Improve mutation API in Fuzzing Platform (#2296)

Author: Markoutte

utbot-fuzzing/src/main/kotlin/org/utbot/fuzzing/Api.kt

@@ -37,17 +37,22 @@ data class Configuration(
     /**
      * Probability of creating shifted array values instead of generating new values for modification.
      */
-    var probCollectionMutationInsteadCreateNew: Int = 50,
+    var probCollectionDuplicationInsteadCreateNew: Int = 10,
+
+    /**
+     * Probability of creating empty collections
+     */
+    var probEmptyCollectionCreation: Int = 1,
 
     /**
      * Probability to prefer change constructor instead of modification.
      */
-    var probConstructorMutationInsteadModificationMutation: Int = 90,
+    var probConstructorMutationInsteadModificationMutation: Int = 30,
 
     /**
-     * Probability to shuffle modification list of the recursive object
+     * Probability to a shuffle modification list of the recursive object
      */
-    var probShuffleAndCutRecursiveObjectModificationMutation: Int = 10,
+    var probShuffleAndCutRecursiveObjectModificationMutation: Int = 30,
 
     /**
      * Probability to prefer create rectangle collections instead of creating saw-like one.
@@ -62,17 +67,7 @@ data class Configuration(
     /**
      * When mutating StringValue a new string will not exceed this value.
      */
-    var maxStringLengthWhenMutated: Int = 64,
-
-    /**
-     * Probability of adding a new character when mutating StringValue
-     */
-    var probStringAddCharacter: Int = 50,
-
-    /**
-     * Probability of removing an old character from StringValue when mutating
-     */
-    var probStringRemoveCharacter: Int = 50,
+    var maxStringLengthWhenMutated: Int = 128,
 
     /**
      * Probability of reusing same generated value when 2 or more parameters have the same type.

utbot-fuzzing/src/main/kotlin/org/utbot/fuzzing/Configuration.kt

@@ -4,8 +4,105 @@ package org.utbot.fuzzing
 
 import org.utbot.fuzzing.seeds.BitVectorValue
 import org.utbot.fuzzing.seeds.IEEE754Value
+import org.utbot.fuzzing.seeds.KnownValue
+import org.utbot.fuzzing.seeds.StringValue
+import org.utbot.fuzzing.utils.chooseOne
+import org.utbot.fuzzing.utils.flipCoin
 import kotlin.random.Random
 
+class MutationFactory<TYPE, RESULT> {
+
+    fun mutate(node: Node<TYPE, RESULT>, random: Random, configuration: Configuration): Node<TYPE, RESULT> {
+        if (node.result.isEmpty()) return node
+        val indexOfMutatedResult = random.chooseOne(node.result.map(::rate).toDoubleArray())
+        val recursive: NodeMutation<TYPE, RESULT> = NodeMutation { n, r, c ->
+            mutate(n, r, c)
+        }
+        val mutated = when (val resultToMutate = node.result[indexOfMutatedResult]) {
+            is Result.Simple<TYPE, RESULT> -> Result.Simple(resultToMutate.mutation(resultToMutate.result, random), resultToMutate.mutation)
+            is Result.Known<TYPE, RESULT, *> -> {
+                val mutations = resultToMutate.value.mutations()
+                if (mutations.isNotEmpty()) {
+                    resultToMutate.mutate(mutations.random(random), random, configuration)
+                } else {
+                    resultToMutate
+                }
+            }
+            is Result.Recursive<TYPE, RESULT> -> {
+                when {
+                    resultToMutate.modify.isEmpty() || random.flipCoin(configuration.probConstructorMutationInsteadModificationMutation) ->
+                        RecursiveMutations.Constructor<TYPE, RESULT>()
+                    random.flipCoin(configuration.probShuffleAndCutRecursiveObjectModificationMutation) ->
+                        RecursiveMutations.ShuffleAndCutModifications()
+                    else ->
+                        RecursiveMutations.Mutate()
+                }.mutate(resultToMutate, recursive, random, configuration)
+            }
+            is Result.Collection<TYPE, RESULT> -> if (resultToMutate.modify.isNotEmpty()) {
+                when {
+                    random.flipCoin(100 - configuration.probCollectionShuffleInsteadResultMutation) ->
+                        CollectionMutations.Mutate()
+                    else ->
+                        CollectionMutations.Shuffle<TYPE, RESULT>()
+                }.mutate(resultToMutate, recursive, random, configuration)
+            } else {
+                resultToMutate
+            }
+            is Result.Empty -> resultToMutate
+        }
+        return Node(node.result.toMutableList().apply {
+            set(indexOfMutatedResult, mutated)
+        }, node.parameters, node.builder)
+    }
+
+    /**
+     * Rates somehow the result.
+     *
+     * For example, fuzzing should not try to mutate some empty structures, like empty collections or objects.
+     */
+    private fun <TYPE, RESULT> rate(result: Result<TYPE, RESULT>): Double {
+        if (!canMutate(result)) {
+            return ALMOST_ZERO
+        }
+        return when (result) {
+            is Result.Recursive<TYPE, RESULT> -> if (result.construct.parameters.isEmpty() and result.modify.isEmpty()) ALMOST_ZERO else 0.5
+            is Result.Collection<TYPE, RESULT> -> if (result.iterations == 0) return ALMOST_ZERO else 0.7
+            is StringValue -> 2.0
+            is Result.Known<TYPE, RESULT, *> -> 1.2
+            is Result.Simple<TYPE, RESULT> -> 2.0
+            is Result.Empty -> ALMOST_ZERO
+        }
+    }
+
+    private fun <TYPE, RESULT> canMutate(node: Result<TYPE, RESULT>): Boolean {
+        return when (node) {
+            is Result.Simple<TYPE, RESULT> -> node.mutation === emptyMutation<RESULT>()
+            is Result.Known<TYPE, RESULT, *> -> node.value.mutations().isNotEmpty()
+            is Result.Recursive<TYPE, RESULT> -> node.modify.isNotEmpty()
+            is Result.Collection<TYPE, RESULT> -> node.modify.isNotEmpty() && node.iterations > 0
+            is Result.Empty<TYPE, RESULT> -> false
+        }
+    }
+
+    @Suppress("UNCHECKED_CAST")
+    private fun <TYPE, RESULT, T : KnownValue<T>> Result.Known<TYPE, RESULT, *>.mutate(mutation: Mutation<T>, random: Random, configuration: Configuration): Result.Known<TYPE, RESULT, T> {
+        val source: T = value as T
+        val mutate = mutation.mutate(source, random, configuration)
+        return Result.Known(
+            mutate,
+            build as (T) -> RESULT
+        )
+    }
+}
+
+private const val ALMOST_ZERO = 1E-7
+private val IDENTITY_MUTATION: (Any, random: Random) -> Any = { f, _ -> f }
+
+fun <RESULT> emptyMutation(): (RESULT, random: Random) -> RESULT {
+    @Suppress("UNCHECKED_CAST")
+    return IDENTITY_MUTATION as (RESULT, random: Random) -> RESULT
+}
+
 /**
  * Mutations is an object which applies some changes to the source object
  * and then returns a new object (or old one without changes).
@@ -14,20 +111,14 @@ fun interface Mutation<T> {
     fun mutate(source: T, random: Random, configuration: Configuration): T
 }
 
