Add Rust implementation for DABA

Author: segeljakt

rust/src/daba/mod.rs

@@ -0,0 +1,151 @@
+use crate::FifoWindow;
+use alga::general::AbstractMonoid;
+use alga::general::Operator;
+use std::collections::VecDeque;
+use std::marker::PhantomData;
+
+#[derive(Clone)]
+pub struct DABA<Value, BinOp>
+where
+    Value: AbstractMonoid<BinOp> + Clone,
+    BinOp: Operator,
+{
+    // ith oldest value in FIFO order stored at vi = vals[i]
+    vals: VecDeque<Value>,
+    aggs: VecDeque<Value>,
+    // 0 ≤ l ≤ r ≤ a ≤ b ≤ aggs.len()
+    l: usize, // Left,  ∀p ∈ l...r−1 : aggs[p] = vals[p] ⊕ ... ⊕ vals[r−1]
+    r: usize, // Right, ∀p ∈ r...a−1 : aggs[p] = vals[R] ⊕ ... ⊕ vals[p]
+    a: usize, // Accum, ∀p ∈ a...b−1 : aggs[p] = vals[p] ⊕ ... ⊕ vals[b−1]
+    b: usize, // Back,  ∀p ∈ b...e−1 : aggs[p] = vals[B] ⊕ ... ⊕ vals[p]
+    op: PhantomData<BinOp>,
+}
+
+impl<Value, BinOp> FifoWindow<Value, BinOp> for DABA<Value, BinOp>
+where
+    Value: AbstractMonoid<BinOp> + Clone,
+    BinOp: Operator,
+{
+    fn new() -> Self {
+        Self {
+            vals: VecDeque::new(),
+            aggs: VecDeque::new(),
+            l: 0,
+            r: 0,
+            a: 0,
+            b: 0,
+            op: PhantomData,
+        }
+    }
+    fn push(&mut self, v: Value) {
+        self.aggs.push_back(self.agg_b().operate(&v));
+        self.vals.push_back(v);
+        self.fixup();
+    }
+    fn pop(&mut self) {
+        if self.vals.pop_front().is_some() {
+            self.aggs.pop_front();
+            self.l -= 1;
+            self.r -= 1;
+            self.a -= 1;
+            self.b -= 1;
+            self.fixup();
+        }
+    }
+    fn query(&self) -> Value {
+        self.agg_f().operate(&self.agg_b())
+    }
+    fn len(&self) -> usize {
+        self.vals.len()
+    }
+    fn is_empty(&self) -> bool {
+        self.vals.is_empty()
+    }
+}
+
+impl<Value, BinOp> DABA<Value, BinOp>
+where
+    Value: AbstractMonoid<BinOp> + Clone,
+    BinOp: Operator,
+{
+    #[inline(always)]
+    fn agg_f(&self) -> Value {
+        if self.aggs.is_empty() {
+            Value::identity()
+        } else {
+            self.aggs.front().unwrap().clone()
+        }
+    }
+    #[inline(always)]
+    fn agg_b(&self) -> Value {
+        if self.b == self.aggs.len() {
+            Value::identity()
+        } else {
+            self.aggs.back().unwrap().clone()
+        }
+    }
+    #[inline(always)]
+    fn agg_l(&self) -> Value {
+        if self.l == self.r {
+            Value::identity()
+        } else {
+            self.aggs[self.l].clone()
+        }
+    }
+    #[inline(always)]
+    fn agg_r(&self) -> Value {
+        if self.r == self.a {
+            Value::identity()
+        } else {
+            self.aggs[self.a - 1].clone()
+        }
+    }
+    #[inline(always)]
+    fn agg_a(&self) -> Value {
+        if self.a == self.b {
+            Value::identity()
+        } else {
+            self.aggs[self.a].clone()
+        }
+    }
+    fn fixup(&mut self) {
+        if self.b == 0 {
+            self.singleton()
+        } else {
+            if self.l == self.b {
+                self.flip()
+            }
+            if self.l == self.r {
+                self.shift()
+            } else {
+                self.shrink()
+            }
+        }
+    }
+    #[inline(always)]
+    fn singleton(&mut self) {
+        self.l = self.aggs.len();
+        self.r = self.l;
+        self.a = self.l;
+        self.b = self.l;
+    }
+    #[inline(always)]
+    fn flip(&mut self) {
+        self.l = 0;
+        self.a = self.aggs.len();
+        self.b = self.a;
+    }
+    #[inline(always)]
+    fn shift(&mut self) {
+        self.a += 1;
+        self.r += 1;
+        self.l += 1;
+    }
+    #[inline(always)]
+    fn shrink(&mut self) {
+        self.aggs[self.l] = self.agg_l().operate(&self.agg_r()).operate(&self.agg_a());
+        self.l += 1;
+        self.aggs[self.a - 1] = self.vals[self.a - 1].operate(&self.agg_a());
+        self.a -= 1;
+    }
+}

rust/src/lib.rs

@@ -57,3 +57,5 @@ pub mod two_stacks;
 /// Reactive-Aggregator
 pub mod reactive;
 
+/// De-Amortized Banker's Aggregator
+pub mod daba;

rust/tests/fifo_window.rs

@@ -141,10 +141,10 @@ where
 }
 
 test_matrix! {
-    test1 => [ recalc::ReCalc, soe::SoE, reactive::Reactive, two_stacks::TwoStacks ],
-    test2 => [ recalc::ReCalc, soe::SoE, reactive::Reactive, two_stacks::TwoStacks ],
-    test3 => [ recalc::ReCalc,           reactive::Reactive, two_stacks::TwoStacks ],
-    test4 => [ recalc::ReCalc, soe::SoE, reactive::Reactive, two_stacks::TwoStacks ],
-    test5 => [ recalc::ReCalc, soe::SoE, reactive::Reactive, two_stacks::TwoStacks ],
-    test6 => [ recalc::ReCalc, soe::SoE, reactive::Reactive, two_stacks::TwoStacks ]
+    test1 => [ recalc::ReCalc, soe::SoE, reactive::Reactive, two_stacks::TwoStacks, daba::DABA ],
+    test2 => [ recalc::ReCalc, soe::SoE, reactive::Reactive, two_stacks::TwoStacks, daba::DABA ],
+    test3 => [ recalc::ReCalc,           reactive::Reactive, two_stacks::TwoStacks, daba::DABA ],
+    test4 => [ recalc::ReCalc, soe::SoE, reactive::Reactive, two_stacks::TwoStacks, daba::DABA ],
+    test5 => [ recalc::ReCalc, soe::SoE, reactive::Reactive, two_stacks::TwoStacks, daba::DABA ],
+    test6 => [ recalc::ReCalc, soe::SoE, reactive::Reactive, two_stacks::TwoStacks, daba::DABA ]
 }