refactor: emulated clean up fixes #448 (#449)

* refactor: step 1 clean up api and builder wrapper

* refactor: PackElementLimbs PackFull -> packLimbs

* refactor: added field.NewElement

* refactor: remove deadcode from builder stuff, update stats with constraining inputs

* build: restore golangci-lint conf

* refactor: emulated.NewConstant -> emulated.FromConstant

* refactor: emulated.FromConstant -> emulated.ValueOf

* fix: ensure we alwways constrain witness limbs

* fix: fix optimisation test bound with constrained limbs

* perf: constraint to modulus width the witness limbs

examples/emulated/emulated_test.go

@@ -16,9 +16,9 @@ func TestEmulatedArithmetic(t *testing.T) {
 
 	var circuit, witness Circuit
 
-	witness.X = emulated.NewElement[emulated.Secp256k1Fp]("26959946673427741531515197488526605382048662297355296634326893985793")
-	witness.Y = emulated.NewElement[emulated.Secp256k1Fp]("53919893346855483063030394977053210764097324594710593268653787971586")
-	witness.Res = emulated.NewElement[emulated.Secp256k1Fp]("485279052387156144224396168012515269674445015885648619762653195154800")
+	witness.X = emulated.ValueOf[emulated.Secp256k1Fp]("26959946673427741531515197488526605382048662297355296634326893985793")
+	witness.Y = emulated.ValueOf[emulated.Secp256k1Fp]("53919893346855483063030394977053210764097324594710593268653787971586")
+	witness.Res = emulated.ValueOf[emulated.Secp256k1Fp]("485279052387156144224396168012515269674445015885648619762653195154800")
 
 	assert.ProverSucceeded(&circuit, &witness, test.WithCurves(ecc.BN254), test.WithBackends(backend.GROTH16), test.NoSerialization())
 }

frontend/builder.go

@@ -2,7 +2,6 @@ package frontend
 
 import (
 	"math/big"
-	"reflect"
 
 	"github.com/consensys/gnark/backend/hint"
 	"github.com/consensys/gnark/constraint"
@@ -66,10 +65,6 @@ type Builder interface {
 	// Compile is called after circuit.Define() to produce a final IR (ConstraintSystem)
 	Compile() (constraint.ConstraintSystem, error)
 
-	// VariableCount returns the number of native elements required to represent
-	// the given reflected type as a witness.
-	VariableCount(reflect.Type) int
-
 	// PublicVariable is called by the compiler when parsing the circuit schema. It panics if
 	// called inside circuit.Define()
 	PublicVariable(schema.LeafInfo) Variable

frontend/compile.go

@@ -36,7 +36,7 @@ func Compile(field *big.Int, newBuilder NewBuilder, circuit Circuit, opts ...Com
 	log := logger.Logger()
 	log.Info().Msg("compiling circuit")
 	// parse options
-	opt := CompileConfig{wrapper: func(b Builder) Builder { return b }}
+	opt := CompileConfig{}
 	for _, o := range opts {
 		if err := o(&opt); err != nil {
 			log.Err(err).Msg("applying compile option")
@@ -50,7 +50,6 @@ func Compile(field *big.Int, newBuilder NewBuilder, circuit Circuit, opts ...Com
 		log.Err(err).Msg("instantiating builder")
 		return nil, fmt.Errorf("new compiler: %w", err)
 	}
-	builder = opt.wrapper(builder)
 
 	// parse the circuit builds a schema of the circuit
 	// and call circuit.Define() method to initialize a list of constraints in the compiler
@@ -75,11 +74,6 @@ func parseCircuit(builder Builder, circuit Circuit) (err error) {
 		return err
 	}
 
-	// we scale the number of secret and public variables by n;
-	// scs and r1cs builder always return 1. Emulated arithmetic returns number of limbs per variable.
-	n := builder.VariableCount(nil)
-	s.Public *= n
-	s.Secret *= n
 	log := logger.Logger()
 	log.Info().Int("nbSecret", s.Secret).Int("nbPublic", s.Public).Msg("parsed circuit inputs")
 
