Implement math stats precompile

.gitmodules

@@ -9,8 +9,8 @@
 	url = https://github.com/google/brotli.git
 [submodule "contracts"]
 	path = contracts
-	url = https://github.com/VannaLabs/nitro-contracts.git
-	branch = develop
+	url = https://github.com/adambalogh/nitro-contracts.git
+	branch = main
 [submodule "arbitrator/wasm-testsuite/testsuite"]
 	path = arbitrator/wasm-testsuite/testsuite
 	url = https://github.com/WebAssembly/testsuite.git

go.mod

@@ -268,6 +268,7 @@ require (
 	golang.org/x/exp v0.0.0-20230321023759-10a507213a29 // indirect
 	golang.org/x/mod v0.10.0 // indirect
 	golang.org/x/xerrors v0.0.0-20220907171357-04be3eba64a2 // indirect
+	gonum.org/v1/gonum v0.14.0 // indirect
 	google.golang.org/genproto v0.0.0-20231016165738-49dd2c1f3d0b // indirect
 	google.golang.org/genproto/googleapis/api v0.0.0-20231012201019-e917dd12ba7a // indirect
 	google.golang.org/genproto/googleapis/rpc v0.0.0-20231030173426-d783a09b4405 // indirect

go.sum

@@ -2077,6 +2077,8 @@ golang.org/x/xerrors v0.0.0-20191204190536-9bdfabe68543/go.mod h1:I/5z698sn9Ka8T
 golang.org/x/xerrors v0.0.0-20200804184101-5ec99f83aff1/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
 golang.org/x/xerrors v0.0.0-20220907171357-04be3eba64a2 h1:H2TDz8ibqkAF6YGhCdN3jS9O0/s90v0rJh3X/OLHEUk=
 golang.org/x/xerrors v0.0.0-20220907171357-04be3eba64a2/go.mod h1:K8+ghG5WaK9qNqU5K3HdILfMLy1f3aNYFI/wnl100a8=
+gonum.org/v1/gonum v0.14.0 h1:2NiG67LD1tEH0D7kM+ps2V+fXmsAnpUeec7n8tcr4S0=
+gonum.org/v1/gonum v0.14.0/go.mod h1:AoWeoz0becf9QMWtE8iWXNXc27fK4fNeHNf/oMejGfU=
 google.golang.org/api v0.0.0-20180910000450-7ca32eb868bf/go.mod h1:4mhQ8q/RsB7i+udVvVy5NUi08OU8ZlA0gRVgrF7VFY0=
 google.golang.org/api v0.0.0-20181030000543-1d582fd0359e/go.mod h1:4mhQ8q/RsB7i+udVvVy5NUi08OU8ZlA0gRVgrF7VFY0=
 google.golang.org/api v0.1.0/go.mod h1:UGEZY7KEX120AnNLIHFMKIo4obdJhkp2tPbaPlQx13Y=

precompiles/ArbInference.go

@@ -1,6 +1,7 @@
 package precompiles
 
 import (
+	// #nosec G501
 	"crypto/md5"
 	"encoding/hex"
 	"strconv"
@@ -127,6 +128,8 @@ func HashInferenceTX(arr []string, separator string) string {
 	for i := 0; i < len(arr); i++ {
 		hashString += arr[i] + separator
 	}
+
+	// #nosec G401
 	hasher := md5.New()
 	hasher.Write([]byte(hashString))
 	return hex.EncodeToString(hasher.Sum(nil))

precompiles/ArbMathStats.go

@@ -0,0 +1,28 @@
+package precompiles
+
+import (
+	"math"
+	"math/big"
+
+	"gonum.org/v1/gonum/stat"
+)
+
+// ArbMathStats provides methods for computing statistics
+type ArbMathStats struct {
+	Address addr // 0x11b
+}
+
+func (con *ArbMathStats) StdDev(c ctx, evm mech, input []int32, decimals uint8) (huge, error) {
+	floatInput := make([]float64, len(input))
+	for i, num := range input {
+		floatInput[i] = float64(num)
+	}
+
+	stdev := big.NewFloat(stat.StdDev(floatInput, nil))
+	stdev.Mul(stdev, big.NewFloat(math.Pow10(int(decimals))))
+
+	truncatedStdev := new(big.Int)
+	stdev.Int(truncatedStdev)
+
+	return truncatedStdev, nil
+}

precompiles/ArbMathStats_test.go

@@ -0,0 +1,35 @@
+package precompiles
+
+import (
+	"math/big"
+	"testing"
+)
+
+func TestArbMathStatsStandardDeviationIdenticalElements(t *testing.T) {
+	mathStats := ArbMathStats{}
+
+	data := []int32{1, 1, 1, 1, 1, 1}
+	stdev, _ := mathStats.stdDev(nil, nil, data, 0)
+
+	if stdev.Cmp(big.NewInt(0)) != 0 {
+		t.Errorf("Expected stdev of 0 for identical elements, got: %s", stdev)
+	}
+}
+
+func TestArbMathStatsStandardDeviation(t *testing.T) {
+	mathStats := ArbMathStats{}
+
+	data := []int32{1, 5, 10, 100}
+
+	stdev, _ := mathStats.stdDev(nil, nil, data, 4)
+	expected := big.NewInt(474763)
+	if stdev.Cmp(expected) != 0 {
+		t.Errorf("Incorrect stddev, expected %s, got %s", expected, stdev)
+	}
+
+	stdev, _ = mathStats.stdDev(nil, nil, data, 2)
+	expected = big.NewInt(4747)
+	if stdev.Cmp(expected) != 0 {
+		t.Errorf("Incorrect stddev, expected %s, got %s", expected, stdev)
+	}
+}

precompiles/precompile.go

@@ -541,6 +541,7 @@ func Precompiles() map[addr]ArbosPrecompile {
 	insert(MakePrecompile(templates.ArbAggregatorMetaData, &ArbAggregator{Address: hex("6d")}))
 	insert(MakePrecompile(templates.ArbStatisticsMetaData, &ArbStatistics{Address: hex("6f")}))
 	insert(MakePrecompile(templates.ArbInferenceMetaData, &ArbInference{Address: hex("11a")}))
+	insert(MakePrecompile(templates.ArbMathStatsMetaData, &ArbMathStats{Address: hex("11b")}))
 
 	eventCtx := func(gasLimit uint64, err error) *Context {
 		if err != nil {