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//! Create cycles in a timely dataflow graph.
use crate::Data;
use crate::progress::{Timestamp, PathSummary};
use crate::progress::frontier::Antichain;
use crate::order::Product;
use crate::dataflow::channels::pushers::Tee;
use crate::dataflow::channels::pact::Pipeline;
use crate::dataflow::{Stream, Scope};
use crate::dataflow::scopes::child::Iterative;
use crate::dataflow::operators::generic::builder_rc::OperatorBuilder;
use crate::dataflow::operators::generic::OutputWrapper;
/// Creates a `Stream` and a `Handle` to later bind the source of that `Stream`.
pub trait Feedback<G: Scope> {
/// Creates a `Stream` and a `Handle` to later bind the source of that `Stream`.
///
/// The resulting `Stream` will have its data defined by a future call to `connect_loop` with
/// its `Handle` passed as an argument. Data passed through the stream will have their
/// timestamps advanced by `summary`, and will be dropped if the result exceeds `limit`.
///
/// # Examples
/// ```
/// use timely::dataflow::Scope;
/// use timely::dataflow::operators::{Feedback, ConnectLoop, ToStream, Concat, Inspect, BranchWhen};
///
/// timely::example(|scope| {
/// // circulate 0..10 for 100 iterations.
/// let (handle, cycle) = scope.feedback(1);
/// (0..10).to_stream(scope)
/// .concat(&cycle)
/// .inspect(|x| println!("seen: {:?}", x))
/// .branch_when(|t| t < &100).1
/// .connect_loop(handle);
/// });
/// ```
fn feedback<D: Data>(&mut self, summary: <G::Timestamp as Timestamp>::Summary) -> (Handle<G, D>, Stream<G, D>);
}
/// Creates a `Stream` and a `Handle` to later bind the source of that `Stream`.
pub trait LoopVariable<'a, G: Scope, T: Timestamp> {
/// Creates a `Stream` and a `Handle` to later bind the source of that `Stream`.
///
/// The resulting `Stream` will have its data defined by a future call to `connect_loop` with
/// its `Handle` passed as an argument. Data passed through the stream will have their
/// timestamps advanced by `summary`, and will be dropped if the result exceeds `limit`.
///
/// # Examples
/// ```
/// use timely::dataflow::Scope;
/// use timely::dataflow::operators::{LoopVariable, ConnectLoop, ToStream, Concat, Inspect, BranchWhen};
///
/// timely::example(|scope| {
/// // circulate 0..10 for 100 iterations.
/// scope.iterative::<usize,_,_>(|inner| {
/// let (handle, cycle) = inner.loop_variable(1);
/// (0..10).to_stream(inner)
/// .concat(&cycle)
/// .inspect(|x| println!("seen: {:?}", x))
/// .branch_when(|t| t.inner < 100).1
/// .connect_loop(handle);
/// });
/// });
/// ```
fn loop_variable<D: Data>(&mut self, summary: T::Summary) -> (Handle<Iterative<'a, G, T>, D>, Stream<Iterative<'a, G, T>, D>);
}
impl<G: Scope> Feedback<G> for G {
fn feedback<D: Data>(&mut self, summary: <G::Timestamp as Timestamp>::Summary) -> (Handle<G, D>, Stream<G, D>) {
let mut builder = OperatorBuilder::new("Feedback".to_owned(), self.clone());
let (output, stream) = builder.new_output();
(Handle { builder, summary, output }, stream)
}
}
impl<'a, G: Scope, T: Timestamp> LoopVariable<'a, G, T> for Iterative<'a, G, T> {
fn loop_variable<D: Data>(&mut self, summary: T::Summary) -> (Handle<Iterative<'a, G, T>, D>, Stream<Iterative<'a, G, T>, D>) {
self.feedback(Product::new(Default::default(), summary))
}
}
/// Connect a `Stream` to the input of a loop variable.
pub trait ConnectLoop<G: Scope, D: Data> {
/// Connect a `Stream` to be the input of a loop variable.
///
/// # Examples
/// ```
/// use timely::dataflow::Scope;
/// use timely::dataflow::operators::{Feedback, ConnectLoop, ToStream, Concat, Inspect, BranchWhen};
///
/// timely::example(|scope| {
/// // circulate 0..10 for 100 iterations.
/// let (handle, cycle) = scope.feedback(1);
/// (0..10).to_stream(scope)
/// .concat(&cycle)
/// .inspect(|x| println!("seen: {:?}", x))
/// .branch_when(|t| t < &100).1
/// .connect_loop(handle);
/// });
/// ```
fn connect_loop(&self, _: Handle<G, D>);
}
impl<G: Scope, D: Data> ConnectLoop<G, D> for Stream<G, D> {
fn connect_loop(&self, helper: Handle<G, D>) {
let mut builder = helper.builder;
let summary = helper.summary;
let mut output = helper.output;
let mut input = builder.new_input_connection(self, Pipeline, vec![Antichain::from_elem(summary.clone())]);
let mut vector = Vec::new();
builder.build(move |_capability| move |_frontier| {
let mut output = output.activate();
input.for_each(|cap, data| {
data.swap(&mut vector);
if let Some(new_time) = summary.results_in(cap.time()) {
let new_cap = cap.delayed(&new_time);
output
.session(&new_cap)
.give_vec(&mut vector);
}
});
});
}
}
/// A handle used to bind the source of a loop variable.
pub struct Handle<G: Scope, D: Data> {
builder: OperatorBuilder<G>,
summary: <G::Timestamp as Timestamp>::Summary,
output: OutputWrapper<G::Timestamp, D, Tee<G::Timestamp, D>>,
}