Merge pull request #210 from Consensys/204-solidify-notion-of-evaluat…

…ion-context2

Solidify Notion of Evaluation Context

pkg/air/expr.go

@@ -1,11 +1,9 @@
 package air
 
 import (
-	"math"
-
 	"github.com/consensys/gnark-crypto/ecc/bls12-377/fr"
-	"github.com/consensys/go-corset/pkg/schema"
 	sc "github.com/consensys/go-corset/pkg/schema"
+	"github.com/consensys/go-corset/pkg/trace"
 	"github.com/consensys/go-corset/pkg/util"
 )
 
@@ -17,7 +15,7 @@ import (
 // trace expansion).
 type Expr interface {
 	util.Boundable
-	schema.Evaluable
+	sc.Evaluable
 
 	// String produces a string representing this as an S-Expression.
 	String() string
@@ -44,7 +42,7 @@ type Add struct{ Args []Expr }
 
 // Context determines the evaluation context (i.e. enclosing module) for this
 // expression.
-func (p *Add) Context(schema sc.Schema) (uint, uint, bool) {
+func (p *Add) Context(schema sc.Schema) trace.Context {
 	return sc.JoinContexts[Expr](p.Args, schema)
 }
 
@@ -73,7 +71,7 @@ type Sub struct{ Args []Expr }
 
 // Context determines the evaluation context (i.e. enclosing module) for this
 // expression.
-func (p *Sub) Context(schema sc.Schema) (uint, uint, bool) {
+func (p *Sub) Context(schema sc.Schema) trace.Context {
 	return sc.JoinContexts[Expr](p.Args, schema)
 }
 
@@ -102,7 +100,7 @@ type Mul struct{ Args []Expr }
 
 // Context determines the evaluation context (i.e. enclosing module) for this
 // expression.
-func (p *Mul) Context(schema sc.Schema) (uint, uint, bool) {
+func (p *Mul) Context(schema sc.Schema) trace.Context {
 	return sc.JoinContexts[Expr](p.Args, schema)
 }
 
@@ -154,8 +152,8 @@ func NewConstCopy(val *fr.Element) Expr {
 
 // Context determines the evaluation context (i.e. enclosing module) for this
 // expression.
-func (p *Constant) Context(schema sc.Schema) (uint, uint, bool) {
-	return math.MaxUint, math.MaxUint, true
+func (p *Constant) Context(schema sc.Schema) trace.Context {
+	return trace.VoidContext()
 }
 
 // Add two expressions together, producing a third.
@@ -193,9 +191,9 @@ func NewColumnAccess(column uint, shift int) Expr {
 
 // Context determines the evaluation context (i.e. enclosing module) for this
 // expression.
-func (p *ColumnAccess) Context(schema sc.Schema) (uint, uint, bool) {
+func (p *ColumnAccess) Context(schema sc.Schema) trace.Context {
 	col := schema.Columns().Nth(p.Column)
-	return col.Module(), col.LengthMultiplier(), true
+	return col.Context()
 }
 
 // Add two expressions together, producing a third.

pkg/air/gadgets/bits.go

@@ -23,7 +23,7 @@ func ApplyBinaryGadget(col uint, schema *air.Schema) {
 	// Construct X * (X-1)
 	X_X_m1 := X.Mul(X_m1)
 	// Done!
-	schema.AddVanishingConstraint(fmt.Sprintf("%s:u1", name), column.Module(), column.LengthMultiplier(), nil, X_X_m1)
+	schema.AddVanishingConstraint(fmt.Sprintf("%s:u1", name), column.Context(), nil, X_X_m1)
 }
 
