Merge 7c2082a into c85ac17

openmdao/docs/feature_reference/building_blocks/solvers/linear/linear_user_defined.rst

@@ -9,6 +9,30 @@ This is a solver that let's you define custom method for performing a linear sol
 method is named "solve_linear", but you can give it any name by passing in the function or method handle to
 the "solve_function" attribute.
 
+The function needs to have the following signature:
+
+.. code-block:: python
+
+    def my_solve_function(d_outputs, d_residuals, mode):
+        r"""
+        Apply inverse jac product. The model is assumed to be in an unscaled state.
+
+        Parameters
+        ----------
+        d_outputs : Vector
+            unscaled, dimensional quantities read via d_outputs[key]
+        d_residuals : Vector
+            unscaled, dimensional quantities read via d_residuals[key]
+        mode : str
+            either 'fwd' or 'rev'
+
+        Returns
+        -------
+        None or bool or (bool, float, float)
+            The bool is the failure flag; and the two floats are absolute and relative error.
+        """
+
+
 Here is a rather contrived example where an identity preconditioner is used by giving the component's "mysolve"
 method to a LinearUserDefined solver.
 

openmdao/solvers/linear/user_defined.py

@@ -20,7 +20,8 @@ def __init__(self, solve_function=None, **kwargs):
         Parameters
         ----------
         solve_function : function
-            Custom function containing the solve_linear function.
+            Custom function containing the solve_linear function. The default is None, which means
+            the name defaults to "solve_linear".
         **kwargs : dict
             Options dictionary.
         """