Easier generation of description dictionaries

pySDC/core/Level.py

@@ -14,7 +14,7 @@ def __init__(self, params):
         # freeze class, no further attributes allowed from this point
         self._freeze()
 
-        self.dt_initial = self.dt * 1.0
+        self.dt_initial = self.dt * 1.0 if self.dt is not None else None
 
 
 # short helper class to bundle all status variables

pySDC/core/Problem.py

@@ -73,6 +73,10 @@ def f_init(self):
         """Generate a data variable for RHS"""
         return self.dtype_f(self.init)
 
+    @classmethod
+    def get_default_sweeper_class(cls):
+        raise NotImplementedError(f'No default sweeper class implemented for {cls} problem!')
+
     def eval_f(self, u, t):
         """
         Abstract interface to RHS computation of the ODE

pySDC/helpers/setup_helper.py

@@ -0,0 +1,45 @@
+def generate_description(problem_class, **kwargs):
+    """
+    Generate a description object that you can use to run pySDC based on a problem class and various input.
+    This function does not set any additional defaults, but distributes the values to where they belong.
+
+    Args:
+        problem_class (pySDC.Problem): A problem class
+
+    Returns:
+        dict: A description object for running pySDC
+    """
+    from pySDC.core.Level import _Pars as level_params
+    from pySDC.core.Step import _Pars as step_params
+
+    description = {
+        'level_params': {},
+        'problem_params': {},
+        'sweeper_params': {},
+        'problem_class': problem_class,
+        'step_params': {},
+        'sweeper_class': kwargs.get('sweeper_class', problem_class.get_default_sweeper_class()),
+        'convergence_controllers': {},
+    }
+
+    problem_keys = problem_class.__init__.__code__.co_varnames
+    level_keys = level_params({}).__dict__.keys()
+    sweeper_keys = description['sweeper_class']({'num_nodes': 1, 'quad_type': 'RADAU-RIGHT'}).params.__dict__.keys()
+    step_keys = step_params({}).__dict__.keys()
+
+    # TODO: add convergence controllers
+    for key, val in kwargs.items():
+        if key in problem_keys:
+            description['problem_params'][key] = val
+        elif key in level_keys:
+            description['level_params'][key] = val
+        elif key in sweeper_keys:
+            description['sweeper_params'][key] = val
+        elif key in step_keys:
+            description['step_params'][key] = val
+        elif key == 'sweeper_class':
+            pass
+        else:
+            raise ValueError(f'Don\'t know what parameter \"{key}\" is for!')
+
+    return description

pySDC/implementations/problem_classes/generic_ND_FD.py

@@ -167,6 +167,12 @@ def grids(self):
         if self.ndim == 3:
             return x[None, :, None], x[:, None, None], x[None, None, :]
 
+    @classmethod
+    def get_default_sweeper_class(cls):
+        from pySDC.implementations.sweeper_classes.generic_implicit import generic_implicit
+
+        return generic_implicit
+
     def eval_f(self, u, t):
         """
         Routine to evaluate the right-hand side of the problem.

pySDC/tests/test_helpers/test_setup_helper.py

@@ -0,0 +1,59 @@
+import pytest
+
+
+@pytest.mark.base
+def test_setup_helper():
+    from pySDC.helpers.setup_helper import generate_description
+    from pySDC.implementations.problem_classes.AdvectionEquation_ND_FD import advectionNd
+    from pySDC.implementations.sweeper_classes.generic_implicit import generic_implicit
+
+    # build classic description
+    # initialize level parameters
+    level_params = {}
+    level_params['dt'] = 0.05
+
+    # initialize sweeper parameters
+    sweeper_params = {}
+    sweeper_params['quad_type'] = 'RADAU-RIGHT'
+    sweeper_params['num_nodes'] = 3
+    sweeper_params['QI'] = 'IE'
+
+    problem_params = {'freq': 2, 'nvars': 2**9, 'c': 1.0, 'stencil_type': 'center', 'order': 4, 'bc': 'periodic'}
+
+    # initialize step parameters
+    step_params = {}
+    step_params['maxiter'] = 5
+
+    description = {}
+    description['problem_class'] = advectionNd
+    description['problem_params'] = problem_params
+    description['sweeper_class'] = generic_implicit
+    description['sweeper_params'] = sweeper_params
+    description['level_params'] = level_params
+    description['step_params'] = step_params
+    description['convergence_controllers'] = {}
+
+    easy_description = generate_description(
+        problem_class=advectionNd, **problem_params, **level_params, **sweeper_params, **step_params
+    )
+
+    assert (
+        easy_description == description
+    ), 'The generate description function did not reproduce the desired description'
+
+    easy_description = generate_description(
+        problem_class=advectionNd,
+        sweeper_class=generic_implicit,
+        **problem_params,
+        **level_params,
+        **sweeper_params,
+        **step_params
+    )
+
+    assert (
+        easy_description == description
+    ), 'The generate description function did not reproduce the desired description when supplying a sweeper class'
+
+
+if __name__ == '__main__':
+    test_setup_helper()