 // ApplyBitwidthGadget ensures all values in a given column fit within a given
@@ -45,7 +45,7 @@ func ApplyBitwidthGadget(col uint, nbits uint, schema *air.Schema) {
 	coefficient := fr.NewElement(1)
 	// Add decomposition assignment
 	index := schema.AddAssignment(
-		assignment.NewByteDecomposition(name, column.Module(), column.LengthMultiplier(), col, n))
+		assignment.NewByteDecomposition(name, column.Context(), col, n))
 	// Construct Columns
 	for i := uint(0); i < n; i++ {
 		// Create Column + Constraint
@@ -61,5 +61,5 @@ func ApplyBitwidthGadget(col uint, nbits uint, schema *air.Schema) {
 	X := air.NewColumnAccess(col, 0)
 	eq := X.Equate(sum)
 	// Construct column name
-	schema.AddVanishingConstraint(fmt.Sprintf("%s:u%d", name, nbits), column.Module(), column.LengthMultiplier(), nil, eq)
+	schema.AddVanishingConstraint(fmt.Sprintf("%s:u%d", name, nbits), column.Context(), nil, eq)
 }

pkg/air/gadgets/column_sort.go

@@ -38,10 +38,10 @@ func ApplyColumnSortGadget(col uint, sign bool, bitwidth uint, schema *air.Schem
 	}
 	// Add delta assignment
 	deltaIndex := schema.AddAssignment(
-		assignment.NewComputedColumn(column.Module(), deltaName, column.LengthMultiplier(), Xdiff))
+		assignment.NewComputedColumn(column.Context(), deltaName, Xdiff))
 	// Add necessary bitwidth constraints
 	ApplyBitwidthGadget(deltaIndex, bitwidth, schema)
 	// Configure constraint: Delta[k] = X[k] - X[k-1]
 	Dk := air.NewColumnAccess(deltaIndex, 0)
-	schema.AddVanishingConstraint(deltaName, column.Module(), column.LengthMultiplier(), nil, Dk.Equate(Xdiff))
+	schema.AddVanishingConstraint(deltaName, column.Context(), nil, Dk.Equate(Xdiff))
 }

pkg/air/gadgets/expand.go

@@ -20,23 +20,23 @@ func Expand(e air.Expr, schema *air.Schema) uint {
 		return ca.Column
 	}
 	// No optimisation, therefore expand using a computedcolumn
-	module, multiplier := sc.DetermineEnclosingModuleOfExpression(e, schema)
+	ctx := e.Context(schema)
 	// Determine computed column name
 	name := e.String()
 	// Look up column
-	index, ok := sc.ColumnIndexOf(schema, module, name)
+	index, ok := sc.ColumnIndexOf(schema, ctx.Module(), name)
 	// Add new column (if it does not already exist)
 	if !ok {
 		// Add computed column
-		index = schema.AddAssignment(assignment.NewComputedColumn(module, name, multiplier, e))
+		index = schema.AddAssignment(assignment.NewComputedColumn(ctx, name, e))
 	}
 	// Construct v == [e]
 	v := air.NewColumnAccess(index, 0)
 	// Construct 1 == e/e
 	eq_e_v := v.Equate(e)
 	// Ensure (e - v) == 0, where v is value of computed column.
 	c_name := fmt.Sprintf("[%s]", e.String())
-	schema.AddVanishingConstraint(c_name, module, multiplier, nil, eq_e_v)
+	schema.AddVanishingConstraint(c_name, ctx, nil, eq_e_v)
 	//
 	return index
 }

pkg/air/gadgets/lexicographic_sort.go

@@ -7,6 +7,7 @@ import (
 	"github.com/consensys/go-corset/pkg/air"
 	sc "github.com/consensys/go-corset/pkg/schema"
 	"github.com/consensys/go-corset/pkg/schema/assignment"
+	"github.com/consensys/go-corset/pkg/trace"
 )
 
