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common/prque: generic priority queue (ethereum#26290)
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* common, core, eth, les, trie: make prque generic

* les/vflux/server: fixed issues in priorityPool

* common, core, eth, les, trie: make priority also generic in prque

* les/flowcontrol: add test case for priority accumulator overflow

* les/flowcontrol: avoid priority value overflow

* common/prque: use int priority in some tests

No need to convert to int64 when we can just change the type used by the
queue.

* common/prque: remove comment about int64 range

---------

Co-authored-by: Zsolt Felfoldi <zsfelfoldi@gmail.com>
Co-authored-by: Felix Lange <fjl@twurst.com>
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@karalabe @zsfelfoldi
@fjl @shekhirin
3 people authored and shekhirin committed Jun 6, 2023
1 parent 050c082 commit ad50a5e
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Showing 20 changed files with 277 additions and 264 deletions.
78 changes: 38 additions & 40 deletions common/prque/lazyqueue.go
View file
Original file line number Diff line number Diff line change
Expand Up @@ -21,6 +21,7 @@ import (
"time"

"github.com/ethereum/go-ethereum/common/mclock"
"golang.org/x/exp/constraints"
)

// LazyQueue is a priority queue data structure where priorities can change over
Expand All @@ -32,31 +33,31 @@ import (
//
// If the upper estimate is exceeded then Update should be called for that item.
// A global Refresh function should also be called periodically.
type LazyQueue struct {
type LazyQueue[P constraints.Ordered, V any] struct {
clock mclock.Clock
// Items are stored in one of two internal queues ordered by estimated max
// priority until the next and the next-after-next refresh. Update and Refresh
// always places items in queue[1].
queue [2]*sstack
popQueue *sstack
queue [2]*sstack[P, V]
popQueue *sstack[P, V]
period time.Duration
maxUntil mclock.AbsTime
indexOffset int
setIndex SetIndexCallback
priority PriorityCallback
maxPriority MaxPriorityCallback
setIndex SetIndexCallback[V]
priority PriorityCallback[P, V]
maxPriority MaxPriorityCallback[P, V]
lastRefresh1, lastRefresh2 mclock.AbsTime
}

type (
PriorityCallback func(data interface{}) int64 // actual priority callback
MaxPriorityCallback func(data interface{}, until mclock.AbsTime) int64 // estimated maximum priority callback
PriorityCallback[P constraints.Ordered, V any] func(data V) P // actual priority callback
MaxPriorityCallback[P constraints.Ordered, V any] func(data V, until mclock.AbsTime) P // estimated maximum priority callback
)

// NewLazyQueue creates a new lazy queue
func NewLazyQueue(setIndex SetIndexCallback, priority PriorityCallback, maxPriority MaxPriorityCallback, clock mclock.Clock, refreshPeriod time.Duration) *LazyQueue {
q := &LazyQueue{
popQueue: newSstack(nil, false),
func NewLazyQueue[P constraints.Ordered, V any](setIndex SetIndexCallback[V], priority PriorityCallback[P, V], maxPriority MaxPriorityCallback[P, V], clock mclock.Clock, refreshPeriod time.Duration) *LazyQueue[P, V] {
q := &LazyQueue[P, V]{
popQueue: newSstack[P, V](nil),
setIndex: setIndex,
priority: priority,
maxPriority: maxPriority,
Expand All @@ -71,13 +72,13 @@ func NewLazyQueue(setIndex SetIndexCallback, priority PriorityCallback, maxPrior
}

// Reset clears the contents of the queue
func (q *LazyQueue) Reset() {
q.queue[0] = newSstack(q.setIndex0, false)
q.queue[1] = newSstack(q.setIndex1, false)
func (q *LazyQueue[P, V]) Reset() {
q.queue[0] = newSstack[P, V](q.setIndex0)
q.queue[1] = newSstack[P, V](q.setIndex1)
}

// Refresh performs queue re-evaluation if necessary
func (q *LazyQueue) Refresh() {
func (q *LazyQueue[P, V]) Refresh() {
now := q.clock.Now()
for time.Duration(now-q.lastRefresh2) >= q.period*2 {
q.refresh(now)
Expand All @@ -87,33 +88,33 @@ func (q *LazyQueue) Refresh() {
}

// refresh re-evaluates items in the older queue and swaps the two queues
func (q *LazyQueue) refresh(now mclock.AbsTime) {
func (q *LazyQueue[P, V]) refresh(now mclock.AbsTime) {
q.maxUntil = now.Add(q.period)
for q.queue[0].Len() != 0 {
q.Push(heap.Pop(q.queue[0]).(*item).value)
q.Push(heap.Pop(q.queue[0]).(*item[P, V]).value)
}
q.queue[0], q.queue[1] = q.queue[1], q.queue[0]
q.indexOffset = 1 - q.indexOffset
q.maxUntil = q.maxUntil.Add(q.period)
}

// Push adds an item to the queue
func (q *LazyQueue) Push(data interface{}) {
heap.Push(q.queue[1], &item{data, q.maxPriority(data, q.maxUntil)})
func (q *LazyQueue[P, V]) Push(data V) {
heap.Push(q.queue[1], &item[P, V]{data, q.maxPriority(data, q.maxUntil)})
}

