feat: remove offset shifts in plonk compile

frontend/compile.go

@@ -88,7 +88,7 @@ func parseCircuit(builder Builder, circuit Circuit) (err error) {
 	}
 	// recursively parse through reflection the circuits members to find all Constraints that need to be allocated
 	// (secret or public inputs)
-	s, err = schema.Parse(circuit, tVariable, handler)
+	_, err = schema.Parse(circuit, tVariable, handler)
 	if err != nil {
 		return err
 	}

frontend/cs/scs/builder.go

@@ -105,7 +105,7 @@ func (system *scs) addPlonkConstraint(l, r, o compiled.Term, cidl, cidr, cidm1,
 // newInternalVariable creates a new wire, appends it on the list of wires of the circuit, sets
 // the wire's id to the number of wires, and returns it
 func (system *scs) newInternalVariable() compiled.Term {
-	idx := system.NbInternalVariables
+	idx := system.NbInternalVariables + system.NbPublicVariables + system.NbSecretVariables
 	system.NbInternalVariables++
 	return compiled.Pack(idx, compiled.CoeffIdOne, schema.Internal)
 }
@@ -119,7 +119,7 @@ func (system *scs) AddPublicVariable(name string) frontend.Variable {
 
 // AddSecretVariable creates a new Secret Variable
 func (system *scs) AddSecretVariable(name string) frontend.Variable {
-	idx := len(system.Secret)
+	idx := len(system.Secret) + system.NbPublicVariables
 	system.Secret = append(system.Secret, name)
 	return compiled.Pack(idx, compiled.CoeffIdOne, schema.Secret)
 }
@@ -217,14 +217,19 @@ func (system *scs) checkVariables() error {
 					cptPublic--
 				}
 			case schema.Secret:
+				vID -= system.NbPublicVariables
 				if !secretConstrained[vID] {
 					secretConstrained[vID] = true
 					cptSecret--
 				}
 			case schema.Internal:
-				if _, ok := system.MHints[vID]; !mHintsConstrained[vID] && ok {
-					mHintsConstrained[vID] = true
-					cptHints--
+				if _, ok := system.MHints[vID]; ok {
+					vID -= (system.NbPublicVariables + system.NbSecretVariables)
+					if !mHintsConstrained[vID] {
+						mHintsConstrained[vID] = true
+						cptHints--
+					}
+
 				}
 			}
 		}
@@ -301,86 +306,13 @@ func (cs *scs) Compile() (frontend.CompiledConstraintSystem, error) {
 		ConstraintSystem: cs.ConstraintSystem,
 		Constraints:      cs.Constraints,
 	}
-	res.NbPublicVariables = len(cs.Public)
-	res.NbSecretVariables = len(cs.Secret)
-
-	// Logs, DebugInfo and hints are copied, the only thing that will change
-	// is that ID of the wires will be offseted to take into account the final wire vector ordering
-	// that is: public wires  | secret wires | internal wires
-
-	// shift variable ID
-	// we want publicWires | privateWires | internalWires
-	shiftVID := func(oldID int, visibility schema.Visibility) int {
-		switch visibility {
-		case schema.Internal:
-			return oldID + res.NbPublicVariables + res.NbSecretVariables
-		case schema.Public:
-			return oldID
-		case schema.Secret:
-			return oldID + res.NbPublicVariables
-		default:
-			return oldID
-		}
-	}
-
-	offsetTermID := func(t *compiled.Term) {
-		_, VID, visibility := t.Unpack()
-		t.SetWireID(shiftVID(VID, visibility))
-	}
-
-	// offset the IDs of all constraints so that the variables are
-	// numbered like this: [publicVariables | secretVariables | internalVariables ]
-	for i := 0; i < len(res.Constraints); i++ {
-		r1c := &res.Constraints[i]
-		offsetTermID(&r1c.L)
-		offsetTermID(&r1c.R)
-		offsetTermID(&r1c.O)
-		offsetTermID(&r1c.M[0])
-		offsetTermID(&r1c.M[1])
-	}
-
-	// we need to offset the ids in Logs & DebugInfo
-	for i := 0; i < len(cs.Logs); i++ {
-		for j := 0; j < len(res.Logs[i].ToResolve); j++ {
-			offsetTermID(&res.Logs[i].ToResolve[j])
-		}
+	// sanity check
+	if res.NbPublicVariables != len(cs.Public) || res.NbPublicVariables != cs.Schema.NbPublic {
+		panic("number of public variables is inconsitent") // it grew after the schema parsing?
 	}
-	for i := 0; i < len(cs.DebugInfo); i++ {
-		for j := 0; j < len(res.DebugInfo[i].ToResolve); j++ {
-			offsetTermID(&res.DebugInfo[i].ToResolve[j])
-		}
-	}
-
-	// we need to offset the ids in the hints
-	shiftedMap := make(map[int]*compiled.Hint)
-HINTLOOP:
-	for _, hint := range cs.MHints {
-		ws := make([]int, len(hint.Wires))
-		// we set for all outputs in shiftedMap. If one shifted output
-		// is in shiftedMap, then all are
-		for i, vID := range hint.Wires {
-			ws[i] = shiftVID(vID, schema.Internal)
-			if _, ok := shiftedMap[ws[i]]; i == 0 && ok {
-				continue HINTLOOP
-			}
-		}
-		inputs := make([]interface{}, len(hint.Inputs))
-		copy(inputs, hint.Inputs)
-		for j := 0; j < len(inputs); j++ {
-			switch t := inputs[j].(type) {
-			case compiled.Term:
-				offsetTermID(&t)
-				inputs[j] = t // TODO check if we can remove it
-			default:
-				inputs[j] = t
-			}
-		}
-		ch := &compiled.Hint{ID: hint.ID, Inputs: inputs, Wires: ws}
-		for _, vID := range ws {
-			shiftedMap[vID] = ch
-		}
+	if res.NbSecretVariables != len(cs.Secret) || res.NbSecretVariables != cs.Schema.NbSecret {
+		panic("number of secret variables is inconsitent") // it grew after the schema parsing?
 	}
-	res.MHints = shiftedMap
 
 	// build levels
 	res.Levels = buildLevels(res)
@@ -409,6 +341,8 @@ func (cs *scs) SetSchema(s *schema.Schema) {
 		panic("SetSchema called multiple times")
 	}
 	cs.Schema = s
+	cs.NbPublicVariables = s.NbPublic
+	cs.NbSecretVariables = s.NbSecret
 }
 
 func buildLevels(ccs compiled.SparseR1CS) [][]int {