Add cm6 code

cm-code/biaffine.py

+#!/usr/bin/env python3
+
+import numpy as np
+
+n = 4
+d = 10
+
+Hhead = np.random.rand(n,d) # head vectors as rows
+Hdep  = np.random.rand(n,d) # dep  vectors as rows
+Uarc  = np.random.rand(d,d) # biaffine intermediate matrix
+uarc  = np.random.rand(d,1) # biaffine bias
+
+Sarc_original = Hhead @ Uarc @ Hdep.T + Hhead @ uarc
+#print(Sarc_original)
+
+ubias = np.vstack((Uarc.T, uarc.T)) # Uarc transposition not in paper, but not important since learned
+Hdepext = np.hstack((Hdep,np.ones((n, 1))))
+Sarc_simple = ((Hdepext @ ubias) @ Hhead.T).T # final transpose: dependents as columns
+#print(Sarc_simple)
+
+print(f"Original and simplified versions identical: {np.allclose(Sarc_original, Sarc_simple)}") # quality up to tolerance