eth/downloader: prioritize block fetch based on chain position, cap memory use

6 files changed, 429 insertions, 0 deletions

diff --git a/Godeps/Godeps.json b/Godeps/Godeps.json
index 2480ff9a2..a5b27e76c 100644
--- a/Godeps/Godeps.json
+++ b/Godeps/Godeps.json
@@ -99,6 +99,10 @@
 			"Rev": "27c40922c40b43fe04554d8223a402af3ea333f3"
 		},
 		{
+			"ImportPath": "gopkg.in/karalabe/cookiejar.v2/collections/prque",
+			"Rev": "cf5d8079df7c4501217638e1e3a6e43f94822548"
+		},
+		{
 			"ImportPath": "gopkg.in/qml.v1/cdata",
 			"Rev": "1116cb9cd8dee23f8d444ded354eb53122739f99"
 		},
diff --git a/Godeps/_workspace/src/gopkg.in/karalabe/cookiejar.v2/collections/prque/example_test.go b/Godeps/_workspace/src/gopkg.in/karalabe/cookiejar.v2/collections/prque/example_test.go
new file mode 100644
index 000000000..7b2e5ee84
--- /dev/null
+++ b/Godeps/_workspace/src/gopkg.in/karalabe/cookiejar.v2/collections/prque/example_test.go
@@ -0,0 +1,44 @@
+// CookieJar - A contestant's algorithm toolbox
+// Copyright (c) 2013 Peter Szilagyi. All rights reserved.
+//
+// CookieJar is dual licensed: you can redistribute it and/or modify it under
+// the terms of the GNU General Public License as published by the Free Software
+// Foundation, either version 3 of the License, or (at your option) any later
+// version.
+//
+// The toolbox is distributed in the hope that it will be useful, but WITHOUT
+// ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+// FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+// more details.
+//
+// Alternatively, the CookieJar toolbox may be used in accordance with the terms
+// and conditions contained in a signed written agreement between you and the
+// author(s).
+
+package prque_test
+
+import (
+	"fmt"
+
+	"gopkg.in/karalabe/cookiejar.v2/collections/prque"
+)
+
+// Insert some data into a priority queue and pop them out in prioritized order.
+func Example_usage() {
+	// Define some data to push into the priority queue
+	prio := []float32{77.7, 22.2, 44.4, 55.5, 11.1, 88.8, 33.3, 99.9, 0.0, 66.6}
+	data := []string{"zero", "one", "two", "three", "four", "five", "six", "seven", "eight", "nine"}
+
+	// Create the priority queue and insert the prioritized data
+	pq := prque.New()
+	for i := 0; i < len(data); i++ {
+		pq.Push(data[i], prio[i])
+	}
+	// Pop out the data and print them
+	for !pq.Empty() {
+		val, prio := pq.Pop()
+		fmt.Printf("%.1f:%s ", prio, val)
+	}
+	// Output:
+	// 99.9:seven 88.8:five 77.7:zero 66.6:nine 55.5:three 44.4:two 33.3:six 22.2:one 11.1:four 0.0:eight
+}
diff --git a/Godeps/_workspace/src/gopkg.in/karalabe/cookiejar.v2/collections/prque/prque.go b/Godeps/_workspace/src/gopkg.in/karalabe/cookiejar.v2/collections/prque/prque.go
new file mode 100644
index 000000000..8225e8c53
--- /dev/null
+++ b/Godeps/_workspace/src/gopkg.in/karalabe/cookiejar.v2/collections/prque/prque.go
@@ -0,0 +1,75 @@
+// CookieJar - A contestant's algorithm toolbox
+// Copyright (c) 2013 Peter Szilagyi. All rights reserved.
+//
+// CookieJar is dual licensed: you can redistribute it and/or modify it under
+// the terms of the GNU General Public License as published by the Free Software
+// Foundation, either version 3 of the License, or (at your option) any later
+// version.
+//
+// The toolbox is distributed in the hope that it will be useful, but WITHOUT
+// ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+// FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+// more details.
+//
+// Alternatively, the CookieJar toolbox may be used in accordance with the terms
+// and conditions contained in a signed written agreement between you and the
+// author(s).