 // ApplyLexicographicSortingGadget Add sorting constraints for a sequence of one
@@ -33,19 +34,19 @@ func ApplyLexicographicSortingGadget(columns []uint, signs []bool, bitwidth uint
 		panic("Inconsistent number of columns and signs for lexicographic sort.")
 	}
 	// Determine enclosing module for this gadget.
-	module, multiplier := sc.DetermineEnclosingModuleOfColumns(columns, schema)
+	ctx := sc.ContextOfColumns(columns, schema)
 	// Construct a unique prefix for this sort.
 	prefix := constructLexicographicSortingPrefix(columns, signs, schema)
 	// Add trace computation
 	deltaIndex := schema.AddAssignment(
-		assignment.NewLexicographicSort(prefix, module, multiplier, columns, signs, bitwidth))
+		assignment.NewLexicographicSort(prefix, ctx, columns, signs, bitwidth))
 	// Construct selecto bits.
-	addLexicographicSelectorBits(prefix, module, multiplier, deltaIndex, columns, schema)
+	addLexicographicSelectorBits(prefix, ctx, deltaIndex, columns, schema)
 	// Construct delta terms
 	constraint := constructLexicographicDeltaConstraint(deltaIndex, columns, signs)
 	// Add delta constraint
 	deltaName := fmt.Sprintf("%s:delta", prefix)
-	schema.AddVanishingConstraint(deltaName, module, multiplier, nil, constraint)
+	schema.AddVanishingConstraint(deltaName, ctx, nil, constraint)
 	// Add necessary bitwidth constraints
 	ApplyBitwidthGadget(deltaIndex, bitwidth, schema)
 }
@@ -77,7 +78,7 @@ func constructLexicographicSortingPrefix(columns []uint, signs []bool, schema *a
 //
 // NOTE: this implementation differs from the original corset which used an
 // additional "Eq" bit to help ensure at most one selector bit was enabled.
-func addLexicographicSelectorBits(prefix string, module uint, multiplier uint,
+func addLexicographicSelectorBits(prefix string, context trace.Context,
 	deltaIndex uint, columns []uint, schema *air.Schema) {
 	ncols := uint(len(columns))
 	// Calculate column index of first selector bit
@@ -102,7 +103,7 @@ func addLexicographicSelectorBits(prefix string, module uint, multiplier uint,
 		pterms[i] = air.NewColumnAccess(bitIndex+i, 0)
 		pDiff := air.NewColumnAccess(columns[i], 0).Sub(air.NewColumnAccess(columns[i], -1))
 		pName := fmt.Sprintf("%s:%d:a", prefix, i)
-		schema.AddVanishingConstraint(pName, module, multiplier,
+		schema.AddVanishingConstraint(pName, context,
 			nil, air.NewConst64(1).Sub(&air.Add{Args: pterms}).Mul(pDiff))
 		// (∀j<i.Bj=0) ∧ Bi=1 ==> C[k]≠C[k-1]
 		qDiff := Normalise(air.NewColumnAccess(columns[i], 0).Sub(air.NewColumnAccess(columns[i], -1)), schema)
@@ -115,14 +116,14 @@ func addLexicographicSelectorBits(prefix string, module uint, multiplier uint,
 			constraint = air.NewConst64(1).Sub(&air.Add{Args: qterms}).Mul(constraint)
 		}
 
-		schema.AddVanishingConstraint(qName, module, multiplier, nil, constraint)
+		schema.AddVanishingConstraint(qName, context, nil, constraint)
 	}
 
 	sum := &air.Add{Args: terms}
 	// (sum = 0) ∨ (sum = 1)
 	constraint := sum.Mul(sum.Equate(air.NewConst64(1)))
 	name := fmt.Sprintf("%s:xor", prefix)
-	schema.AddVanishingConstraint(name, module, multiplier, nil, constraint)
+	schema.AddVanishingConstraint(name, context, nil, constraint)
 }
 
 // Construct the lexicographic delta constraint.  This states that the delta

pkg/air/gadgets/normalisation.go

@@ -29,17 +29,17 @@ func Normalise(e air.Expr, schema *air.Schema) air.Expr {
 // ensure it really holds the inverted value.
 func ApplyPseudoInverseGadget(e air.Expr, schema *air.Schema) air.Expr {
 	// Determine enclosing module.
-	module, multiplier := sc.DetermineEnclosingModuleOfExpression(e, schema)
+	ctx := e.Context(schema)
 	// Construct inverse computation
 	ie := &Inverse{Expr: e}
 	// Determine computed column name
 	name := ie.String()
 	// Look up column
-	index, ok := sc.ColumnIndexOf(schema, module, name)
+	index, ok := sc.ColumnIndexOf(schema, ctx.Module(), name)
 	// Add new column (if it does not already exist)
 	if !ok {
 		// Add computed column
-		index = schema.AddAssignment(assignment.NewComputedColumn(module, name, multiplier, ie))
+		index = schema.AddAssignment(assignment.NewComputedColumn(ctx, name, ie))
 	}
 
