Logic

Sometimes, it is necessary to apply multiple convergers.

The Logic family provides some logical combinations of convergers so that it is convenient to chain arbitrary number of convergers together.

Syntax

converger LogicAND (1) (2) (3)
converger LogicOR (1) (2) (3)
converger LogicXOR (1) (2) (3)
# (1) int, unique converger tag
# (2) int, tag of first converger in logical operation
# (3) int, tag of second converger in logical operation

Example

Let's assume, by default, the relative increment of displacement RelIncreDisp converger is preferred. However, when performing a response history analysis, when the first displacement increment of some substep is close to zero, then a small relative increment of displacement is not achievable due to machine precision. In this case, we want to add another converger using absolute increment of displacement AbsIncreDisp converger so that when absolute increment displacement is small enough, the analysis is continued.

It is possible to use LogicOR to achieve this.

converger RelIncreDisp 1 1E-10 10 true
converger AbsIncreDisp 2 1E-10 10 true
converger LogicOR 3 1 2

Note the last defined converger in any step will be used for that particular step. In this case, converger 3 using LogicOR would be used.

The following definition does not work.

converger LogicOR 3 1 2
converger RelIncreDisp 1 1E-10 10 true
converger AbsIncreDisp 2 1E-10 10 true

The chained convergers would be initialised recursively. This means it is possible to chain arbitrary number of convergers together. For example,

converger RelIncreDisp 1 1E-10 10 true
converger AbsIncreDisp 2 1E-10 10 true
converger LogicOR 3 1 2
converger AbsResidual 4 1E-10 10 true
converger LogicAND 5 3 4

Eventually, the converger 5 will be used, in which convergers 1, 2 and 4 will be called in order.