Compatibility with older pytorch versions

torch_dct/_dct.py

@@ -1,7 +1,30 @@
 import numpy as np
 import torch
 import torch.nn as nn
-import torch.fft
+
+try:
+    # PyTorch 1.7.0 and newer versions
+    import torch.fft
+
+    def dct1_rfft_impl(x):
+        return torch.view_as_real(torch.fft.rfft(x, dim=1))
+
+    def dct_fft_impl(v):
+        return torch.view_as_real(torch.fft.fft(v, dim=1))
+
+    def idct_irfft_impl(V):
+        return torch.fft.irfft(torch.view_as_complex(V), n=V.shape[1], dim=1)
+except ImportError:
+    # PyTorch 1.6.0 and older versions
+    def dct1_rfft_impl(x):
+        return torch.rfft(x, 1)
+
+    def dct_fft_impl(v):
+        return torch.rfft(v, 1, onesided=False)
+
+    def idct_irfft_impl(V):
+        return torch.irfft(V, 1, onesided=False)
+
 
 
 def dct1(x):
@@ -13,8 +36,9 @@ def dct1(x):
     """
     x_shape = x.shape
     x = x.view(-1, x_shape[-1])
+    x = torch.cat([x, x.flip([1])[:, 1:-1]], dim=1)
 
-    return torch.view_as_real(torch.fft.rfft(torch.cat([x, x.flip([1])[:, 1:-1]], dim=1), dim=1))[:, :, 0].view(*x_shape)
+    return dct1_rfft_impl(x)[:, :, 0].view(*x_shape)
 
 
 def idct1(X):
@@ -47,7 +71,7 @@ def dct(x, norm=None):
 
     v = torch.cat([x[:, ::2], x[:, 1::2].flip([1])], dim=1)
 
-    Vc = torch.view_as_real(torch.fft.fft(v, dim=1))
+    Vc = dct_fft_impl(v)
 
     k = - torch.arange(N, dtype=x.dtype, device=x.device)[None, :] * np.pi / (2 * N)
     W_r = torch.cos(k)
@@ -99,7 +123,7 @@ def idct(X, norm=None):
 
     V = torch.cat([V_r.unsqueeze(2), V_i.unsqueeze(2)], dim=2)
 
-    v = torch.fft.irfft(torch.view_as_complex(V), n=V.shape[1], dim=1)
+    v = idct_irfft_impl(V)
     x = v.new_zeros(v.shape)
     x[:, ::2] += v[:, :N - (N // 2)]
     x[:, 1::2] += v.flip([1])[:, :N // 2]