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//! Create cycles in a timely dataflow graph.
use crate::Container;
use crate::dataflow::channels::pact::Pipeline;
use crate::dataflow::operators::generic::builder_rc::OperatorBuilder;
use crate::dataflow::scope::Iterative;
use crate::dataflow::{Stream, Scope};
use crate::order::Product;
use crate::progress::frontier::Antichain;
use crate::progress::{Timestamp, PathSummary};
/// Creates a `Stream` and a `Handle` to later bind the source of that `Stream`.
pub trait Feedback<'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. Containers passed through the stream will have their
/// timestamps advanced by `summary`.
///
/// # Examples
/// ```
/// use timely::dataflow::Scope;
/// use timely::dataflow::operators::{Feedback, ConnectLoop, ToStream, Concat, Inspect};
/// use timely::dataflow::operators::vec::BranchWhen;
///
/// timely::example(|scope| {
/// // circulate 0..10 for 100 iterations.
/// let (handle, cycle) = scope.feedback(1);
/// (0..10).to_stream(scope)
/// .container::<Vec<_>>()
/// .concat(cycle)
/// .inspect(|x| println!("seen: {:?}", x))
/// .branch_when(|t| t < &100).1
/// .connect_loop(handle);
/// });
/// ```
fn feedback<C: Container>(&self, summary: <T as Timestamp>::Summary) -> (Handle<'scope, T, C>, Stream<'scope, T, C>);
}
/// Creates a `Stream` and a `Handle` to later bind the source of that `Stream`.
pub trait LoopVariable<'scope, TOuter: Timestamp, TInner: 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. Containers passed through the stream will have their
/// timestamps advanced by `summary`.
///
/// # Examples
/// ```
/// use timely::dataflow::Scope;
/// use timely::dataflow::operators::{LoopVariable, ConnectLoop, ToStream, Concat, Inspect};
/// use timely::dataflow::operators::vec::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)
/// .container::<Vec<_>>()
/// .concat(cycle)
/// .inspect(|x| println!("seen: {:?}", x))
/// .branch_when(|t| t.inner < 100).1
/// .connect_loop(handle);
/// });
/// });
/// ```
fn loop_variable<C: Container>(&self, summary: TInner::Summary) -> (Handle<'scope, Product<TOuter, TInner>, C>, Stream<'scope, Product<TOuter, TInner>, C>);
}
impl<'scope, T: Timestamp> Feedback<'scope, T> for Scope<'scope, T> {
fn feedback<C: Container>(&self, summary: <T as Timestamp>::Summary) -> (Handle<'scope, T, C>, Stream<'scope, T, C>) {
let mut builder = OperatorBuilder::new("Feedback".to_owned(), *self);
let (output, stream) = builder.new_output();
(Handle { builder, summary, output }, stream)
}
}
impl<'scope, TOuter: Timestamp, TInner: Timestamp> LoopVariable<'scope, TOuter, TInner> for Iterative<'scope, TOuter, TInner> {
fn loop_variable<C: Container>(&self, summary: TInner::Summary) -> (Handle<'scope, Product<TOuter, TInner>, C>, Stream<'scope, Product<TOuter, TInner>, C>) {
self.feedback(Product::new(Default::default(), summary))
}
}
/// Connect a `Stream` to the input of a loop variable.
pub trait ConnectLoop<'scope, T: Timestamp, C: Container> {
/// 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};
/// use timely::dataflow::operators::vec::BranchWhen;
///
/// timely::example(|scope| {
/// // circulate 0..10 for 100 iterations.
/// let (handle, cycle) = scope.feedback(1);
/// (0..10).to_stream(scope)
/// .container::<Vec<_>>()
/// .concat(cycle)
/// .inspect(|x| println!("seen: {:?}", x))
/// .branch_when(|t| t < &100).1
/// .connect_loop(handle);
/// });
/// ```
fn connect_loop(self, handle: Handle<'scope, T, C>);
}
impl<'scope, T: Timestamp, C: Container> ConnectLoop<'scope, T, C> for Stream<'scope, T, C> {
fn connect_loop(self, handle: Handle<'scope, T, C>) {
let mut builder = handle.builder;
let summary = handle.summary;
let mut output = handle.output;
let mut input = builder.new_input_connection(self, Pipeline, [(0, Antichain::from_elem(summary.clone()))]);
builder.set_notify_for(0, crate::progress::operate::FrontierInterest::Never);
builder.build(move |_capability| move |_frontier| {
let mut output = output.activate();
input.for_each(|cap, data| {
if let Some(new_time) = summary.results_in(cap.time()) {
let new_cap = cap.delayed(&new_time, output.output_index());
output.give(&new_cap, data);
}
});
});
}
}
/// A handle used to bind the source of a loop variable.
#[derive(Debug)]
pub struct Handle<'scope, T: Timestamp, C: Container> {
builder: OperatorBuilder<'scope, T>,
summary: <T as Timestamp>::Summary,
output: crate::dataflow::channels::pushers::Output<T, C>,
}