+
+// Package prque implements a priority queue data structure supporting arbitrary
+// value types and float priorities.
+//
+// The reasoning behind using floats for the priorities vs. ints or interfaces
+// was larger flexibility without sacrificing too much performance or code
+// complexity.
+//
+// If you would like to use a min-priority queue, simply negate the priorities.
+//
+// Internally the queue is based on the standard heap package working on a
+// sortable version of the block based stack.
+package prque
+
+import (
+	"container/heap"
+)
+
+// Priority queue data structure.
+type Prque struct {
+	cont *sstack
+}
+
+// Creates a new priority queue.
+func New() *Prque {
+	return &Prque{newSstack()}
+}
+
+// Pushes a value with a given priority into the queue, expanding if necessary.
+func (p *Prque) Push(data interface{}, priority float32) {
+	heap.Push(p.cont, &item{data, priority})
+}
+
+// Pops the value with the greates priority off the stack and returns it.
+// Currently no shrinking is done.
+func (p *Prque) Pop() (interface{}, float32) {
+	item := heap.Pop(p.cont).(*item)
+	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
+}
+
+// Checks whether the priority queue is empty.
+func (p *Prque) Empty() bool {
+	return p.cont.Len() == 0
+}
+
+// Returns the number of element in the priority queue.
+func (p *Prque) Size() int {
+	return p.cont.Len()
+}
+
+// Clears the contents of the priority queue.
+func (p *Prque) Reset() {
+	p.cont.Reset()
+}
diff --git a/Godeps/_workspace/src/gopkg.in/karalabe/cookiejar.v2/collections/prque/prque_test.go b/Godeps/_workspace/src/gopkg.in/karalabe/cookiejar.v2/collections/prque/prque_test.go
new file mode 100644
index 000000000..811c53c73
--- /dev/null
+++ b/Godeps/_workspace/src/gopkg.in/karalabe/cookiejar.v2/collections/prque/prque_test.go
@@ -0,0 +1,110 @@
+// CookieJar - A contestant's algorithm toolbox
+// Copyright (c) 2013 Peter Szilagyi. All rights reserved.
+//
+// CookieJar is dual licensed: you can redistribute it and/or modify it under
+// the terms of the GNU General Public License as published by the Free Software
+// Foundation, either version 3 of the License, or (at your option) any later
+// version.
+//
+// The toolbox is distributed in the hope that it will be useful, but WITHOUT
+// ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+// FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+// more details.
+//
+// Alternatively, the CookieJar toolbox may be used in accordance with the terms
+// and conditions contained in a signed written agreement between you and the
+// author(s).
+
+package prque
+
+import (
+	"math/rand"
+	"testing"
+)
+
+func TestPrque(t *testing.T) {
+	// Generate a batch of random data and a specific priority order
+	size := 16 * blockSize
+	prio := rand.Perm(size)
+	data := make([]int, size)
+	for i := 0; i < size; i++ {
+		data[i] = rand.Int()
+	}
+	queue := New()
+	for rep := 0; rep < 2; rep++ {
+		// Fill a priority queue with the above data
+		for i := 0; i < size; i++ {
+			queue.Push(data[i], float32(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[float32]int)
+		for i := 0; i < size; i++ {
+			dict[float32(prio[i])] = data[i]
+		}
+		// Pop out the elements in priority order and verify them
+		prevPrio := float32(size + 1)
+		for !queue.Empty() {
+			val, prio := queue.Pop()
+			if prio > prevPrio {
+				t.Errorf("invalid priority order: %v after %v.", prio, prevPrio)
+			}
+			prevPrio = prio
+			if val != dict[prio] {
+				t.Errorf("push/pop mismatch: have %v, want %v.", val, dict[prio])
+			}
+			delete(dict, prio)
+		}
+	}
+}
+
+func TestReset(t *testing.T) {
+	// Fill the queue with some random data
+	size := 16 * blockSize
+	queue := New()
+	for i := 0; i < size; i++ {
