3.1.1.5. c3po.couplers.FixedPointCoupler module

Contain the class FixedPointCoupler.

class c3po.couplers.FixedPointCoupler.FixedPointCoupler(physics, exchangers, dataManagers)

Bases: Coupler

FixedPointCoupler inherits from Coupler and proposes a damped fixed point algorithm.

The class proposes an algorithm for the resolution of \(F(X) = X\). Thus FixedPointCoupler is a Coupler working with :

A single PhysicsDriver (possibly a Coupler) defining the calculations to be made each time \(F\) is called.
A list of DataManager allowing to manipulate the data in the coupling (the \(X\)).
Two Exchanger allowing to go from the PhysicsDriver to the DataManager and vice versa.

Each DataManager is normalized with its own norm got after the first iteration. They are then used as a single DataManager using CollaborativeDataManager.

At each iteration we do (with \(n\) the iteration number and alpha the damping factor):

\[X^{n+1} = \alpha . F(X^{n}) + (1 - \alpha).X^{n}\]

The convergence criteria is : \(||F(X^{n}) - X^{n}|| / ||F(X^{n})|| < \rm{tolerance}\). The default norm used is the infinite norm. setNormChoice() allows to choose another one.

The default value of tolerance is 1.E-6. Call setConvergenceParameters() to change it.

The default maximum number of iterations is 100. Call setConvergenceParameters() to change it.

The default damping factor is 1 (no damping). Call setDampingFactor() to change it.

__init__(physics, exchangers, dataManagers)

Build a FixedPointCoupler object.

Parameters:

physics (list[PhysicsDriver]) – List of only one PhysicsDriver (possibly a Coupler).
exchangers (list[Exchanger]) – List of exactly two Exchanger allowing to go from the PhysicsDriver to the DataManager and vice versa.
dataManagers (list[DataManager]) – List of DataManager.

getIterateStatus(): See PhysicsDriver.getSolveStatus().

getSolveStatus(): See PhysicsDriver.getSolveStatus().

initTimeStep(dt): See c3po.PhysicsDriver.PhysicsDriver.initTimeStep().

iterateTimeStep()

Make on iteration of a damped fixed-point algorithm.

setConvergenceParameters(tolerance, maxiter)

Set the convergence parameters (tolerance and maximum number of iterations).

Parameters:

tolerance – The convergence threshold in \(||F(X^{n}) - X^{n}|| / ||F(X^{n})|| < \rm{tolerance}\).
maxiter – The maximal number of iterations.

setDampingFactor(dampingFactor)

Set the damping factor of the method.

Parameters:: dampingFactor – The damping factor alpha in the formula \(X^{n+1} = \alpha . F(X^{n}) + (1 - \alpha).X^{n}\).

setFailureManagement(leaveIfSolvingFailed)

Set if iterations should continue or not in case of solver failure (solveTimeStep() returns False).

Parameters:: leaveIfSolvingFailed (bool) – Set False to continue the iterations, True to stop. Default: False.

setPrintLevel(level)

Set the print level during iterations (0=None, 1 keeps last iteration, 2 prints every iteration).

Parameters:: level (int) – Integer in range [0;2]. Default: 2.

setUseIterate(useIterate)

If True is given, the iterate() method on the given PhysicsDriver is called instead of the solve() method.

Parameters:: useIterate (bool) – Set True to use iterate(), False to use solve(). Default: False.

solveTimeStep()

Solve a time step using the damped fixed-point algorithm.