Merge pull request #86 from line/feature/cal_voter_num

 Add `CalNumOfVoterToElect` function to calculate the number of voter to elect

go.mod

@@ -8,6 +8,8 @@ require (
 	github.com/btcsuite/btcd v0.20.1-beta
 	github.com/btcsuite/btcutil v1.0.2
 	github.com/coniks-sys/coniks-go v0.0.0-20180722014011-11acf4819b71
+	github.com/datastream/go-fn v0.0.0-20130403065544-37331e464987 // indirect
+	github.com/datastream/probab v0.0.0-20150902151906-d47400db423d
 	github.com/fortytw2/leaktest v1.3.0
 	github.com/go-kit/kit v0.10.0
 	github.com/go-logfmt/logfmt v0.5.0
@@ -22,6 +24,7 @@ require (
 	github.com/r2ishiguro/vrf v0.0.0-20180716233122-192de52975eb
 	github.com/rcrowley/go-metrics v0.0.0-20200313005456-10cdbea86bc0
 	github.com/rs/cors v1.7.0
+	github.com/skelterjohn/go.matrix v0.0.0-20130517144113-daa59528eefd // indirect
 	github.com/snikch/goodman v0.0.0-20171125024755-10e37e294daa
 	github.com/spf13/cobra v1.0.0
 	github.com/spf13/viper v1.6.3

go.sum

@@ -71,6 +71,10 @@ github.com/cosmos/go-bip39 v0.0.0-20180819234021-555e2067c45d/go.mod h1:tSxLoYXy
 github.com/cpuguy83/go-md2man/v2 v2.0.0-20190314233015-f79a8a8ca69d/go.mod h1:maD7wRr/U5Z6m/iR4s+kqSMx2CaBsrgA7czyZG/E6dU=
 github.com/cpuguy83/go-md2man/v2 v2.0.0/go.mod h1:maD7wRr/U5Z6m/iR4s+kqSMx2CaBsrgA7czyZG/E6dU=
 github.com/creack/pty v1.1.7/go.mod h1:lj5s0c3V2DBrqTV7llrYr5NG6My20zk30Fl46Y7DoTY=
+github.com/datastream/go-fn v0.0.0-20130403065544-37331e464987 h1:S3JwKvmPJITKLLH7r3WYbBLjXu4lEZU9gFBLj01zaNU=
+github.com/datastream/go-fn v0.0.0-20130403065544-37331e464987/go.mod h1:bJl2ftsgvIWNGkufh7xMrXAATJUEdner7/2wCuHmVLI=
+github.com/datastream/probab v0.0.0-20150902151906-d47400db423d h1:wnkyVc4CQO5XlqF4RW4+y9qN05xY/frZn0IiT4Gi0qc=
+github.com/datastream/probab v0.0.0-20150902151906-d47400db423d/go.mod h1:qktd+m4xKlvhKU9bN9YipjWd79+vYDYb+N85egJl/NM=
 github.com/davecgh/go-spew v0.0.0-20171005155431-ecdeabc65495/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
@@ -335,6 +339,8 @@ github.com/sean-/seed v0.0.0-20170313163322-e2103e2c3529/go.mod h1:DxrIzT+xaE7yg
 github.com/shurcooL/sanitized_anchor_name v1.0.0/go.mod h1:1NzhyTcUVG4SuEtjjoZeVRXNmyL/1OwPU0+IJeTBvfc=
 github.com/sirupsen/logrus v1.2.0/go.mod h1:LxeOpSwHxABJmUn/MG1IvRgCAasNZTLOkJPxbbu5VWo=
 github.com/sirupsen/logrus v1.4.2/go.mod h1:tLMulIdttU9McNUspp0xgXVQah82FyeX6MwdIuYE2rE=
+github.com/skelterjohn/go.matrix v0.0.0-20130517144113-daa59528eefd h1:+ZLYzP9SYC3WU9buyb9H0l9DQxqVFOCkDG8QnNBMAlA=
+github.com/skelterjohn/go.matrix v0.0.0-20130517144113-daa59528eefd/go.mod h1:x7ui0Rh4QxcWEOgIfa3cr9q4W/wyLTDdzISxBmLVeX8=
 github.com/smartystreets/assertions v0.0.0-20180927180507-b2de0cb4f26d h1:zE9ykElWQ6/NYmHa3jpm/yHnI4xSofP+UP6SpjHcSeM=
 github.com/smartystreets/assertions v0.0.0-20180927180507-b2de0cb4f26d/go.mod h1:OnSkiWE9lh6wB0YB77sQom3nweQdgAjqCqsofrRNTgc=
 github.com/smartystreets/goconvey v1.6.4 h1:fv0U8FUIMPNf1L9lnHLvLhgicrIVChEkdzIKYqbNC9s=
@@ -423,9 +429,7 @@ golang.org/x/lint v0.0.0-20190313153728-d0100b6bd8b3/go.mod h1:6SW0HCj/g11FgYtHl
 golang.org/x/lint v0.0.0-20190930215403-16217165b5de/go.mod h1:6SW0HCj/g11FgYtHlgUYUwCkIfeOF89ocIRzGO/8vkc=
 golang.org/x/mod v0.0.0-20190513183733-4bf6d317e70e/go.mod h1:mXi4GBBbnImb6dmsKGUJ2LatrhH/nqhxcFungHvyanc=
 golang.org/x/mod v0.1.1-0.20191105210325-c90efee705ee/go.mod h1:QqPTAvyqsEbceGzBzNggFXnrqF1CaUcvgkdR5Ot7KZg=
-golang.org/x/mod v0.2.0 h1:KU7oHjnv3XNWfa5COkzUifxZmxp1TyI7ImMXqFxLwvQ=
 golang.org/x/mod v0.2.0/go.mod h1:s0Qsj1ACt9ePp/hMypM3fl4fZqREWJwdYDEqhRiZZUA=
-golang.org/x/mod v0.3.0 h1:RM4zey1++hCTbCVQfnWeKs9/IEsaBLA8vTkd0WVtmH4=
 golang.org/x/mod v0.3.0/go.mod h1:s0Qsj1ACt9ePp/hMypM3fl4fZqREWJwdYDEqhRiZZUA=
 golang.org/x/net v0.0.0-20180724234803-3673e40ba225/go.mod h1:mL1N/T3taQHkDXs73rZJwtUhF3w3ftmwwsq0BUmARs4=
 golang.org/x/net v0.0.0-20180826012351-8a410e7b638d/go.mod h1:mL1N/T3taQHkDXs73rZJwtUhF3w3ftmwwsq0BUmARs4=
@@ -496,7 +500,6 @@ golang.org/x/tools v0.0.0-20191029190741-b9c20aec41a5/go.mod h1:b+2E5dAYhXwXZwtn
 golang.org/x/tools v0.0.0-20191119224855-298f0cb1881e/go.mod h1:b+2E5dAYhXwXZwtnZ6UAqBI28+e2cm9otk0dWdXHAEo=
 golang.org/x/tools v0.0.0-20200103221440-774c71fcf114 h1:DnSr2mCsxyCE6ZgIkmcWUQY2R5cH/6wL7eIxEmQOMSE=
 golang.org/x/tools v0.0.0-20200103221440-774c71fcf114/go.mod h1:TB2adYChydJhpapKDTa4BR/hXlZSLoq2Wpct/0txZ28=
-golang.org/x/tools v0.0.0-20200519205726-57a9e4404bf7 h1:nm4zDh9WvH4jiuUpMY5RUsvOwrtTVVAsUaCdLW71hfY=
 golang.org/x/tools v0.0.0-20200519205726-57a9e4404bf7/go.mod h1:EkVYQZoAsY45+roYkvgYkIh4xh/qjgUK9TdY2XT94GE=
 golang.org/x/xerrors v0.0.0-20190717185122-a985d3407aa7/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
 golang.org/x/xerrors v0.0.0-20191011141410-1b5146add898/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=