 	// Construct 1/e
@@ -54,10 +54,10 @@ func ApplyPseudoInverseGadget(e air.Expr, schema *air.Schema) air.Expr {
 	inv_e_implies_one_e_e := inv_e.Mul(one_e_e)
 	// Ensure (e != 0) ==> (1 == e/e)
 	l_name := fmt.Sprintf("[%s <=]", ie.String())
-	schema.AddVanishingConstraint(l_name, module, multiplier, nil, e_implies_one_e_e)
+	schema.AddVanishingConstraint(l_name, ctx, nil, e_implies_one_e_e)
 	// Ensure (e/e != 0) ==> (1 == e/e)
 	r_name := fmt.Sprintf("[%s =>]", ie.String())
-	schema.AddVanishingConstraint(r_name, module, multiplier, nil, inv_e_implies_one_e_e)
+	schema.AddVanishingConstraint(r_name, ctx, nil, inv_e_implies_one_e_e)
 	// Done
 	return air.NewColumnAccess(index, 0)
 }
@@ -81,7 +81,7 @@ func (e *Inverse) Bounds() util.Bounds { return e.Expr.Bounds() }
 
 // Context determines the evaluation context (i.e. enclosing module) for this
 // expression.
-func (e *Inverse) Context(schema sc.Schema) (uint, uint, bool) {
+func (e *Inverse) Context(schema sc.Schema) tr.Context {
 	return e.Expr.Context(schema)
 }
 

pkg/air/schema.go

@@ -7,6 +7,7 @@ import (
 	"github.com/consensys/go-corset/pkg/schema"
 	"github.com/consensys/go-corset/pkg/schema/assignment"
 	"github.com/consensys/go-corset/pkg/schema/constraint"
+	"github.com/consensys/go-corset/pkg/trace"
 	"github.com/consensys/go-corset/pkg/util"
 )
 
@@ -64,14 +65,14 @@ func (p *Schema) AddModule(name string) uint {
 
 // AddColumn appends a new data column whose values must be provided by the
 // user.
-func (p *Schema) AddColumn(module uint, name string, datatype schema.Type) uint {
-	if module >= uint(len(p.modules)) {
-		panic(fmt.Sprintf("invalid module index (%d)", module))
+func (p *Schema) AddColumn(context trace.Context, name string, datatype schema.Type) uint {
+	if context.Module() >= uint(len(p.modules)) {
+		panic(fmt.Sprintf("invalid module index (%d)", context.Module()))
 	}
 
 	// NOTE: the air level has no ability to enforce the type specified for a
 	// given column.
-	p.inputs = append(p.inputs, assignment.NewDataColumn(module, name, datatype))
+	p.inputs = append(p.inputs, assignment.NewDataColumn(context, name, datatype))
 	// Calculate column index
 	return uint(len(p.inputs) - 1)
 }
@@ -87,8 +88,8 @@ func (p *Schema) AddAssignment(c schema.Assignment) uint {
 }
 
 // AddLookupConstraint appends a new lookup constraint.
-func (p *Schema) AddLookupConstraint(handle string, source uint, source_multiplier uint,
-	target uint, target_multiplier uint, sources []uint, targets []uint) {
+func (p *Schema) AddLookupConstraint(handle string, source trace.Context,
+	target trace.Context, sources []uint, targets []uint) {
 	if len(targets) != len(sources) {
 		panic("differeng number of target / source lookup columns")
 	}
@@ -103,7 +104,7 @@ func (p *Schema) AddLookupConstraint(handle string, source uint, source_multipli
 	}
 	//
 	p.constraints = append(p.constraints,
-		constraint.NewLookupConstraint(handle, source, source_multiplier, target, target_multiplier, from, into))
+		constraint.NewLookupConstraint(handle, source, target, from, into))
 }
 
