From 639139795b33369154e540a0e6ba552619790f8a Mon Sep 17 00:00:00 2001
From: whyrusleeping <why@ipfs.io>
Date: Thu, 26 Sep 2019 16:09:10 -0700
Subject: [PATCH] remember why the go big math library works the way it does

---
 chain/vm/vm.go      | 36 +++++++-----------------------------
 chain/vm/vm_test.go | 20 --------------------
 2 files changed, 7 insertions(+), 49 deletions(-)

diff --git a/chain/vm/vm.go b/chain/vm/vm.go
index 3cd88a2c9..6616e8312 100644
--- a/chain/vm/vm.go
+++ b/chain/vm/vm.go
@@ -633,36 +633,14 @@ func DepositFunds(act *types.Actor, amt types.BigInt) {
 	act.Balance = types.BigAdd(act.Balance, amt)
 }
 
+var IV = types.BigInt{big.NewInt(0).SetBytes(build.MiningRewardInitialAttoFilBytes)}
+var miningRewardTotal = types.FromFil(build.MiningRewardTotal)
+
 // MiningReward returns correct mining reward
 //   coffer is amount of FIL in NetworkAddress
 func MiningReward(coffer types.BigInt) types.BigInt {
-	i := &big.Int{}
-	i.SetBytes(build.MiningRewardInitialAttoFilBytes)
-	IV := types.BigInt{i}
-	res := types.BigMul(IV, coffer)
-	res = types.BigDiv(res, types.FromFil(build.MiningRewardTotal))
-	return res
+	ci := big.NewInt(0).Set(coffer.Int)
+	res := ci.Mul(ci, IV.Int)
+	res = res.Div(res, miningRewardTotal.Int)
+	return types.BigInt{res}
 }
-
-/*
-func MiningRewardForBlock(height uint64) types.BigInt {
-
-	//decay := e^(ln(0.5) / (HalvingPeriodBlocks / AdjustmentPeriod)
-	decay := 0.9977808404048861
-
-	totalMiningReward := types.FromFil(build.MiningRewardTotal)
-
-	dval := big.NewFloat(math.Pow(decay, float64(uint64(height/build.AdjustmentPeriod))))
-
-	iv := big.NewFloat(0).Mul(
-		big.NewFloat(0).SetInt(totalMiningReward.Int),
-		big.NewFloat(1-decay),
-	)
-
-	//return (InitialReward * Math.pow(decay, Math.floor(height / adjustmentPeriod))) / adjustmentPeriod
-
-	reward, _ := big.NewFloat(0).Quo(iv.Mul(iv, dval), big.NewFloat(build.AdjustmentPeriod)).Int(nil)
-
-	return types.BigInt{reward}
-}
-*/
diff --git a/chain/vm/vm_test.go b/chain/vm/vm_test.go
index b1fcc34c4..1c31bc729 100644
--- a/chain/vm/vm_test.go
+++ b/chain/vm/vm_test.go
@@ -2,7 +2,6 @@ package vm
 
 import (
 	"fmt"
-	"os"
 	"testing"
 
 	"github.com/filecoin-project/go-lotus/build"
@@ -14,10 +13,6 @@ func TestBlockReward(t *testing.T) {
 	sum := types.NewInt(0)
 	N := build.HalvingPeriodBlocks
 	for i := 0; i < N; i++ {
-		if i%20000 == 0 {
-			fmt.Fprintf(os.Stderr, "%.1f%%\r", float64(i)/float64(N)*100)
-		}
-
 		a := MiningReward(coffer)
 		sum = types.BigAdd(sum, a)
 		coffer = types.BigSub(coffer, a)
@@ -29,19 +24,4 @@ func TestBlockReward(t *testing.T) {
 	fmt.Printf("Total reward: %d\n", build.MiningRewardTotal)
 	fmt.Printf("Remaining: %s\n", types.BigDiv(coffer, types.NewInt(build.FilecoinPrecision)))
 	fmt.Printf("Given out: %s\n", types.BigDiv(sum, types.NewInt(build.FilecoinPrecision)))
-
-	for i := 0; i < N; i++ {
-		if i%20000 == 0 {
-			fmt.Fprintf(os.Stderr, "%.1f%%\r", float64(i)/float64(N)*100)
-		}
-
-		a := MiningReward(coffer)
-		sum = types.BigAdd(sum, a)
-		coffer = types.BigSub(coffer, a)
-	}
-
-	fmt.Println("Next halving period")
-	fmt.Printf("Total reward: %d\n", build.MiningRewardTotal)
-	fmt.Printf("Remaining: %s\n", types.BigDiv(coffer, types.NewInt(build.FilecoinPrecision)))
-	fmt.Printf("Given out: %s\n", types.BigDiv(sum, types.NewInt(build.FilecoinPrecision)))
 }