@@ -140,7 +134,6 @@ type CompileOption func(opt *CompileConfig) error
 type CompileConfig struct {
 	Capacity                  int
 	IgnoreUnconstrainedInputs bool
-	wrapper                   BuilderWrapper
 	CompressThreshold         int
 }
 
@@ -168,19 +161,6 @@ func IgnoreUnconstrainedInputs() CompileOption {
 	}
 }
 
-// BuilderWrapper wraps existing Builder.
-type BuilderWrapper func(Builder) Builder
-
-// WithBuilderWrapper is a compile option which wraps the builder before parsing
-// the schema and calling Define method of the circuit. If not set, then the
-// builder returned by the NewBuilder is directly used.
-func WithBuilderWrapper(wrapper BuilderWrapper) CompileOption {
-	return func(opt *CompileConfig) error {
-		opt.wrapper = wrapper
-		return nil
-	}
-}
-
 // WithCompressThreshold is a compile option which enforces automatic variable
 // compression if the length of the linear expression in the variable exceeds
 // given threshold.

frontend/cs/r1cs/builder.go

@@ -125,11 +125,6 @@ func (builder *builder) newInternalVariable() expr.LinearExpression {
 	return expr.NewLinearExpression(idx, builder.tOne)
 }
 
-func (builder *builder) VariableCount(t reflect.Type) int {
-	// TODO @gbotrel refactor?
-	return 1
-}
-
 // PublicVariable creates a new public Variable
 func (builder *builder) PublicVariable(f schema.LeafInfo) frontend.Variable {
 	idx := builder.cs.AddPublicVariable(f.FullName())

frontend/cs/scs/builder.go

@@ -145,10 +145,6 @@ func (builder *scs) newInternalVariable() expr.TermToRefactor {
 	return expr.NewTermToRefactor(idx, constraint.CoeffIdOne)
 }
 
-func (builder *scs) VariableCount(t reflect.Type) int {
-	return 1
-}
-
 // PublicVariable creates a new Public Variable
 func (builder *scs) PublicVariable(f schema.LeafInfo) frontend.Variable {
 	idx := builder.cs.AddPublicVariable(f.FullName())

internal/stats/snippet.go

@@ -80,22 +80,27 @@ func initSnippets() {
 		_ = mimc.Sum()
 	})
 	registerSnippet("math/emulated/secp256k1_64", func(api frontend.API, newVariable func() frontend.Variable) {
-		secp256k1, _ := emulated.NewAPI[emulated.Secp256k1Fp](api)
+		secp256k1, _ := emulated.NewField[emulated.Secp256k1Fp](api)
 
-		newElement := func() emulated.Element[emulated.Secp256k1Fp] {
-			r := emulated.NewElement[emulated.Secp256k1Fp](nil)
-			for i := 0; i < len(r.Limbs); i++ {
-				r.Limbs[i] = newVariable()
+		newElement := func() *emulated.Element[emulated.Secp256k1Fp] {
+			limbs := make([]frontend.Variable, emulated.Secp256k1Fp{}.NbLimbs())
+			for i := 0; i < len(limbs); i++ {
+				limbs[i] = newVariable()
 			}
-			return r
+			return secp256k1.NewElement(limbs)
 		}
 