// Update updates the upper priority estimate for the item with the given queue index
func (q *LazyQueue) Update(index int) {
func (q *LazyQueue[P, V]) Update(index int) {
q.Push(q.Remove(index))
}

// Pop removes and returns the item with the greatest actual priority
func (q *LazyQueue) Pop() (interface{}, int64) {
func (q *LazyQueue[P, V]) Pop() (V, P) {
var (
resData interface{}
resPri int64
resData V
resPri P
)
q.MultiPop(func(data interface{}, priority int64) bool {
q.MultiPop(func(data V, priority P) bool {
resData = data
resPri = priority
return false
Expand All @@ -123,7 +124,7 @@ func (q *LazyQueue) Pop() (interface{}, int64) {

// peekIndex returns the index of the internal queue where the item with the
// highest estimated priority is or -1 if both are empty
func (q *LazyQueue) peekIndex() int {
func (q *LazyQueue[P, V]) peekIndex() int {
if q.queue[0].Len() != 0 {
if q.queue[1].Len() != 0 && q.queue[1].blocks[0][0].priority > q.queue[0].blocks[0][0].priority {
return 1
Expand All @@ -139,17 +140,17 @@ func (q *LazyQueue) peekIndex() int {
// MultiPop pops multiple items from the queue and is more efficient than calling
// Pop multiple times. Popped items are passed to the callback. MultiPop returns
// when the callback returns false or there are no more items to pop.
func (q *LazyQueue) MultiPop(callback func(data interface{}, priority int64) bool) {
func (q *LazyQueue[P, V]) MultiPop(callback func(data V, priority P) bool) {
nextIndex := q.peekIndex()
for nextIndex != -1 {
data := heap.Pop(q.queue[nextIndex]).(*item).value
heap.Push(q.popQueue, &item{data, q.priority(data)})
data := heap.Pop(q.queue[nextIndex]).(*item[P, V]).value
heap.Push(q.popQueue, &item[P, V]{data, q.priority(data)})
nextIndex = q.peekIndex()
for q.popQueue.Len() != 0 && (nextIndex == -1 || q.queue[nextIndex].blocks[0][0].priority < q.popQueue.blocks[0][0].priority) {
i := heap.Pop(q.popQueue).(*item)
i := heap.Pop(q.popQueue).(*item[P, V])
if !callback(i.value, i.priority) {
for q.popQueue.Len() != 0 {
q.Push(heap.Pop(q.popQueue).(*item).value)
q.Push(heap.Pop(q.popQueue).(*item[P, V]).value)
}
return
}
Expand All @@ -159,31 +160,28 @@ func (q *LazyQueue) MultiPop(callback func(data interface{}, priority int64) boo
}

// PopItem pops the item from the queue only, dropping the associated priority value.
func (q *LazyQueue) PopItem() interface{} {
func (q *LazyQueue[P, V]) PopItem() V {
i, _ := q.Pop()
return i
}

// Remove removes the item with the given index.
func (q *LazyQueue) Remove(index int) interface{} {
if index < 0 {
return nil
}
return heap.Remove(q.queue[index&1^q.indexOffset], index>>1).(*item).value
func (q *LazyQueue[P, V]) Remove(index int) V {
return heap.Remove(q.queue[index&1^q.indexOffset], index>>1).(*item[P, V]).value
}

// Empty checks whether the priority queue is empty.
func (q *LazyQueue) Empty() bool {
func (q *LazyQueue[P, V]) Empty() bool {
return q.queue[0].Len() == 0 && q.queue[1].Len() == 0
}

// Size returns the number of items in the priority queue.
func (q *LazyQueue) Size() int {
func (q *LazyQueue[P, V]) Size() int {
return q.queue[0].Len() + q.queue[1].Len()
}

// setIndex0 translates internal queue item index to the virtual index space of LazyQueue
func (q *LazyQueue) setIndex0(data interface{}, index int) {
func (q *LazyQueue[P, V]) setIndex0(data V, index int) {
if index == -1 {
q.setIndex(data, -1)
} else {
Expand All @@ -192,6 +190,6 @@ func (q *LazyQueue) setIndex0(data interface{}, index int) {
}

// setIndex1 translates internal queue item index to the virtual index space of LazyQueue
func (q *LazyQueue) setIndex1(data interface{}, index int) {
func (q *LazyQueue[P, V]) setIndex1(data V, index int) {
q.setIndex(data, index+index+1)
}
44 changes: 19 additions & 25 deletions common/prque/prque.go
View file
Original file line number Diff line number Diff line change
Expand Up @@ -19,65 +19,59 @@ package prque

import (
"container/heap"

"golang.org/x/exp/constraints"
)

// Priority queue data structure.
type Prque struct {
cont *sstack
type Prque[P constraints.Ordered, V any] struct {
cont *sstack[P, V]
}

// New creates a new priority queue.
func New(setIndex SetIndexCallback) *Prque {
return &Prque{newSstack(setIndex, false)}
}

