Merge pull request #1588 from obscuren/diff-bomb

core, miner: added difficulty bomb

6 files changed, 196 insertions, 7 deletions

diff --git a/core/block_processor.go b/core/block_processor.go
index 6687cd000..5a2ad8377 100644
--- a/core/block_processor.go
+++ b/core/block_processor.go
@@ -386,7 +386,7 @@ func ValidateHeader(pow pow.PoW, block *types.Header, parent *types.Block, check
 		return BlockEqualTSErr
 	}
 
-	expd := CalcDifficulty(block.Time, parent.Time(), parent.Difficulty())
+	expd := CalcDifficulty(block.Time, parent.Time(), parent.Number(), parent.Difficulty())
 	if expd.Cmp(block.Difficulty) != 0 {
 		return fmt.Errorf("Difficulty check failed for block %v, %v", block.Difficulty, expd)
 	}
diff --git a/core/chain_makers.go b/core/chain_makers.go
index 283653d9a..85a6175dc 100644
--- a/core/chain_makers.go
+++ b/core/chain_makers.go
@@ -171,7 +171,7 @@ func makeHeader(parent *types.Block, state *state.StateDB) *types.Header {
 		Root:       state.Root(),
 		ParentHash: parent.Hash(),
 		Coinbase:   parent.Coinbase(),
-		Difficulty: CalcDifficulty(time, parent.Time(), parent.Difficulty()),
+		Difficulty: CalcDifficulty(time, parent.Time(), parent.Number(), parent.Difficulty()),
 		GasLimit:   CalcGasLimit(parent),
 		GasUsed:    new(big.Int),
 		Number:     new(big.Int).Add(parent.Number(), common.Big1),
diff --git a/core/chain_util.go b/core/chain_util.go
index 104670195..34f6c8d0a 100644
--- a/core/chain_util.go
+++ b/core/chain_util.go
@@ -30,14 +30,15 @@ import (
 )
 
 var (
-	blockHashPre = []byte("block-hash-")
-	blockNumPre  = []byte("block-num-")
+	blockHashPre  = []byte("block-hash-")
+	blockNumPre   = []byte("block-num-")
+	expDiffPeriod = big.NewInt(100000)
 )
 
 // CalcDifficulty is the difficulty adjustment algorithm. It returns
 // the difficulty that a new block b should have when created at time
 // given the parent block's time and difficulty.
-func CalcDifficulty(time, parentTime uint64, parentDiff *big.Int) *big.Int {
+func CalcDifficulty(time, parentTime uint64, parentNumber, parentDiff *big.Int) *big.Int {
 	diff := new(big.Int)
 	adjust := new(big.Int).Div(parentDiff, params.DifficultyBoundDivisor)
 	bigTime := new(big.Int)
@@ -52,8 +53,19 @@ func CalcDifficulty(time, parentTime uint64, parentDiff *big.Int) *big.Int {
 		diff.Sub(parentDiff, adjust)
 	}
 	if diff.Cmp(params.MinimumDifficulty) < 0 {
-		return params.MinimumDifficulty
+		diff = params.MinimumDifficulty
 	}
+
+	periodCount := new(big.Int).Add(parentNumber, common.Big1)
+	periodCount.Div(periodCount, expDiffPeriod)
+	if periodCount.Cmp(common.Big1) > 0 {
+		// diff = diff + 2^(periodCount - 2)
+		expDiff := periodCount.Sub(periodCount, common.Big2)
+		expDiff.Exp(common.Big2, expDiff, nil)
+		diff.Add(diff, expDiff)
+		diff = common.BigMax(diff, params.MinimumDifficulty)
+	}
+
 	return diff
 }
 
