p2p/discv5: added new topic discovery package

p2p/discv5/topic_test.go

@@ -0,0 +1,71 @@
+// Copyright 2015 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library 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 Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+package discv5
+
+import (
+	"encoding/binary"
+	"testing"
+	"time"
+
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/common/mclock"
+)
+
+func TestTopicRadius(t *testing.T) {
+	now := mclock.Now()
+	topic := Topic("qwerty")
+	rad := newTopicRadius(topic)
+	targetRad := (^uint64(0)) / 100
+
+	waitFn := func(addr common.Hash) time.Duration {
+		prefix := binary.BigEndian.Uint64(addr[0:8])
+		dist := prefix ^ rad.topicHashPrefix
+		relDist := float64(dist) / float64(targetRad)
+		relTime := (1 - relDist/2) * 2
+		if relTime < 0 {
+			relTime = 0
+		}
+		return time.Duration(float64(targetWaitTime) * relTime)
+	}
+
+	bcnt := 0
+	cnt := 0
+	var sum float64
+	for cnt < 100 {
+		addr := rad.nextTarget(false).target
+		wait := waitFn(addr)
+		ticket := &ticket{
+			topics:  []Topic{topic},
+			regTime: []mclock.AbsTime{mclock.AbsTime(wait)},
+			node:    &Node{nodeNetGuts: nodeNetGuts{sha: addr}},
+		}
+		rad.adjustWithTicket(now, addr, ticketRef{ticket, 0})
+		if rad.radius != maxRadius {
+			cnt++
+			sum += float64(rad.radius)
+		} else {
+			bcnt++
+			if bcnt > 500 {
+				t.Errorf("Radius did not converge in 500 iterations")
+			}
+		}
+	}
+	avgRel := sum / float64(cnt) / float64(targetRad)
+	if avgRel > 1.05 || avgRel < 0.95 {
+		t.Errorf("Average/target ratio is too far from 1 (%v)", avgRel)
+	}
+}