-		x13 := secp256k1.Mul(newElement(), newElement(), newElement())
-		fx2 := secp256k1.Mul(5, newElement())
+		x13 := secp256k1.Mul(newElement(), newElement())
+		x13 = secp256k1.Mul(x13, newElement())
+		five := emulated.ValueOf[emulated.Secp256k1Fp](5)
+		fx2 := secp256k1.Mul(&five, newElement())
 		nom := secp256k1.Sub(fx2, x13)
-		denom := secp256k1.Add(newElement(), newElement(), newElement(), newElement())
+		denom := secp256k1.Add(newElement(), newElement())
+		denom = secp256k1.Add(denom, newElement())
+		denom = secp256k1.Add(denom, newElement())
 		free := secp256k1.Div(nom, denom)
-		res := secp256k1.Add(x13, fx2, free)
+		res := secp256k1.Add(x13, fx2)
+		res = secp256k1.Add(res, free)
 		secp256k1.AssertIsEqual(res, newElement())
 	})
 

std/algebra/weierstrass/doc_test.go

@@ -23,9 +23,9 @@ func (c *ExampleCurveCircuit[B, S]) Define(api frontend.API) error {
 		panic("initalize new curve")
 	}
 	G := curve.Generator()
-	scalar4 := emulated.NewElement[S](4)
+	scalar4 := emulated.ValueOf[S](4)
 	g4 := curve.ScalarMul(G, &scalar4) // 4*G
-	scalar5 := emulated.NewElement[S](5)
+	scalar5 := emulated.ValueOf[S](5)
 	g5 := curve.ScalarMul(G, &scalar5) // 5*G
 	g9 := curve.Add(g4, g5)            // 9*G
 	curve.AssertIsEqual(g9, &c.Res)
@@ -41,8 +41,8 @@ func ExampleCurve() {
 	circuit := ExampleCurveCircuit[emulated.Secp256k1Fp, emulated.Secp256k1Fr]{}
 	witness := ExampleCurveCircuit[emulated.Secp256k1Fp, emulated.Secp256k1Fr]{
 		Res: weierstrass.AffinePoint[emulated.Secp256k1Fp]{
-			X: emulated.NewElement[emulated.Secp256k1Fp](secpCurve.Gx),
-			Y: emulated.NewElement[emulated.Secp256k1Fp](secpCurve.Gy),
+			X: emulated.ValueOf[emulated.Secp256k1Fp](secpCurve.Gx),
+			Y: emulated.ValueOf[emulated.Secp256k1Fp](secpCurve.Gy),
 		},
 	}
 	ccs, err := frontend.Compile(ecc.BN254.ScalarField(), r1cs.NewBuilder, &circuit)

std/algebra/weierstrass/point.go

@@ -21,8 +21,8 @@ func New[Base, Scalars emulated.FieldParams](api frontend.API, params CurveParam
 	if err != nil {
 		return nil, fmt.Errorf("new scalar api: %w", err)
 	}
-	Gx := emulated.NewElement[Base](params.Gx)
-	Gy := emulated.NewElement[Base](params.Gy)
+	Gx := emulated.ValueOf[Base](params.Gx)
+	Gy := emulated.ValueOf[Base](params.Gy)
 	return &Curve[Base, Scalars]{
 		params:    params,
 		api:       api,
@@ -32,7 +32,7 @@ func New[Base, Scalars emulated.FieldParams](api frontend.API, params CurveParam
 			X: Gx,
 			Y: Gy,
 		},
-		a:    emulated.NewElement[Base](params.A),
+		a:    emulated.ValueOf[Base](params.A),
 		addA: params.A.Cmp(big.NewInt(0)) != 0,
 	}, nil
 }

