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//! Count the number of occurrences of each element.
use timely::dataflow::channels::pact::Pipeline;
use timely::dataflow::operators::Operator;
use timely::dataflow::*;
use timely::order::TotalOrder;
use crate::collection::AsCollection;
use crate::difference::{IsZero, Semigroup};
use crate::hashable::Hashable;
use crate::lattice::Lattice;
use crate::operators::arrange::{ArrangeBySelf, Arranged};
use crate::trace::{BatchReader, Cursor, TraceReader};
use crate::{ExchangeData, VecCollection};
/// Extension trait for the `count` differential dataflow method.
pub trait CountTotal<G: Scope<Timestamp: TotalOrder + Lattice + Ord>, K: ExchangeData, R: Semigroup>
{
/// Counts the number of occurrences of each element.
///
/// # Examples
///
/// ```
/// use palimpsest_dataflow::input::Input;
/// use palimpsest_dataflow::operators::CountTotal;
///
/// ::timely::example(|scope| {
/// // report the number of occurrences of each key
/// scope.new_collection_from(1 .. 10).1
/// .map(|x| x / 3)
/// .count_total();
/// });
/// ```
fn count_total(&self) -> VecCollection<G, (K, R), isize> {
self.count_total_core()
}
/// Count for general integer differences.
///
/// This method allows `count_total` to produce collections whose difference
/// type is something other than an `isize` integer, for example perhaps an
/// `i32`.
fn count_total_core<R2: Semigroup + From<i8> + 'static>(&self) -> VecCollection<G, (K, R), R2>;
}
impl<G, K: ExchangeData + Hashable, R: ExchangeData + Semigroup> CountTotal<G, K, R>
for VecCollection<G, K, R>
where
G: Scope<Timestamp: TotalOrder + Lattice + Ord>,
{
fn count_total_core<R2: Semigroup + From<i8> + 'static>(&self) -> VecCollection<G, (K, R), R2> {
self.arrange_by_self_named("Arrange: CountTotal")
.count_total_core()
}
}
impl<G, K, T1> CountTotal<G, K, T1::Diff> for Arranged<G, T1>
where
G: Scope<Timestamp = T1::Time>,
T1: for<'a> TraceReader<
Key<'a> = &'a K,
Val<'a> = &'a (),
Time: TotalOrder,
Diff: ExchangeData + Semigroup<T1::DiffGat<'a>>,
> + Clone
+ 'static,
K: ExchangeData,
{
fn count_total_core<R2: Semigroup + From<i8> + 'static>(
&self,
) -> VecCollection<G, (K, T1::Diff), R2> {
let mut trace = self.trace.clone();
self.stream
.unary_frontier(Pipeline, "CountTotal", move |_, _| {
// tracks the lower and upper limit of received batches.
let mut lower_limit = timely::progress::frontier::Antichain::from_elem(
<G::Timestamp as timely::progress::Timestamp>::minimum(),
);
let mut upper_limit = timely::progress::frontier::Antichain::from_elem(
<G::Timestamp as timely::progress::Timestamp>::minimum(),
);
move |(input, _frontier), output| {
let mut batch_cursors = Vec::new();
let mut batch_storage = Vec::new();
// Downgrade previous upper limit to be current lower limit.
lower_limit.clear();
lower_limit.extend(upper_limit.borrow().iter().cloned());
let mut cap = None;
input.for_each(|capability, batches| {
if cap.is_none() {
// NB: Assumes batches are in-order
cap = Some(capability.retain());
}
for batch in batches.drain(..) {
upper_limit.clone_from(batch.upper()); // NB: Assumes batches are in-order
batch_cursors.push(batch.cursor());
batch_storage.push(batch);
}
});
if let Some(capability) = cap {
let mut session = output.session(&capability);
use crate::trace::cursor::CursorList;
let mut batch_cursor = CursorList::new(batch_cursors, &batch_storage);
let (mut trace_cursor, trace_storage) =
trace.cursor_through(lower_limit.borrow()).unwrap();
while let Some(key) = batch_cursor.get_key(&batch_storage) {
let mut count: Option<T1::Diff> = None;
trace_cursor.seek_key(&trace_storage, key);
if trace_cursor.get_key(&trace_storage) == Some(key) {
trace_cursor.map_times(&trace_storage, |_, diff| {
count.as_mut().map(|c| c.plus_equals(&diff));
if count.is_none() {
count = Some(T1::owned_diff(diff));
}
});
}
batch_cursor.map_times(&batch_storage, |time, diff| {
if let Some(count) = count.as_ref() {
if !count.is_zero() {
session.give((
(key.clone(), count.clone()),
T1::owned_time(time),
R2::from(-1i8),
));
}
}
count.as_mut().map(|c| c.plus_equals(&diff));
if count.is_none() {
count = Some(T1::owned_diff(diff));
}
if let Some(count) = count.as_ref() {
if !count.is_zero() {
session.give((
(key.clone(), count.clone()),
T1::owned_time(time),
R2::from(1i8),
));
}
}
});
batch_cursor.step_key(&batch_storage);
}
}
// tidy up the shared input trace.
trace.advance_upper(&mut upper_limit);
trace.set_logical_compaction(upper_limit.borrow());
trace.set_physical_compaction(upper_limit.borrow());
}
})
.as_collection()
}
}