From 6fb3c9fdf866105482447190a11619721e4c6b34 Mon Sep 17 00:00:00 2001
From: Gard Spreemann <gspreemann@gmail.com>
Date: Wed, 24 Oct 2018 13:08:33 +0200
Subject: Initial commit of cleaned-up code.

---
 scnn/__init__.py  |  0
 scnn/chebyshev.py | 51 +++++++++++++++++++++++++++++++++++++++++++++++++++
 scnn/scnn.py      | 42 ++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 93 insertions(+)
 create mode 100644 scnn/__init__.py
 create mode 100644 scnn/chebyshev.py
 create mode 100644 scnn/scnn.py

diff --git a/scnn/__init__.py b/scnn/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/scnn/chebyshev.py b/scnn/chebyshev.py
new file mode 100644
index 0000000..8b5e086
--- /dev/null
+++ b/scnn/chebyshev.py
@@ -0,0 +1,51 @@
+import torch
+import scipy.sparse as sp
+import scipy.sparse.linalg as spl
+import numpy as np
+
+def normalize(L, half_interval = False):
+    assert(sp.isspmatrix(L))
+    M = L.shape[0]
+    assert(M == L.shape[1])
+    topeig = spl.eigsh(L, k=1, which="LM", return_eigenvectors = False)[0]   
+    #print("Topeig = %f" %(topeig))
+
+    ret = L.copy()
+    if half_interval:
+        ret *= 1.0/topeig
+    else:
+        ret *= 2.0/topeig
+        ret.setdiag(ret.diagonal(0) - np.ones(M), 0)
+
+    return ret
+
+def assemble(K, L, x):
+    (B, C_in, M) = x.shape
+    assert(L.shape[0] == M)
+    assert(L.shape[0] == L.shape[1])
+    assert(K > 0)
+    
+    X = []
+    for b in range(0, B):
+        X123 = []
+        for c_in in range(0, C_in):
+            X23 = []
+            X23.append(x[b, c_in, :].unsqueeze(1)) # Constant, k = 0 term.
+
+            if K > 1:
+                X23.append(L.mm(X23[0]))
+            for k in range(2, K):
+                X23.append(2*(L.mm(X23[k-1])) - X23[k-2])
+
+            X23 = torch.cat(X23, 1)
+            assert(X23.shape == (M, K))
+            X123.append(X23.unsqueeze(0))
+
+        X123 = torch.cat(X123, 0)
+        assert(X123.shape == (C_in, M, K))
+        X.append(X123.unsqueeze(0))
+
+    X = torch.cat(X, 0)
+    assert(X.shape == (B, C_in, M, K))
+
+    return X
diff --git a/scnn/scnn.py b/scnn/scnn.py
new file mode 100644
index 0000000..49efe71
--- /dev/null
+++ b/scnn/scnn.py
@@ -0,0 +1,42 @@
+import torch
+import torch.nn as nn
+import numpy as np
+import scipy.sparse as sp
+
+import chebyshev
+
+def coo2tensor(A):
+    assert(sp.isspmatrix_coo(A))
+    idxs = torch.LongTensor(np.vstack((A.row, A.col)))
+    vals = torch.FloatTensor(A.data)
+    return torch.sparse_coo_tensor(idxs, vals, size = A.shape, requires_grad = False)
+
+class SimplicialConvolution(nn.Module):
+    def __init__(self, K, L, C_in, C_out, groups = 1):
+        assert(groups == 1, "Only groups = 1 is currently supported.")
+        super().__init__()
+
+        assert(len(L.shape) == 2)
+        assert(L.shape[0] == L.shape[1])
+        assert(C_in > 0)
+        assert(C_out > 0)
+        assert(K > 0)
+        
+        self.M = L.shape[0]
+        self.C_in = C_in
+        self.C_out = C_out
+        self.K = K
+        self.L = L # Don't modify afterwards!
+
+        self.theta = nn.parameter.Parameter(torch.randn((self.C_out, self.C_in, self.K)))
+        
+    def forward(self, x):
+        (B, C_in, M) = x.shape
+        assert(M == self.M)
+        assert(C_in == self.C_in)
+
+        X = chebyshev.assemble(self.K, self.L, x)
+        y = torch.einsum("bimk,oik->bom", (X, self.theta))
+        assert(y.shape == (B, self.C_out, M))
+
+        return y
-- 
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