std/algebra/weierstrass/point_test.go

@@ -36,12 +36,12 @@ func TestNeg(t *testing.T) {
 	circuit := NegTest[emulated.Secp256k1Fp, emulated.Secp256k1Fr]{}
 	witness := NegTest[emulated.Secp256k1Fp, emulated.Secp256k1Fr]{
 		P: AffinePoint[emulated.Secp256k1Fp]{
-			X: emulated.NewElement[emulated.Secp256k1Fp](secpCurve.Gx),
-			Y: emulated.NewElement[emulated.Secp256k1Fp](secpCurve.Gy),
+			X: emulated.ValueOf[emulated.Secp256k1Fp](secpCurve.Gx),
+			Y: emulated.ValueOf[emulated.Secp256k1Fp](secpCurve.Gy),
 		},
 		Q: AffinePoint[emulated.Secp256k1Fp]{
-			X: emulated.NewElement[emulated.Secp256k1Fp](secpCurve.Gx),
-			Y: emulated.NewElement[emulated.Secp256k1Fp](yn),
+			X: emulated.ValueOf[emulated.Secp256k1Fp](secpCurve.Gx),
+			Y: emulated.ValueOf[emulated.Secp256k1Fp](yn),
 		},
 	}
 	err := test.IsSolved(&circuit, &witness, testCurve.ScalarField())
@@ -70,16 +70,16 @@ func TestAdd(t *testing.T) {
 	circuit := AddTest[emulated.Secp256k1Fp, emulated.Secp256k1Fr]{}
 	witness := AddTest[emulated.Secp256k1Fp, emulated.Secp256k1Fr]{
 		P: AffinePoint[emulated.Secp256k1Fp]{
-			X: emulated.NewElement[emulated.Secp256k1Fp](secpCurve.Gx),
-			Y: emulated.NewElement[emulated.Secp256k1Fp](secpCurve.Gy),
+			X: emulated.ValueOf[emulated.Secp256k1Fp](secpCurve.Gx),
+			Y: emulated.ValueOf[emulated.Secp256k1Fp](secpCurve.Gy),
 		},
 		Q: AffinePoint[emulated.Secp256k1Fp]{
-			X: emulated.NewElement[emulated.Secp256k1Fp](xd),
-			Y: emulated.NewElement[emulated.Secp256k1Fp](yd),
+			X: emulated.ValueOf[emulated.Secp256k1Fp](xd),
+			Y: emulated.ValueOf[emulated.Secp256k1Fp](yd),
 		},
 		R: AffinePoint[emulated.Secp256k1Fp]{
-			X: emulated.NewElement[emulated.Secp256k1Fp](xa),
-			Y: emulated.NewElement[emulated.Secp256k1Fp](ya),
+			X: emulated.ValueOf[emulated.Secp256k1Fp](xa),
+			Y: emulated.ValueOf[emulated.Secp256k1Fp](ya),
 		},
 	}
 	err := test.IsSolved(&circuit, &witness, testCurve.ScalarField())
@@ -107,12 +107,12 @@ func TestDouble(t *testing.T) {
 	circuit := DoubleTest[emulated.Secp256k1Fp, emulated.Secp256k1Fr]{}
 	witness := DoubleTest[emulated.Secp256k1Fp, emulated.Secp256k1Fr]{
 		P: AffinePoint[emulated.Secp256k1Fp]{
-			X: emulated.NewElement[emulated.Secp256k1Fp](secpCurve.Gx),
-			Y: emulated.NewElement[emulated.Secp256k1Fp](secpCurve.Gy),
+			X: emulated.ValueOf[emulated.Secp256k1Fp](secpCurve.Gx),
+			Y: emulated.ValueOf[emulated.Secp256k1Fp](secpCurve.Gy),
 		},
 		Q: AffinePoint[emulated.Secp256k1Fp]{
-			X: emulated.NewElement[emulated.Secp256k1Fp](xd),
-			Y: emulated.NewElement[emulated.Secp256k1Fp](yd),
+			X: emulated.ValueOf[emulated.Secp256k1Fp](xd),
+			Y: emulated.ValueOf[emulated.Secp256k1Fp](yd),
 		},
 	}
 	err := test.IsSolved(&circuit, &witness, testCurve.ScalarField())
@@ -143,14 +143,14 @@ func TestScalarMul(t *testing.T) {
 