diff --git a/core/chain_util_test.go b/core/chain_util_test.go
new file mode 100644
index 000000000..4bbe81194
--- /dev/null
+++ b/core/chain_util_test.go
@@ -0,0 +1,77 @@
+// 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 core
+
+import (
+	"encoding/json"
+	"math/big"
+	"os"
+	"testing"
+
+	"github.com/ethereum/go-ethereum/common"
+)
+
+type diffTest struct {
+	ParentTimestamp    uint64
+	ParentDifficulty   *big.Int
+	CurrentTimestamp   uint64
+	CurrentBlocknumber *big.Int
+	CurrentDifficulty  *big.Int
+}
+
+func (d *diffTest) UnmarshalJSON(b []byte) (err error) {
+	var ext struct {
+		ParentTimestamp    string
+		ParentDifficulty   string
+		CurrentTimestamp   string
+		CurrentBlocknumber string
+		CurrentDifficulty  string
+	}
+	if err := json.Unmarshal(b, &ext); err != nil {
+		return err
+	}
+
+	d.ParentTimestamp = common.String2Big(ext.ParentTimestamp).Uint64()
+	d.ParentDifficulty = common.String2Big(ext.ParentDifficulty)
+	d.CurrentTimestamp = common.String2Big(ext.CurrentTimestamp).Uint64()
+	d.CurrentBlocknumber = common.String2Big(ext.CurrentBlocknumber)
+	d.CurrentDifficulty = common.String2Big(ext.CurrentDifficulty)
+
+	return nil
+}
+
+func TestDifficulty(t *testing.T) {
+	file, err := os.Open("../tests/files/BasicTests/difficulty.json")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer file.Close()
+
+	tests := make(map[string]diffTest)
+	err = json.NewDecoder(file).Decode(&tests)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	for name, test := range tests {
+		number := new(big.Int).Sub(test.CurrentBlocknumber, big.NewInt(1))
+		diff := CalcDifficulty(test.CurrentTimestamp, test.ParentTimestamp, number, test.ParentDifficulty)
+		if diff.Cmp(test.CurrentDifficulty) != 0 {
+			t.Error(name, "failed. Expected", test.CurrentDifficulty, "and calculated", diff)
+		}
+	}
+}
diff --git a/miner/worker.go b/miner/worker.go
index a703baada..269219ba0 100644
--- a/miner/worker.go
+++ b/miner/worker.go
@@ -445,7 +445,7 @@ func (self *worker) commitNewWork() {
 	header := &types.Header{
 		ParentHash: parent.Hash(),
 		Number:     num.Add(num, common.Big1),
-		Difficulty: core.CalcDifficulty(uint64(tstamp), parent.Time(), parent.Difficulty()),
+		Difficulty: core.CalcDifficulty(uint64(tstamp), parent.Time(), parent.Number(), parent.Difficulty()),
 		GasLimit:   core.CalcGasLimit(parent),
 		GasUsed:    new(big.Int),
 		Coinbase:   self.coinbase,
diff --git a/tests/files/BasicTests/difficulty.json b/tests/files/BasicTests/difficulty.json
new file mode 100644
index 000000000..44beac5f5
--- /dev/null
+++ b/tests/files/BasicTests/difficulty.json
@@ -0,0 +1,100 @@
+{
+    "preExpDiffIncrease" : {
+        "parentTimestamp" : "42",
+        "parentDifficulty" : "1000000",
+        "currentTimestamp" : "43",
+        "currentBlockNumber" : "42",
+        "currentDifficulty" : "1000488"
+    },
+    "preExpDiffDecrease" : {
+        "parentTimestamp" : "42",
+        "parentDifficulty" : "1000000",
+        "currentTimestamp" : "60",
+        "currentBlockNumber" : "42",
+        "currentDifficulty" : "999512"
+    },
+    "ExpDiffAtBlock200000Increase" : {
+        "parentTimestamp" : "42",
+        "parentDifficulty" : "1000000",
+        "currentTimestamp" : "43",
+        "currentBlockNumber" : "200000",
+        "currentDifficulty" : "1000489"
+    },
+    "ExpDiffAtBlock200000Decrease" : {
+        "parentTimestamp" : "42",
+        "parentDifficulty" : "1000000",
+        "currentTimestamp" : "60",
+        "currentBlockNumber" : "200000",
+        "currentDifficulty" : "999513"
+    },
+    "ExpDiffPostBlock200000Increase" : {
+        "parentTimestamp" : "42",
+        "parentDifficulty" : "1000000",
+        "currentTimestamp" : "43",
+        "currentBlockNumber" : "200001",
+        "currentDifficulty" : "1000489"
+    },
+    "ExpDiffPostBlock200000Decrease" : {
+        "parentTimestamp" : "42",
+        "parentDifficulty" : "1000000",
+        "currentTimestamp" : "60",
+        "currentBlockNumber" : "200001",
+        "currentDifficulty" : "999513"
+    },
+    "ExpDiffPreBlock300000Increase" : {
+        "parentTimestamp" : "42",
+        "parentDifficulty" : "1000000",
+        "currentTimestamp" : "43",
+        "currentBlockNumber" : "299999",
+        "currentDifficulty" : "1000489"
+    },
+    "ExpDiffPreBlock300000Decrease" : {
+        "parentTimestamp" : "42",
+        "parentDifficulty" : "1000000",
+        "currentTimestamp" : "60",
+        "currentBlockNumber" : "299999",
+        "currentDifficulty" : "999513"
+    },
+    "ExpDiffAtBlock300000Increase" : {
+        "parentTimestamp" : "42",
+        "parentDifficulty" : "1000000",
+        "currentTimestamp" : "43",
+        "currentBlockNumber" : "300000",
+        "currentDifficulty" : "1000490"
+    },
+    "ExpDiffAtBlock300000Decrease" : {
+        "parentTimestamp" : "42",
+        "parentDifficulty" : "1000000",
+        "currentTimestamp" : "60",
+        "currentBlockNumber" : "300000",
+        "currentDifficulty" : "999514"
+    },
+    "ExpDiffPostBlock300000Increase" : {
+        "parentTimestamp" : "42",
+        "parentDifficulty" : "1000000",
+        "currentTimestamp" : "43",
+        "currentBlockNumber" : "300001",
+        "currentDifficulty" : "1000490"
+    },
+    "ExpDiffPostBlock300000Decrease" : {
+        "parentTimestamp" : "42",
+        "parentDifficulty" : "1000000",
+        "currentTimestamp" : "60",
+        "currentBlockNumber" : "300001",
+        "currentDifficulty" : "999514"
+    },
+    "ExpDiffInAYearIncrease" : {
+        "parentTimestamp" : "42",
+        "parentDifficulty" : "1000000",
+        "currentTimestamp" : "43",
+        "currentBlockNumber" : "2302400",
+        "currentDifficulty" : "3097640"
+    },
+    "ExpDiffInAYearDecrease" : {
+        "parentTimestamp" : "42",
+        "parentDifficulty" : "1000000",
+        "currentTimestamp" : "60",
+        "currentBlockNumber" : "2302400",
+        "currentDifficulty" : "3096664"
+    }
+}