 // AddPermutationConstraint appends a new permutation constraint which
@@ -114,13 +115,13 @@ func (p *Schema) AddPermutationConstraint(targets []uint, sources []uint) {
 }
 
 // AddVanishingConstraint appends a new vanishing constraint.
-func (p *Schema) AddVanishingConstraint(handle string, module uint, multiplier uint, domain *int, expr Expr) {
-	if module >= uint(len(p.modules)) {
-		panic(fmt.Sprintf("invalid module index (%d)", module))
+func (p *Schema) AddVanishingConstraint(handle string, context trace.Context, domain *int, expr Expr) {
+	if context.Module() >= uint(len(p.modules)) {
+		panic(fmt.Sprintf("invalid module index (%d)", context.Module()))
 	}
 	// TODO: sanity check expression enclosed by module
 	p.constraints = append(p.constraints,
-		constraint.NewVanishingConstraint(handle, module, multiplier, domain, constraint.ZeroTest[Expr]{Expr: expr}))
+		constraint.NewVanishingConstraint(handle, context, domain, constraint.ZeroTest[Expr]{Expr: expr}))
 }
 
 // AddRangeConstraint appends a new range constraint.

pkg/binfile/computation.go

@@ -6,6 +6,7 @@ import (
 	"github.com/consensys/go-corset/pkg/hir"
 	sc "github.com/consensys/go-corset/pkg/schema"
 	"github.com/consensys/go-corset/pkg/schema/assignment"
+	"github.com/consensys/go-corset/pkg/trace"
 )
 
 type jsonComputationSet struct {
@@ -27,7 +28,6 @@ type jsonSortedComputation struct {
 // =============================================================================
 
 func (e jsonComputationSet) addToSchema(schema *hir.Schema) {
-	var multiplier uint
 	//
 	for _, c := range e.Computations {
 		if c.Sorted != nil {
@@ -44,6 +44,8 @@ func (e jsonComputationSet) addToSchema(schema *hir.Schema) {
 			// Convert target refs into columns
 			targets := make([]sc.Column, len(targetRefs))
 			//
+			ctx := trace.VoidContext()
+			//
 			for i, targetRef := range targetRefs {
 				src_cid, src_mid := sourceRefs[i].resolve(schema)
 				_, dst_mid := targetRef.resolve(schema)
@@ -53,20 +55,21 @@ func (e jsonComputationSet) addToSchema(schema *hir.Schema) {
 				}
 				// Determine type of source column
 				ith := schema.Columns().Nth(src_cid)
+				ctx = ctx.Join(ith.Context())
 				// Sanity check we have a sensible type here.
 				if ith.Type().AsUint() == nil {
 					panic(fmt.Sprintf("source column %s has field type", sourceRefs[i]))
-				} else if i == 0 {
-					multiplier = ith.LengthMultiplier()
-				} else if multiplier != ith.LengthMultiplier() {
-					panic(fmt.Sprintf("source column %s has inconsistent length multiplier", sourceRefs[i]))
+				} else if ctx.IsConflicted() {
+					panic(fmt.Sprintf("source column %s has conflicted evaluation context", sourceRefs[i]))
+				} else if ctx.IsVoid() {
+					panic(fmt.Sprintf("source column %s has void evaluation context", sourceRefs[i]))
 				}
 
 				sources[i] = src_cid
-				targets[i] = sc.NewColumn(ith.Module(), targetRef.column, multiplier, ith.Type())
+				targets[i] = sc.NewColumn(ctx, targetRef.column, ith.Type())
 			}
 			// Finally, add the sorted permutation assignment
-			schema.AddAssignment(assignment.NewSortedPermutation(module, multiplier, targets, c.Sorted.Signs, sources))
+			schema.AddAssignment(assignment.NewSortedPermutation(ctx, targets, c.Sorted.Signs, sources))
 		}
 	}
 }