+		queue.Push(rand.Int(), rand.Float32())
+	}
+	// Reset and ensure it's empty
+	queue.Reset()
+	if !queue.Empty() {
+		t.Errorf("priority queue not empty after reset: %v", queue)
+	}
+}
+
+func BenchmarkPush(b *testing.B) {
+	// Create some initial data
+	data := make([]int, b.N)
+	prio := make([]float32, b.N)
+	for i := 0; i < len(data); i++ {
+		data[i] = rand.Int()
+		prio[i] = rand.Float32()
+	}
+	// Execute the benchmark
+	b.ResetTimer()
+	queue := New()
+	for i := 0; i < len(data); i++ {
+		queue.Push(data[i], prio[i])
+	}
+}
+
+func BenchmarkPop(b *testing.B) {
+	// Create some initial data
+	data := make([]int, b.N)
+	prio := make([]float32, b.N)
+	for i := 0; i < len(data); i++ {
+		data[i] = rand.Int()
+		prio[i] = rand.Float32()
+	}
+	queue := New()
+	for i := 0; i < len(data); i++ {
+		queue.Push(data[i], prio[i])
+	}
+	// Execute the benchmark
+	b.ResetTimer()
+	for !queue.Empty() {
+		queue.Pop()
+	}
+}
diff --git a/Godeps/_workspace/src/gopkg.in/karalabe/cookiejar.v2/collections/prque/sstack.go b/Godeps/_workspace/src/gopkg.in/karalabe/cookiejar.v2/collections/prque/sstack.go
new file mode 100644
index 000000000..55375a091
--- /dev/null
+++ b/Godeps/_workspace/src/gopkg.in/karalabe/cookiejar.v2/collections/prque/sstack.go
@@ -0,0 +1,103 @@
+// CookieJar - A contestant's algorithm toolbox
+// Copyright (c) 2013 Peter Szilagyi. All rights reserved.
+//
+// CookieJar is dual licensed: you can redistribute it and/or modify it under
+// the terms of the GNU General Public License as published by the Free Software
+// Foundation, either version 3 of the License, or (at your option) any later
+// version.
+//
+// The toolbox is distributed in the hope that it will be useful, but WITHOUT
+// ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+// FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+// more details.
+//
+// Alternatively, the CookieJar toolbox may be used in accordance with the terms
+// and conditions contained in a signed written agreement between you and the
+// author(s).
+
+package prque
+
+// The size of a block of data
+const blockSize = 4096
+
+// A prioritized item in the sorted stack.
+type item struct {
+	value    interface{}
+	priority float32
+}
+
+// Internal sortable stack data structure. Implements the Push and Pop ops for
+// the stack (heap) functionality and the Len, Less and Swap methods for the
+// sortability requirements of the heaps.
+type sstack struct {
+	size     int
+	capacity int
+	offset   int
+
+	blocks [][]*item
+	active []*item
+}
+
+// Creates a new, empty stack.
+func newSstack() *sstack {
+	result := new(sstack)
+	result.active = make([]*item, blockSize)
+	result.blocks = [][]*item{result.active}
+	result.capacity = blockSize
+	return result
+}
+
+// Pushes a value onto the stack, expanding it if necessary. Required by
+// heap.Interface.
+func (s *sstack) Push(data interface{}) {
+	if s.size == s.capacity {
+		s.active = make([]*item, blockSize)
+		s.blocks = append(s.blocks, s.active)
+		s.capacity += blockSize
+		s.offset = 0
+	} else if s.offset == blockSize {
+		s.active = s.blocks[s.size/blockSize]
+		s.offset = 0
+	}
+	s.active[s.offset] = data.(*item)
+	s.offset++
+	s.size++
+}
+
+// Pops a value off the stack and returns it. Currently no shrinking is done.
+// Required by heap.Interface.
+func (s *sstack) Pop() (res interface{}) {
+	s.size--
+	s.offset--
+	if s.offset < 0 {
+		s.offset = blockSize - 1
+		s.active = s.blocks[s.size/blockSize]
+	}
+	res, s.active[s.offset] = s.active[s.offset], nil
+	return
+}
+
+// Returns the length of the stack. Required by sort.Interface.
+func (s *sstack) Len() int {
+	return s.size
+}
+
+// Compares the priority of two elements of the stack (higher is first).
+// Required by sort.Interface.
