Analyzing circuits.

apps/garbled/main.go

@@ -1,7 +1,7 @@
 //
 // main.go
 //
-// Copyright (c) 2019-2021 Markku Rossi
+// Copyright (c) 2019-2022 Markku Rossi
 //
 // All rights reserved.
 //
@@ -69,6 +69,7 @@ func main() {
 	bmr := flag.Int("bmr", -1, "semi-honest secure BMR protocol player number")
 	doc := flag.String("doc", "",
 		"generate documentation about argument files")
+	analyze := flag.Bool("analyze", false, "analyze circuits")
 	flag.Parse()
 
 	log.SetFlags(0)
@@ -102,6 +103,7 @@ func main() {
 	if *ssa && !*compile {
 		params.NoCircCompile = true
 	}
+	params.CircAnalyze = *analyze
 
 	if len(*doc) > 0 {
 		doc, err := NewHTMLDoc(*doc)
@@ -194,8 +196,15 @@ func main() {
 		}
 	}
 
-	if verbose && circ != nil {
-		fmt.Printf("Circuit: %v\n", circ)
+	if circ != nil {
+		circ.AssignLevels()
+
+		if params.CircAnalyze {
+			circ.Analyze()
+		}
+		if verbose {
+			fmt.Printf("Circuit: %v\n", circ)
+		}
 	}
 
 	if *ssa || *compile || *stream {

circuit/analyze.go

@@ -0,0 +1,42 @@
+//
+// Copyright (c) 2021 Markku Rossi
+//
+// All rights reserved.
+//
+
+package circuit
+
+import (
+	"fmt"
+)
+
+// Analyze identifies potential optimizations for the circuit.
+func (c *Circuit) Analyze() {
+	fmt.Printf("analyzing circuit %v\n", c)
+
+	from := make([][]Gate, c.NumWires)
+	to := make([][]Gate, c.NumWires)
+
+	// Collect wire inputs and outputs.
+	for _, g := range c.Gates {
+		switch g.Op {
+		case XOR, XNOR, AND, OR:
+			to[g.Input1] = append(to[g.Input1], g)
+			fallthrough
+
+		case INV:
+			to[g.Input0] = append(to[g.Input0], g)
+			from[g.Output] = append(to[g.Output], g)
+		}
+	}
+
+	// INV gates as single output of input gate.
+	for _, g := range c.Gates {
+		if g.Op != INV {
+			continue
+		}
+		if len(to[g.Input0]) == 1 && len(from[g.Input0]) == 1 {
+			fmt.Printf("%v -> %v\n", from[g.Input0][0].Op, g.Op)
+		}
+	}
+}

circuit/circuit.go

@@ -1,5 +1,5 @@
 //
-// Copyright (c) 2019-2021 Markku Rossi
+// Copyright (c) 2019-2022 Markku Rossi
 //
 // All rights reserved.
 //
@@ -28,17 +28,25 @@ const (
 	OR
 	INV
 	Count
+	NumLevels
+	MaxWidth
 )
 
 // Stats holds statistics about circuit operations.
-type Stats [Count + 1]uint64
+type Stats [MaxWidth + 1]uint64
 
 // Add adds the argument statistics to this statistics object.
 func (stats *Stats) Add(o Stats) {
 	for i := XOR; i < Count; i++ {
 		stats[i] += o[i]
 	}
 	stats[Count]++
+
+	for i := NumLevels; i <= MaxWidth; i++ {
+		if o[i] > stats[i] {
+			stats[i] = o[i]
+		}
+	}
 }
 
 // Count returns the number of gates in the statistics object.
@@ -67,6 +75,8 @@ func (stats Stats) String() string {
 	}
 	result += fmt.Sprintf(" xor=%d", stats[XOR]+stats[XNOR])
 	result += fmt.Sprintf(" !xor=%d", stats[AND]+stats[OR]+stats[INV])
+	result += fmt.Sprintf(" levels=%d", stats[NumLevels])
+	result += fmt.Sprintf(" width=%d", stats[MaxWidth])
 	return result
 }
 
