first commit

ldm/models/diffusion/sampling_util.py

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+import torch
+import numpy as np
+
+
+def append_dims(x, target_dims):
+    """Appends dimensions to the end of a tensor until it has target_dims dimensions.
+    From https://github.com/crowsonkb/k-diffusion/blob/master/k_diffusion/utils.py"""
+    dims_to_append = target_dims - x.ndim
+    if dims_to_append < 0:
+        raise ValueError(f'input has {x.ndim} dims but target_dims is {target_dims}, which is less')
+    return x[(...,) + (None,) * dims_to_append]
+
+
+def renorm_thresholding(x0, value):
+    # renorm
+    pred_max = x0.max()
+    pred_min = x0.min()
+    pred_x0 = (x0 - pred_min) / (pred_max - pred_min)  # 0 ... 1
+    pred_x0 = 2 * pred_x0 - 1.  # -1 ... 1
+
+    s = torch.quantile(
+        rearrange(pred_x0, 'b ... -> b (...)').abs(),
+        value,
+        dim=-1
+    )
+    s.clamp_(min=1.0)
+    s = s.view(-1, *((1,) * (pred_x0.ndim - 1)))
+
+    # clip by threshold
+    # pred_x0 = pred_x0.clamp(-s, s) / s  # needs newer pytorch  # TODO bring back to pure-gpu with min/max
+
+    # temporary hack: numpy on cpu
+    pred_x0 = np.clip(pred_x0.cpu().numpy(), -s.cpu().numpy(), s.cpu().numpy()) / s.cpu().numpy()
+    pred_x0 = torch.tensor(pred_x0).to(self.model.device)
+
+    # re.renorm
+    pred_x0 = (pred_x0 + 1.) / 2.  # 0 ... 1
+    pred_x0 = (pred_max - pred_min) * pred_x0 + pred_min  # orig range
+    return pred_x0
+
+
+def norm_thresholding(x0, value):
+    s = append_dims(x0.pow(2).flatten(1).mean(1).sqrt().clamp(min=value), x0.ndim)
+    return x0 * (value / s)
+
+
+def spatial_norm_thresholding(x0, value):
+    # b c h w
+    s = x0.pow(2).mean(1, keepdim=True).sqrt().clamp(min=value)
+    return x0 * (value / s)