types/voter_set.go

@@ -4,9 +4,11 @@ import (
 	"bytes"
 	"encoding/binary"
 	"fmt"
+	"math"
 	"sort"
 	"strings"
 
+	"github.com/datastream/probab/dst"
 	"github.com/pkg/errors"
 	"github.com/tendermint/tendermint/crypto/merkle"
 	"github.com/tendermint/tendermint/crypto/tmhash"
@@ -91,7 +93,7 @@ func (voters *VoterSet) Copy() *VoterSet {
 }
 
 // Forces recalculation of the set's total voting power.
-// Panics if total voting power is bigger than MaxTotalStakingPower.
+// Panics if total voting power is bigger than MaxTotalVotingPower.
 func (voters *VoterSet) updateTotalVotingPower() {
 	sum := int64(0)
 	for _, val := range voters.Voters {
@@ -491,3 +493,20 @@ func RandVoterSet(numVoters int, votingPower int64) (*ValidatorSet, *VoterSet, [
 	sort.Sort(PrivValidatorsByAddress(privValidators))
 	return vals, SelectVoter(vals, []byte{}), privValidators
 }
+
+// CalNumOfVoterToElect calculate the number of voter to elect and return the number.
+func CalNumOfVoterToElect(n int64, byzantineRatio float64, accuracy float64) int64 {
+	if byzantineRatio < 0 || byzantineRatio > 1 || accuracy < 0 || accuracy > 1 {
+		panic("byzantineRatio and accuracy should be the float between 0 and 1")
+	}
+	byzantine := int64(math.Floor(float64(n) * byzantineRatio))
+
+	for i := int64(1); i <= n; i++ {
+		q := dst.HypergeometricQtlFor(n, byzantine, i, accuracy)
+		if int64(q)*3 < i {
+			return i
+		}
+	}
+
+	return n
+}

types/voter_set_test.go

@@ -145,3 +145,18 @@ func TestSelectVoterMaxVarious(t *testing.T) {
 		}
 	}
 }
+
+func TestCalVotersNum(t *testing.T) {
+	total := int64(200)
+	byzantine := 0.2
+	accuracy := 0.99999
+	selection := CalNumOfVoterToElect(total, byzantine, accuracy)
+	assert.Equal(t, selection, int64(88))
+
+	total = int64(100)
+	selection = CalNumOfVoterToElect(total, byzantine, accuracy)
+	assert.Equal(t, selection, int64(58))
+
+	assert.Panics(t, func() { CalNumOfVoterToElect(total, 0.3, 10) })
+	assert.Panics(t, func() { CalNumOfVoterToElect(total, 1.1, 0.9999) })
+}