kaizen: Increase throughput with flexible FA traversal (#332)

* kaizen: Increase throughput with flexible FA traversal

Signed-off-by: Tim Bray <[email protected]>

* don't fail benchmark on alert

Signed-off-by: Tim Bray <[email protected]>

---------

Signed-off-by: Tim Bray <[email protected]>

.github/workflows/benchmarks.yml

@@ -52,7 +52,7 @@ jobs:
 
           # Alert on regression
           alert-threshold: "120%"
-          fail-on-alert: true
+          fail-on-alert: false
           comment-on-alert: false
 
           # Disable github pages, for now.

match_set.go

@@ -34,11 +34,6 @@ func (m *matchSet) addXSingleThreaded(exes ...X) *matchSet {
 	return m
 }
 
-func (m *matchSet) contains(x X) bool {
-	_, ok := m.set[x]
-	return ok
-}
-
 func (m *matchSet) matches() []X {
 	matches := make([]X, 0, len(m.set))
 	for x := range m.set {

match_set_test.go

@@ -51,6 +51,11 @@ func TestAddXSingleThreaded(t *testing.T) {
 	}
 }
 
+func (m *matchSet) contains(x X) bool {
+	_, ok := m.set[x]
+	return ok
+}
+
 func isSameMatches(matchSet *matchSet, exes ...X) bool {
 	if len(exes) == 0 && len(matchSet.matches()) == 0 {
 		return true

nfa.go

@@ -39,7 +39,29 @@ func (tm *transmap) all() []*fieldMatcher {
 	return all
 }
 
-func traverseFA(table *smallTable, val []byte, transitions []*fieldMatcher, bufs *bufpair) []*fieldMatcher {
+// While some Quamina patterns require the use of NFAs, many (most?) don't, and while we're still using a
+// NFA-capable data structure, we can traverse it deterministically if we know in advance that every
+// combination of an faState with a byte will transition to at most one other faState.
+
+func traverseDFA(table *smallTable, val []byte, transitions []*fieldMatcher) []*fieldMatcher {
+	for index := 0; index <= len(val); index++ {
+		var utf8Byte byte
+		if index < len(val) {
+			utf8Byte = val[index]
+		} else {
+			utf8Byte = valueTerminator
+		}
+		next := table.dStep(utf8Byte)
+		if next == nil {
+			break
+		}
+		transitions = append(transitions, next.fieldTransitions...)
+		table = next.table
+	}
+	return transitions
+}
+
+func traverseNFA(table *smallTable, val []byte, transitions []*fieldMatcher, bufs *bufpair) []*fieldMatcher {
 	currentStates := bufs.buf1
 	currentStates = append(currentStates, &faState{table: table})
 	nextStates := bufs.buf2

shell_style_test.go

@@ -65,14 +65,14 @@ func TestMakeShellStyleFA(t *testing.T) {
 		var bufs bufpair
 		for _, should := range shouldsForPatterns[i] {
 			var transitions []*fieldMatcher
-			gotTrans := traverseFA(a, []byte(should), transitions, &bufs)
+			gotTrans := traverseNFA(a, []byte(should), transitions, &bufs)
 			if len(gotTrans) != 1 || gotTrans[0] != wanted {
 				t.Errorf("Failure for %s on %s", pattern, should)
 			}
 		}
 		for _, shouldNot := range shouldNotForPatterns[i] {
 			var transitions []*fieldMatcher
-			gotTrans := traverseFA(a, []byte(shouldNot), transitions, &bufs)
+			gotTrans := traverseNFA(a, []byte(shouldNot), transitions, &bufs)
 			if gotTrans != nil {
 				t.Errorf("bogus match for %s on %s", pattern, shouldNot)
 			}

small_table.go

@@ -73,6 +73,22 @@ func (t *smallTable) step(utf8Byte byte, out *stepOut) {
 	panic("Malformed smallTable")
 }
 
+// dStep takes a step through an NFA in the case where it is known that the NFA in question
+// is deterministic, i.e. each combination of an faState and a byte value transitions to at
+// most one other byte value.
+func (t *smallTable) dStep(utf8Byte byte) *faState {
+	for index, ceiling := range t.ceilings {
+		if utf8Byte < ceiling {
+			if t.steps[index] == nil {
+				return nil
+			} else {
+				return t.steps[index].states[0]
+			}
+		}
+	}
+	panic("Malformed smallTable")
+}
+
 // makeSmallTable creates a pre-loaded small table, with all bytes not otherwise specified having the defaultStep
 // value, and then a few other values with their indexes and values specified in the other two arguments. The
 // goal is to reduce memory churn

value_matcher.go

@@ -30,6 +30,7 @@ type vmFields struct {
 	singletonMatch      []byte
 	singletonTransition *fieldMatcher
 	hasQNumbers         bool
+	isNondeterministic  bool
 }
 
 func (m *valueMatcher) fields() *vmFields {
@@ -71,14 +72,22 @@ func (m *valueMatcher) transitionOn(eventField *Field, bufs *bufpair) []*fieldMa
 	case vmFields.startTable != nil:
 		// if there is a potential for a numeric match, try making a Q number from the event
 		if vmFields.hasQNumbers && eventField.IsQNumber {
-			qNumber, err := qNumFromBytes(val)
+			qNum, err := qNumFromBytes(val)
 			if err == nil {
-				return traverseFA(vmFields.startTable, qNumber, transitions, bufs)
+				if vmFields.isNondeterministic {
+					return traverseNFA(vmFields.startTable, qNum, transitions, bufs)
+				} else {
+					return traverseDFA(vmFields.startTable, qNum, transitions)
+				}
 			}
 		}
 
 		// if it doesn't work as a Q number for some reason, go ahead and compare the string values
-		return traverseFA(vmFields.startTable, val, transitions, bufs)
+		if vmFields.isNondeterministic {
+			return traverseNFA(vmFields.startTable, val, transitions, bufs)
+		} else {
+			return traverseDFA(vmFields.startTable, val, transitions)
+		}
 
 	default:
 		// no FA, no singleton, nothing to do, this probably can't happen because a flattener
@@ -108,6 +117,7 @@ func (m *valueMatcher) addTransition(val typedVal, printer printer) *fieldMatche
 			newFA, nextField = makeMultiAnythingButFA(val.list)
 		case shellStyleType:
 			newFA, nextField = makeShellStyleFA(valBytes, printer)
+			fields.isNondeterministic = true
 		case prefixType:
 			newFA, nextField = makePrefixFA(valBytes)
 		default:
@@ -150,6 +160,7 @@ func (m *valueMatcher) addTransition(val typedVal, printer printer) *fieldMatche
 		case shellStyleType:
 			newAutomaton, nextField := makeShellStyleFA(valBytes, printer)
 			fields.startTable = newAutomaton
+			fields.isNondeterministic = true
 			m.update(fields)
 			return nextField
 		case prefixType:
@@ -187,6 +198,7 @@ func (m *valueMatcher) addTransition(val typedVal, printer printer) *fieldMatche
 		newFA, nextField = makeMultiAnythingButFA(val.list)
 	case shellStyleType:
 		newFA, nextField = makeShellStyleFA(valBytes, printer)
+		fields.isNondeterministic = true
 	case prefixType:
 		newFA, nextField = makePrefixFA(valBytes)
 	default: