> For the complete documentation index, see [llms.txt](https://tlcfem.gitbook.io/suanpan-manual/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://tlcfem.gitbook.io/suanpan-manual/converger/other/logic.md).

# 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`](/suanpan-manual/converger/relative/relincredisp.md) 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`](/suanpan-manual/converger/absolute/absincredisp.md) 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.


---

# Agent Instructions
This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com.

## Querying This Documentation
If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://tlcfem.gitbook.io/suanpan-manual/converger/other/logic.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.