Put utils in their own folder. Increases organization, and everything will be available under SimPEG.utils

NOTE: if you add a new function (or file), you must register it in __init__.py for it to be available under:

e.g.
...
from utils import mkvc, …
...
from MYNEWFILE import MYNEWFUNCTION

SimPEG/utils/sputils.py

@@ -0,0 +1,22 @@
+from scipy import sparse as sp
+from utils import mkvc
+
+
+def sdiag(h):
+    """Sparse diagonal matrix"""
+    return sp.spdiags(mkvc(h), 0, h.size, h.size, format="csr")
+
+
+def speye(n):
+    """Sparse identity"""
+    return sp.identity(n, format="csr")
+
+
+def kron3(A, B, C):
+    """Three kron prods"""
+    return sp.kron(sp.kron(A, B), C, format="csr")
+
+
+def spzeros(n1, n2):
+    """spzeros"""
+    return sp.coo_matrix((n1, n2)).tocsr()