Generating 3D divergence matrix: getDIV.py

Some funtions for sparse matrix: sputils.py -> Updated we've discussed before
Test example for divergence

code/sputils.py

@@ -0,0 +1,18 @@
+import numpy as np
+from scipy import sparse
+
+def ddx(n):
+    """Define 1D derivatives"""
+    return sparse.spdiags((np.ones((n+1,1))*[-1,1]).T, [0,1], n, n+1)
+    
+def sdiag(h):
+    """Sparse diagonal matrix"""
+    return sparse.spdiags(h, 0, np.size(h), np.size(h))    
+
+def speye(n):
+    """Sparse identity"""
+    return sparse.identity(n)
+
+def kron3(A, B, C):
+    """Two kron prods"""
+    return sparse.kron(sparse.kron(A, B), C)