// NewWrapAround creates a new priority queue with wrap-around priority handling.
func NewWrapAround(setIndex SetIndexCallback) *Prque {
return &Prque{newSstack(setIndex, true)}
func New[P constraints.Ordered, V any](setIndex SetIndexCallback[V]) *Prque[P, V] {
return &Prque[P, V]{newSstack[P, V](setIndex)}
}

// Pushes a value with a given priority into the queue, expanding if necessary.
func (p *Prque) Push(data interface{}, priority int64) {
heap.Push(p.cont, &item{data, priority})
func (p *Prque[P, V]) Push(data V, priority P) {
heap.Push(p.cont, &item[P, V]{data, priority})
}

// Peek returns the value with the greatest priority but does not pop it off.
func (p *Prque) Peek() (interface{}, int64) {
func (p *Prque[P, V]) Peek() (V, P) {
item := p.cont.blocks[0][0]
return item.value, item.priority
}

// Pops the value with the greatest priority off the stack and returns it.
// Currently no shrinking is done.
func (p *Prque) Pop() (interface{}, int64) {
item := heap.Pop(p.cont).(*item)
func (p *Prque[P, V]) Pop() (V, P) {
item := heap.Pop(p.cont).(*item[P, V])
return item.value, item.priority
}

// Pops only the item from the queue, dropping the associated priority value.
func (p *Prque) PopItem() interface{} {
return heap.Pop(p.cont).(*item).value
func (p *Prque[P, V]) PopItem() V {
return heap.Pop(p.cont).(*item[P, V]).value
}

// Remove removes the element with the given index.
func (p *Prque) Remove(i int) interface{} {
if i < 0 {
return nil
}
return heap.Remove(p.cont, i)
func (p *Prque[P, V]) Remove(i int) V {
return heap.Remove(p.cont, i).(*item[P, V]).value
}

// Checks whether the priority queue is empty.
func (p *Prque) Empty() bool {
func (p *Prque[P, V]) Empty() bool {
return p.cont.Len() == 0
}

// Returns the number of element in the priority queue.
func (p *Prque) Size() int {
func (p *Prque[P, V]) Size() int {
return p.cont.Len()
}

// Clears the contents of the priority queue.
func (p *Prque) Reset() {
*p = *New(p.cont.setIndex)
func (p *Prque[P, V]) Reset() {
*p = *New[P, V](p.cont.setIndex)
}
27 changes: 15 additions & 12 deletions common/prque/prque_test.go
View file
Original file line number Diff line number Diff line change
Expand Up @@ -21,22 +21,24 @@ func TestPrque(t *testing.T) {
for i := 0; i < size; i++ {
data[i] = rand.Int()
}
queue := New(nil)
queue := New[int, int](nil)

for rep := 0; rep < 2; rep++ {
// Fill a priority queue with the above data
for i := 0; i < size; i++ {
queue.Push(data[i], int64(prio[i]))
queue.Push(data[i], prio[i])
if queue.Size() != i+1 {
t.Errorf("queue size mismatch: have %v, want %v.", queue.Size(), i+1)
}
}
// Create a map the values to the priorities for easier verification
dict := make(map[int64]int)
dict := make(map[int]int)
for i := 0; i < size; i++ {
dict[int64(prio[i])] = data[i]
dict[prio[i]] = data[i]
}

// Pop out the elements in priority order and verify them
prevPrio := int64(size + 1)
prevPrio := size + 1
for !queue.Empty() {
val, prio := queue.Pop()
if prio > prevPrio {
Expand All @@ -59,22 +61,23 @@ func TestReset(t *testing.T) {
for i := 0; i < size; i++ {
data[i] = rand.Int()
}
queue := New(nil)
queue := New[int, int](nil)

for rep := 0; rep < 2; rep++ {
// Fill a priority queue with the above data
for i := 0; i < size; i++ {
queue.Push(data[i], int64(prio[i]))
queue.Push(data[i], prio[i])
if queue.Size() != i+1 {
t.Errorf("queue size mismatch: have %v, want %v.", queue.Size(), i+1)
}
}
// Create a map the values to the priorities for easier verification
dict := make(map[int64]int)
dict := make(map[int]int)
for i := 0; i < size; i++ {
dict[int64(prio[i])] = data[i]
dict[prio[i]] = data[i]
}
// Pop out half the elements in priority order and verify them
prevPrio := int64(size + 1)
prevPrio := size + 1
for i := 0; i < size/2; i++ {
val, prio := queue.Pop()
if prio > prevPrio {
Expand Down Expand Up @@ -104,7 +107,7 @@ func BenchmarkPush(b *testing.B) {
}
// Execute the benchmark
b.ResetTimer()
queue := New(nil)
queue := New[int64, int](nil)
for i := 0; i < len(data); i++ {
queue.Push(data[i], prio[i])
}
Expand All @@ -118,7 +121,7 @@ func BenchmarkPop(b *testing.B) {
data[i] = rand.Int()
prio[i] = rand.Int63()
}
queue := New(nil)
queue := New[int64, int](nil)
for i := 0; i < len(data); i++ {
queue.Push(data[i], prio[i])
}
Expand Down
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