-inline fun <reified T, reified F : T> Mutation<F>.adapt(): Mutation<T> {
-    return Mutation { s, r, c ->
-        if (s is F) return@Mutation mutate(s, r, c) else s
-    }
-}
-
 sealed class BitVectorMutations : Mutation<BitVectorValue> {
 
     abstract fun rangeOfMutation(source: BitVectorValue): IntRange
 
     override fun mutate(source: BitVectorValue, random: Random, configuration: Configuration): BitVectorValue {
         with (rangeOfMutation(source)) {
             val firstBits = random.nextInt(start, endInclusive.coerceAtLeast(1))
-            return BitVectorValue(source).apply { this[firstBits] = !this[firstBits] }
+            return BitVectorValue(source, this@BitVectorMutations).apply { this[firstBits] = !this[firstBits] }
         }
     }
 
@@ -44,31 +135,194 @@ sealed class BitVectorMutations : Mutation<BitVectorValue> {
     }
 }
 
-sealed class IEEE754Mutations : Mutation<IEEE754Value> {
+sealed interface IEEE754Mutations : Mutation<IEEE754Value> {
 
-    object ChangeSign : IEEE754Mutations() {
+    object ChangeSign : IEEE754Mutations {
         override fun mutate(source: IEEE754Value, random: Random, configuration: Configuration): IEEE754Value {
-            return IEEE754Value(source).apply {
+            return IEEE754Value(source, this).apply {
                 setRaw(0, !getRaw(0))
             }
         }
     }
 
-    object Mantissa : IEEE754Mutations() {
+    object Mantissa : IEEE754Mutations {
         override fun mutate(source: IEEE754Value, random: Random, configuration: Configuration): IEEE754Value {
             val i = random.nextInt(0, source.mantissaSize)
-            return IEEE754Value(source).apply {
+            return IEEE754Value(source, this).apply {
                 setRaw(1 + exponentSize + i, !getRaw(1 + exponentSize + i))
             }
         }
     }
 