+func (s *sstack) Less(i, j int) bool {
+	return s.blocks[i/blockSize][i%blockSize].priority > s.blocks[j/blockSize][j%blockSize].priority
+}
+
+// Swapts two elements in the stack. Required by sort.Interface.
+func (s *sstack) Swap(i, j int) {
+	ib, io, jb, jo := i/blockSize, i%blockSize, j/blockSize, j%blockSize
+	s.blocks[ib][io], s.blocks[jb][jo] = s.blocks[jb][jo], s.blocks[ib][io]
+}
+
+// Resets the stack, effectively clearing its contents.
+func (s *sstack) Reset() {
+	s.size = 0
+	s.offset = 0
+	s.active = s.blocks[0]
+	s.capacity = blockSize
+}
diff --git a/Godeps/_workspace/src/gopkg.in/karalabe/cookiejar.v2/collections/prque/sstack_test.go b/Godeps/_workspace/src/gopkg.in/karalabe/cookiejar.v2/collections/prque/sstack_test.go
new file mode 100644
index 000000000..7bdc08bf5
--- /dev/null
+++ b/Godeps/_workspace/src/gopkg.in/karalabe/cookiejar.v2/collections/prque/sstack_test.go
@@ -0,0 +1,93 @@
+// CookieJar - A contestant's algorithm toolbox
+// Copyright (c) 2013 Peter Szilagyi. All rights reserved.
+//
+// CookieJar is dual licensed: you can redistribute it and/or modify it under
+// the terms of the GNU General Public License as published by the Free Software
+// Foundation, either version 3 of the License, or (at your option) any later
+// version.
+//
+// The toolbox is distributed in the hope that it will be useful, but WITHOUT
+// ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+// FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+// more details.
+//
+// Alternatively, the CookieJar toolbox may be used in accordance with the terms
+// and conditions contained in a signed written agreement between you and the
+// author(s).
+
+package prque
+
+import (
+	"math/rand"
+	"sort"
+	"testing"
+)
+
+func TestSstack(t *testing.T) {
+	// Create some initial data
+	size := 16 * blockSize
+	data := make([]*item, size)
+	for i := 0; i < size; i++ {
+		data[i] = &item{rand.Int(), rand.Float32()}
+	}
+	stack := newSstack()
+	for rep := 0; rep < 2; rep++ {
+		// Push all the data into the stack, pop out every second
+		secs := []*item{}
+		for i := 0; i < size; i++ {
+			stack.Push(data[i])
+			if i%2 == 0 {
+				secs = append(secs, stack.Pop().(*item))
+			}
+		}
+		rest := []*item{}
+		for stack.Len() > 0 {
+			rest = append(rest, stack.Pop().(*item))
+		}
+		// Make sure the contents of the resulting slices are ok
+		for i := 0; i < size; i++ {
+			if i%2 == 0 && data[i] != secs[i/2] {
+				t.Errorf("push/pop mismatch: have %v, want %v.", secs[i/2], data[i])
+			}
+			if i%2 == 1 && data[i] != rest[len(rest)-i/2-1] {
+				t.Errorf("push/pop mismatch: have %v, want %v.", rest[len(rest)-i/2-1], data[i])
+			}
+		}
+	}
+}
+
+func TestSstackSort(t *testing.T) {
+	// Create some initial data
+	size := 16 * blockSize
+	data := make([]*item, size)
+	for i := 0; i < size; i++ {
+		data[i] = &item{rand.Int(), float32(i)}
+	}
+	// Push all the data into the stack
+	stack := newSstack()
+	for _, val := range data {
+		stack.Push(val)
+	}
+	// Sort and pop the stack contents (should reverse the order)
+	sort.Sort(stack)
+	for _, val := range data {
+		out := stack.Pop()
+		if out != val {
+			t.Errorf("push/pop mismatch after sort: have %v, want %v.", out, val)
+		}
+	}
+}
+
+func TestSstackReset(t *testing.T) {
+	// Push some stuff onto the stack
+	size := 16 * blockSize
+	stack := newSstack()
+	for i := 0; i < size; i++ {
+		stack.Push(&item{i, float32(i)})
+	}
+	// Clear and verify
+	stack.Reset()
+	if stack.Len() != 0 {
+		t.Errorf("stack not empty after reset: %v", stack)
+	}
+}