@@ -336,12 +346,59 @@ func (c *Circuit) Dump() {
 	}
 }
 
+// AssignLevels assigns levels for gates. The level desribes how many
+// steps away the gate is from input wires.
+func (c *Circuit) AssignLevels() {
+	levels := make([]Level, c.NumWires)
+	countByLevel := make([]uint32, c.NumWires)
+
+	var max Level
+
+	for _, gate := range c.Gates {
+		level := levels[gate.Input0]
+		if gate.Op != INV {
+			l1 := levels[gate.Input1]
+			if l1 > level {
+				level = l1
+			}
+		}
+		gate.Level = level
+		countByLevel[level]++
+
+		level++
+
+		levels[gate.Output] = level
+		if level > max {
+			max = level
+		}
+	}
+	c.Stats[NumLevels] = uint64(max)
+
+	var maxWidth uint32
+	for _, count := range countByLevel {
+		if count > maxWidth {
+			maxWidth = count
+		}
+	}
+	if false {
+		for i := 0; i < int(max); i++ {
+			fmt.Printf("%v,%v\n", i, countByLevel[i])
+		}
+	}
+
+	c.Stats[MaxWidth] = uint64(maxWidth)
+}
+
+// Level defines gate's distance from input wires.
+type Level uint32
+
 // Gate specifies a boolean gate.
 type Gate struct {
 	Input0 Wire
 	Input1 Wire
 	Output Wire
 	Op     Operation
+	Level  Level
 }
 
 func (g Gate) String() string {

circuit/circuit_test.go

@@ -0,0 +1,18 @@
+//
+// Copyright (c) 2022 Markku Rossi
+//
+// All rights reserved.
+//
+
+package circuit
+
+import (
+	"fmt"
+	"testing"
+	"unsafe"
+)
+
+func TestSize(t *testing.T) {
+	var g Gate
+	fmt.Printf("sizeof(Gate)=%d\n", unsafe.Sizeof(g))
+}

compiler/ast/builtin.go

@@ -1,5 +1,5 @@
 //
-// Copyright (c) 2019-2021 Markku Rossi
+// Copyright (c) 2019-2022 Markku Rossi
 //
 // All rights reserved.
 //
@@ -368,6 +368,8 @@ func nativeCircuit(name string, block *ssa.Block, ctx *Codegen,
 		}
 	}
 
+	circ.AssignLevels()
+
 	if ctx.Verbose {
 		fmt.Printf(" - native %s: %v\n", name, circ)
 	}

compiler/ssa/circuitgen.go

@@ -1,5 +1,5 @@
 //
-// Copyright (c) 2020-2021 Markku Rossi
+// Copyright (c) 2020-2022 Markku Rossi
 //
 // All rights reserved.
 //

compiler/ssa/streamer.go

@@ -1,5 +1,5 @@
 //
-// Copyright (c) 2020-2021 Markku Rossi
+// Copyright (c) 2020-2022 Markku Rossi
 //
 // All rights reserved.
 //
@@ -517,6 +517,7 @@ func (prog *Program) StreamCircuit(conn *p2p.Conn, params *utils.Params,
 				if params.Verbose && circuit.StreamDebug {
 					fmt.Printf("%05d: - %s\n", idx, circ)
 				}
+				circ.AssignLevels()
 			}
 			if false {
 				circ.Dump()
@@ -594,7 +595,7 @@ func (prog *Program) StreamCircuit(conn *p2p.Conn, params *utils.Params,
 		prog.numWires)
 
 	if params.Diagnostics {
-		tab := tabulate.New(tabulate.CompactUnicode)
+		tab := tabulate.New(tabulate.CompactUnicodeLight)
 		tab.Header("Instr").SetAlign(tabulate.ML)
 		tab.Header("Count").SetAlign(tabulate.MR)
 		tab.Header("XOR").SetAlign(tabulate.MR)
@@ -603,6 +604,8 @@ func (prog *Program) StreamCircuit(conn *p2p.Conn, params *utils.Params,
 		tab.Header("OR").SetAlign(tabulate.MR)
 		tab.Header("INV").SetAlign(tabulate.MR)
 		tab.Header("!XOR").SetAlign(tabulate.MR)
+		tab.Header("L").SetAlign(tabulate.MR)
+		tab.Header("W").SetAlign(tabulate.MR)
 
 		var keys []string
 		for k := range istats {
@@ -626,6 +629,8 @@ func (prog *Program) StreamCircuit(conn *p2p.Conn, params *utils.Params,
 				row.Column(fmt.Sprintf("%d", stats[circuit.INV]))
 				row.Column(fmt.Sprintf("%d",
 					stats[circuit.OR]+stats[circuit.AND]+stats[circuit.INV]))
+				row.Column(fmt.Sprintf("%d", stats[circuit.NumLevels]))
+				row.Column(fmt.Sprintf("%d", stats[circuit.MaxWidth]))
 			}
 		}
 		tab.Print(os.Stdout)

compiler/utils/params.go

@@ -27,6 +27,7 @@ type Params struct {
 	CircOut       io.WriteCloser
 	CircDotOut    io.WriteCloser
 	CircFormat    string
+	CircAnalyze   bool
 
 	CircMultArrayTreshold int