feat(fode): more robust time span handling

alexfikl · Oct 2, 2023 · ced7271 · ced7271
1 parent 7c2e85c
commit ced7271
Show file tree

Hide file tree

Showing 11 changed files with 295 additions and 152 deletions.
diff --git a/docs/changelog.rst b/docs/changelog.rst
@@ -13,8 +13,6 @@ Features
 ^^^^^^^^
 
 * Added an example with the fractional Lorenz system (:ghpr:`13`).
-* Support setting a constant for
-  :meth:`~pycaputo.fode.FractionalDifferentialEquationMethod.predict_time_step`.
 * Add a guess for the number of corrector iterations
   for :class:`~pycaputo.fode.CaputoPECEMethod` from [Garrappa2010]_.
 * Implement :class:`~pycaputo.quadrature.RiemannLiouvilleSimpsonMethod`, a

diff --git a/docs/fode.rst b/docs/fode.rst
@@ -17,23 +17,34 @@ History Handling
 .. autoclass:: FixedState
 .. autoclass:: FixedSizeHistory
 
-Interface
----------
+Time Interval Handling
+----------------------
+
+.. exception:: StepEstimateError
+
+.. autoclass:: TimeSpan
+.. autoclass:: FixedTimeSpan
+.. autoclass:: GradedTimeSpan
+.. autoclass:: FixedLipschitzTimeSpan
+.. autoclass:: LipschitzTimeSpan
+
+Time Stepping Events
+--------------------
 
 .. autoclass:: Event
 .. autoclass:: StepFailed
 .. autoclass:: StepCompleted
 
+Time Stepping Interface
+-----------------------
+
 .. autoclass:: FractionalDifferentialEquationMethod
 .. autoclass:: ProductIntegrationMethod
 
 .. autofunction:: evolve
 .. autofunction:: advance
 .. autofunction:: make_initial_condition
 
-.. autofunction:: make_predict_time_step_fixed
-.. autofunction:: make_predict_time_step_graded
-
 Caputo Derivative FODEs
 =======================
 

diff --git a/docs/references.rst b/docs/references.rst
@@ -31,6 +31,10 @@ References
     International Journal of Computer Mathematics, Vol. 87, pp. 2281--2290, 2010,
     `DOI <https://doi.org/10.1080/00207160802624331>`__.
 
+.. [Baleanu2012] D. Baleanu, K. Diethelm, E. Scalas, J. J. Trujillo,
+    *Fractional Calculus - Models and Numerical Methods*,
+    World Scientific, 2012.
+
 .. [Garrappa2015] R. Garrappa,
     *Numerical Evaluation of Two and Three Parameter Mittag-Leffler Functions*,
     SIAM Journal on Numerical Analysis, Vol. 53, pp. 1350--1369, 2015,

diff --git a/examples/brusselator-predictor-corrector.py b/examples/brusselator-predictor-corrector.py
@@ -24,7 +24,7 @@ def brusselator(t: float, y: Array, *, a: float, mu: float) -> Array:
 
 # {{{ solve
 
-from pycaputo.fode import CaputoPECEMethod
+from pycaputo.fode import CaputoPECEMethod, FixedTimeSpan
 
 alpha = 0.8
 a = 1.0
@@ -33,9 +33,8 @@ def brusselator(t: float, y: Array, *, a: float, mu: float) -> Array:
 
 stepper = CaputoPECEMethod(
     derivative_order=(alpha,),
-    predict_time_step=1.0e-2,
+    tspan=FixedTimeSpan.from_data(1.0e-2, tstart=0.0, tfinal=50.0),
     source=partial(brusselator, a=a, mu=mu),
-    tspan=(0, 50),
     y0=(y0,),
     corrector_iterations=1,
 )

diff --git a/examples/fractional-lorenz.py b/examples/fractional-lorenz.py
@@ -36,7 +36,7 @@ def lorenz_jac(t: float, y: Array, *, sigma: float, rho: float, beta: float) ->
 
 # {{{ solve
 
-from pycaputo.fode import CaputoWeightedEulerMethod
+from pycaputo.fode import CaputoWeightedEulerMethod, FixedTimeSpan
 
 # NOTE: order example taken from https://doi.org/10.1016/j.chaos.2009.03.016
 alpha = (0.985, 0.99, 0.99)
@@ -49,10 +49,9 @@ def lorenz_jac(t: float, y: Array, *, sigma: float, rho: float, beta: float) ->
 
 stepper = CaputoWeightedEulerMethod(
     derivative_order=alpha,
-    predict_time_step=1.0e-2,
+    tspan=FixedTimeSpan.from_data(1.0e-2, tstart=0.0, tfinal=75.0),
     source=partial(lorenz, sigma=sigma, rho=rho, beta=beta),
     source_jac=partial(lorenz_jac, sigma=sigma, rho=rho, beta=beta),
-    tspan=(0, 75),
     y0=(y0,),
     theta=1.0,
 )

diff --git a/pycaputo/fode/__init__.py b/pycaputo/fode/__init__.py
@@ -3,14 +3,18 @@
 
 from pycaputo.fode.base import (
     Event,
+    FixedLipschitzTimeSpan,
+    FixedTimeSpan,
     FractionalDifferentialEquationMethod,
+    GradedTimeSpan,
+    LipschitzTimeSpan,
     StepCompleted,
+    StepEstimateError,
     StepFailed,
+    TimeSpan,
     advance,
     evolve,
     make_initial_condition,
-    make_predict_time_step_fixed,
-    make_predict_time_step_graded,
 )
 from pycaputo.fode.caputo import (
     CaputoForwardEulerMethod,
@@ -47,6 +51,12 @@
     "FixedState",
     "FractionalDifferentialEquationMethod",
     "History",
+    "StepEstimateError",
+    "TimeSpan",
+    "FixedTimeSpan",
+    "FixedLipschitzTimeSpan",
+    "GradedTimeSpan",
+    "LipschitzTimeSpan",
     "ProductIntegrationMethod",
     "ProductIntegrationState",
     "State",
@@ -56,6 +66,4 @@
     "advance",
     "evolve",
     "make_initial_condition",
-    "make_predict_time_step_fixed",
-    "make_predict_time_step_graded",
 )