# dvcompute_gpss_branch

This crate is a part of discrete event simulation framework DVCompute Simulator (registration
number 2021660590 of Rospatent). The `dvcompute_gpss_branch` crate defines a GPSS-like DSL for
nested simulation, but the same code base is shared by the `dvcompute_gpss_dist` crate
destined for optimistic distributed simulation.

The DSL language implements analogs of the following blocks: PREEMPT, RETURN, ASSEMBLE, GATHER,
SPLIT, TRANSFER and others. The SELECT block is naturally expressed as a composition of computations.
There are analogs of the facility and storage entities.

There are the following main crates: `dvcompute` (sequential simulation),
`dvcompute_dist` (optimistic distributed simulation),
`dvcompute_cons` (conservative distributed simulation) and
`dvcompute_branch` (nested simulation). All four crates are
very close. They are based on the same method.

## Simulation Method

Here is an example, where each student arrival is modeled by some transact. These transacts
are processed by the block computations:

```rust
fn student_chain(line: Grc<Queue>, prof: Grc<Facility<f64>>) -> BlockBox<Transact<f64>, ()> {
    queue_block(line.clone(), 1)
        .and_then(seize_block(prof.clone()))
        .and_then(depart_block(line.clone(), 1))
        .and_then({
            advance_block(random_exponential_process_(1000.0))
        })
        .and_then(let_go_chain(line, prof))
        .into_boxed()
}

fn let_go_chain(_line: Grc<Queue>, prof: Grc<Facility<f64>>) -> BlockBox<Transact<f64>, ()> {
    release_block(prof)
        .and_then(terminate_block())
        .into_boxed()
}
```

These computations are arrows in terms of functional programming. They are combined with help of 
composition. Such computations should be run later to take effect.

## Examples

You can find examples in the author's [repository](https://gitflic.ru/project/dsorokin/dvcompute).

## Documentation

* [API docs](https://docs.rs/dvcompute_gpss_branch/)

## Bibliography

* Sorokin David. DVCompute Simulator for discrete event simulation.
  Prikladnaya informatika=Journal of Applied Informatics, 2021, vol.16, no.3, pp.93-108 (in Russian).
  DOI: 10.37791/2687-0649-2021-16-3-93-108

## Licence

Copyright 2020-2024 David Sorokin <davsor@mail.ru>, based in Yoshkar-Ola, Russia

This software is subject to the terms of the Mozilla Public
License, v. 2.0. If a copy of the MPL was not distributed with this
file, You can obtain one at <http://mozilla.org/MPL/2.0/>.