t_mod