[−][src]Struct timely::progress::change_batch::ChangeBatch
A collection of updates of the form (T, i64)
.
A ChangeBatch
accumulates updates of the form (T, i64)
, where it is capable of consolidating
the representation and removing elements whose i64
field accumulates to zero.
The implementation is designed to be as lazy as possible, simply appending to a list of updates until they are required. This means that several seemingly simple operations may be expensive, in that they may provoke a compaction. I've tried to prevent exposing methods that allow surprisingly expensive operations; all operations should take an amortized constant or logarithmic time.
Methods
impl<T: Ord> ChangeBatch<T>
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pub fn new() -> ChangeBatch<T>
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Allocates a new empty ChangeBatch
.
Examples
use timely::progress::ChangeBatch; let mut batch = ChangeBatch::<usize>::new(); assert!(batch.is_empty());
pub fn new_from(key: T, val: i64) -> ChangeBatch<T>
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Allocates a new ChangeBatch
with a single entry.
Examples
use timely::progress::ChangeBatch; let mut batch = ChangeBatch::<usize>::new_from(17, 1); assert!(!batch.is_empty());
pub fn is_dirty(&self) -> bool
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Returns true if the change batch is not guaranteed compact.
pub fn update(&mut self, item: T, value: i64)
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Adds a new update, for item
with value
.
This could be optimized to perform compaction when the number of "dirty" elements exceeds half the length of the list, which would keep the total footprint within reasonable bounds even under an arbitrary number of updates. This has a cost, and it isn't clear whether it is worth paying without some experimentation.
Examples
use timely::progress::ChangeBatch; let mut batch = ChangeBatch::<usize>::new(); batch.update(17, 1); assert!(!batch.is_empty());
pub fn extend<I: Iterator<Item = (T, i64)>>(&mut self, iterator: I)
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Performs a sequence of updates described by iterator
.
Examples
use timely::progress::ChangeBatch; let mut batch = ChangeBatch::<usize>::new_from(17, 1); batch.extend(vec![(17, -1)].into_iter()); assert!(batch.is_empty());
pub fn into_inner(self) -> Vec<(T, i64)>
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Extracts the Vec<(T, i64)>
from the map, consuming it.
Examples
use timely::progress::ChangeBatch; let batch = ChangeBatch::<usize>::new_from(17, 1); assert_eq!(batch.into_inner(), vec![(17, 1)]);
pub fn iter(&mut self) -> Iter<(T, i64)>
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Iterates over the contents of the map.
Examples
use timely::progress::ChangeBatch; let mut batch = ChangeBatch::<usize>::new_from(17, 1); { // scope allows borrow of `batch` to drop. let mut iter = batch.iter(); assert_eq!(iter.next(), Some(&(17, 1))); assert_eq!(iter.next(), None); } assert!(!batch.is_empty());
pub fn drain(&mut self) -> Drain<(T, i64)>
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Drains the set of updates.
This operation first compacts the set of updates so that the drained results have at most one occurence of each item.
Examples
use timely::progress::ChangeBatch; let mut batch = ChangeBatch::<usize>::new_from(17, 1); { // scope allows borrow of `batch` to drop. let mut iter = batch.drain(); assert_eq!(iter.next(), Some((17, 1))); assert_eq!(iter.next(), None); } assert!(batch.is_empty());
pub fn clear(&mut self)
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Clears the map.
Examples
use timely::progress::ChangeBatch; let mut batch = ChangeBatch::<usize>::new_from(17, 1); batch.clear(); assert!(batch.is_empty());
pub fn is_empty(&mut self) -> bool
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True iff all keys have value zero.
This method requires mutable access to self
because it may need to compact the representation
to determine if the batch of updates is indeed empty. We could also implement a weaker form of
is_empty
which just checks the length of self.updates
, and which could confirm the absence of
any updates, but could report false negatives if there are updates which would cancel.
Examples
use timely::progress::ChangeBatch; let mut batch = ChangeBatch::<usize>::new_from(17, 1); batch.update(17, -1); assert!(batch.is_empty());
pub fn canonicalize(&mut self)
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please use compact
instead
Compact and sort data, so that two instances can be compared without false negatives.
pub fn drain_into(&mut self, other: &mut ChangeBatch<T>) where
T: Clone,
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T: Clone,
Drains self
into other
.
This method has similar a effect to calling other.extend(self.drain())
, but has the
opportunity to optimize this to a ::std::mem::swap(self, other)
when other
is empty.
As many uses of this method are to propagate updates, this optimization can be quite
handy.
Examples
use timely::progress::ChangeBatch; let mut batch1 = ChangeBatch::<usize>::new_from(17, 1); let mut batch2 = ChangeBatch::new(); batch1.drain_into(&mut batch2); assert!(batch1.is_empty()); assert!(!batch2.is_empty());
pub fn compact(&mut self)
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Compact the internal representation.
This method sort self.updates
and consolidates elements with equal item, discarding
any whose accumulation is zero. It is optimized to only do this if the number of dirty
elements is non-zero.
pub fn unstable_internal_updates(&self) -> &Vec<(T, i64)>
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Expose the internal vector of updates.
pub fn unstable_internal_clean(&self) -> usize
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Expose the internal value of clean
.
Trait Implementations
impl<T: PartialEq> PartialEq<ChangeBatch<T>> for ChangeBatch<T>
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fn eq(&self, other: &ChangeBatch<T>) -> bool
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fn ne(&self, other: &ChangeBatch<T>) -> bool
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impl<T: Clone> Clone for ChangeBatch<T>
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fn clone(&self) -> ChangeBatch<T>
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fn clone_from(&mut self, source: &Self)
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Performs copy-assignment from source
. Read more
impl<T: Eq> Eq for ChangeBatch<T>
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impl<T: Debug> Debug for ChangeBatch<T>
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Auto Trait Implementations
impl<T> Send for ChangeBatch<T> where
T: Send,
T: Send,
impl<T> Sync for ChangeBatch<T> where
T: Sync,
T: Sync,
Blanket Implementations
impl<T> Data for T where
T: 'static + Clone,
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T: 'static + Clone,
impl<T, U> Into for T where
U: From<T>,
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U: From<T>,
impl<T> ToOwned for T where
T: Clone,
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T: Clone,
impl<T> From for T
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impl<T, U> TryFrom for T where
U: Into<T>,
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U: Into<T>,
type Error = Infallible
The type returned in the event of a conversion error.
fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>
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impl<T> Borrow for T where
T: ?Sized,
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T: ?Sized,
impl<T> BorrowMut for T where
T: ?Sized,
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T: ?Sized,
fn borrow_mut(&mut self) -> &mut T
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impl<T, U> TryInto for T where
U: TryFrom<T>,
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U: TryFrom<T>,
type Error = <U as TryFrom<T>>::Error
The type returned in the event of a conversion error.
fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>
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impl<T> Any for T where
T: 'static + ?Sized,
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T: 'static + ?Sized,