 	circuit := ScalarMulTest[emulated.Secp256k1Fp, emulated.Secp256k1Fr]{}
 	witness := ScalarMulTest[emulated.Secp256k1Fp, emulated.Secp256k1Fr]{
-		S: emulated.NewElement[emulated.Secp256k1Fr](s),
+		S: emulated.ValueOf[emulated.Secp256k1Fr](s),
 		P: AffinePoint[emulated.Secp256k1Fp]{
-			X: emulated.NewElement[emulated.Secp256k1Fp](secpCurve.Gx),
-			Y: emulated.NewElement[emulated.Secp256k1Fp](secpCurve.Gy),
+			X: emulated.ValueOf[emulated.Secp256k1Fp](secpCurve.Gx),
+			Y: emulated.ValueOf[emulated.Secp256k1Fp](secpCurve.Gy),
 		},
 		Q: AffinePoint[emulated.Secp256k1Fp]{
-			X: emulated.NewElement[emulated.Secp256k1Fp](sx),
-			Y: emulated.NewElement[emulated.Secp256k1Fp](sy),
+			X: emulated.ValueOf[emulated.Secp256k1Fp](sx),
+			Y: emulated.ValueOf[emulated.Secp256k1Fp](sy),
 		},
 	}
 	err := test.IsSolved(&circuit, &witness, testCurve.ScalarField())
@@ -169,14 +169,14 @@ func TestScalarMul2(t *testing.T) {
 
 	circuit := ScalarMulTest[emulated.BN254Fp, emulated.BN254Fr]{}
 	witness := ScalarMulTest[emulated.BN254Fp, emulated.BN254Fr]{
-		S: emulated.NewElement[emulated.BN254Fr](s),
+		S: emulated.ValueOf[emulated.BN254Fr](s),
 		P: AffinePoint[emulated.BN254Fp]{
-			X: emulated.NewElement[emulated.BN254Fp](gen.X.BigInt(new(big.Int))),
-			Y: emulated.NewElement[emulated.BN254Fp](gen.Y.BigInt(new(big.Int))),
+			X: emulated.ValueOf[emulated.BN254Fp](gen.X.BigInt(new(big.Int))),
+			Y: emulated.ValueOf[emulated.BN254Fp](gen.Y.BigInt(new(big.Int))),
 		},
 		Q: AffinePoint[emulated.BN254Fp]{
-			X: emulated.NewElement[emulated.BN254Fp](res.X.BigInt(new(big.Int))),
-			Y: emulated.NewElement[emulated.BN254Fp](res.Y.BigInt(new(big.Int))),
+			X: emulated.ValueOf[emulated.BN254Fp](res.X.BigInt(new(big.Int))),
+			Y: emulated.ValueOf[emulated.BN254Fp](res.Y.BigInt(new(big.Int))),
 		},
 	}
 	err := test.IsSolved(&circuit, &witness, testCurve.ScalarField())

std/math/emulated/composition_test.go

@@ -17,6 +17,7 @@ func TestComposition(t *testing.T) {
 }
 
 func testComposition[T FieldParams](t *testing.T) {
+	t.Helper()
 	assert := test.NewAssert(t)
 	var fp T
 	assert.Run(func(assert *test.Assert) {

std/math/emulated/doc_example_field_test.go

@@ -33,9 +33,9 @@ func (c *ExampleFieldCircuit[T]) Define(api frontend.API) error {
 func ExampleField() {
 	circuit := ExampleFieldCircuit[emulated.BN254Fp]{}
 	witness := ExampleFieldCircuit[emulated.BN254Fp]{
-		In1: emulated.NewElement[emulated.BN254Fp](3),
-		In2: emulated.NewElement[emulated.BN254Fp](5),
-		Res: emulated.NewElement[emulated.BN254Fp](15),
+		In1: emulated.ValueOf[emulated.BN254Fp](3),
+		In2: emulated.ValueOf[emulated.BN254Fp](5),
+		Res: emulated.ValueOf[emulated.BN254Fp](15),
 	}
 	ccs, err := frontend.Compile(ecc.BN254.ScalarField(), r1cs.NewBuilder, &circuit)
 	if err != nil {