First version of new submodule roots

pyerrors/__init__.py

@@ -4,3 +4,4 @@ from . import linalg
 from . import misc
 from . import mpm
 from . import correlators
+from . import roots

pyerrors/roots.py

@@ -0,0 +1,23 @@
+#!/usr/bin/env python
+# coding: utf-8
+
+import scipy.optimize
+from autograd import jacobian
+from .pyerrors import Obs, derived_observable, pseudo_Obs
+
+def find_root(d, func, guess=1.0, **kwargs):
+    """Finds the root of the function func(x, d) where d is an Obs.
+
+    Parameters
+    -----------------
+    d -- Obs passed to the function.
+    func -- Function to be minimized.
+    guess -- Initial guess for the minimization.
+    """
+    root = scipy.optimize.fsolve(func, guess, d.value)
+
+    dx = jacobian(func)(root[0], d.value)
+    da = jacobian(lambda u, v : func(v, u))(d.value, root[0])
+    deriv = - da / dx
+
+    return derived_observable(lambda x, **kwargs: x[0], [pseudo_Obs(root, 0.0, d.names[0], d.shape[d.names[0]]), d], man_grad=[0, deriv])