-    object Exponent : IEEE754Mutations() {
+    object Exponent : IEEE754Mutations {
         override fun mutate(source: IEEE754Value, random: Random, configuration: Configuration): IEEE754Value {
             val i = random.nextInt(0, source.exponentSize)
-            return IEEE754Value(source).apply {
+            return IEEE754Value(source, this).apply {
                 setRaw(1 + i, !getRaw(1 + i))
             }
         }
     }
+}
+
+sealed interface StringMutations : Mutation<StringValue> {
+
+    object AddCharacter : StringMutations {
+        override fun mutate(source: StringValue, random: Random, configuration: Configuration): StringValue {
+            val value = source.value
+            if (value.length >= configuration.maxStringLengthWhenMutated) {
+                return source
+            }
+            val position = random.nextInt(value.length + 1)
+            val charToMutate = if (value.isNotEmpty()) {
+                value.random(random)
+            } else {
+                // use any meaningful character from the ascii table
+                random.nextInt(33, 127).toChar()
+            }
+            val newString = buildString {
+                append(value.substring(0, position))
+                // try to change char to some that is close enough to origin char
+                val charTableSpread = 64
+                if (random.nextBoolean()) {
+                    append(charToMutate - random.nextInt(1, charTableSpread))
+                } else {
+                    append(charToMutate + random.nextInt(1, charTableSpread))
+                }
+                append(value.substring(position, value.length))
+            }
+            return StringValue(newString, lastMutation = this)
+        }
+    }
+
+    object RemoveCharacter : StringMutations {
+        override fun mutate(source: StringValue, random: Random, configuration: Configuration): StringValue {
+            val value = source.value
+            val position = random.nextInt(value.length + 1)
+            if (position >= value.length) return source
+            val toRemove = random.nextInt(value.length)
+            val newString = buildString {
+                append(value.substring(0, toRemove))
+                append(value.substring(toRemove + 1, value.length))
+            }
+            return StringValue(newString, this)
+        }
+    }
+}
+
+fun interface NodeMutation<TYPE, RESULT> : Mutation<Node<TYPE, RESULT>>
+
+sealed interface CollectionMutations<TYPE, RESULT> : Mutation<Pair<Result.Collection<TYPE, RESULT>, NodeMutation<TYPE, RESULT>>> {
+
+    override fun mutate(
+        source: Pair<Result.Collection<TYPE, RESULT>, NodeMutation<TYPE, RESULT>>,
+        random: Random,
+        configuration: Configuration
+    ): Pair<Result.Collection<TYPE, RESULT>, NodeMutation<TYPE, RESULT>> {
+        return mutate(source.first, source.second, random, configuration) to source.second
+    }
+
+    fun mutate(
+        source: Result.Collection<TYPE, RESULT>,
+        recursive: NodeMutation<TYPE, RESULT>,
+        random: Random,
+        configuration: Configuration
+    ) : Result.Collection<TYPE, RESULT>
+
+    class Shuffle<TYPE, RESULT> : CollectionMutations<TYPE, RESULT> {
+        override fun mutate(
+            source: Result.Collection<TYPE, RESULT>,
+            recursive: NodeMutation<TYPE, RESULT>,
+            random: Random,
+            configuration: Configuration
+        ): Result.Collection<TYPE, RESULT> {
+            return Result.Collection(
+                construct = source.construct,
+                modify = source.modify.toMutableList().shuffled(random),
+                iterations = source.iterations
+            )
+        }
+    }
+
+    class Mutate<TYPE, RESULT> : CollectionMutations<TYPE, RESULT> {
+        override fun mutate(
+            source: Result.Collection<TYPE, RESULT>,
+            recursive: NodeMutation<TYPE, RESULT>,
+            random: Random,
+            configuration: Configuration
+        ): Result.Collection<TYPE, RESULT> {
+            return Result.Collection(
+                construct = source.construct,
+                modify = source.modify.toMutableList().apply {
+                    val i = random.nextInt(0, source.modify.size)
+                    set(i, recursive.mutate(source.modify[i], random, configuration))
+                },
+                iterations = source.iterations
+            )
+        }
+    }
+}
+
+sealed interface RecursiveMutations<TYPE, RESULT> : Mutation<Pair<Result.Recursive<TYPE, RESULT>, NodeMutation<TYPE, RESULT>>> {
+
+    override fun mutate(
+        source: Pair<Result.Recursive<TYPE, RESULT>, NodeMutation<TYPE, RESULT>>,
+        random: Random,
+        configuration: Configuration
+    ): Pair<Result.Recursive<TYPE, RESULT>, NodeMutation<TYPE, RESULT>> {
+        return mutate(source.first, source.second, random, configuration) to source.second
+    }
+
+    fun mutate(
+        source: Result.Recursive<TYPE, RESULT>,
+        recursive: NodeMutation<TYPE, RESULT>,
+        random: Random,
+        configuration: Configuration
+    ) : Result.Recursive<TYPE, RESULT>
+
+
+    class Constructor<TYPE, RESULT> : RecursiveMutations<TYPE, RESULT> {
+        override fun mutate(
+            source: Result.Recursive<TYPE, RESULT>,
+            recursive: NodeMutation<TYPE, RESULT>,
+            random: Random,
+            configuration: Configuration
+        ): Result.Recursive<TYPE, RESULT> {
+            return Result.Recursive(
+                construct = recursive.mutate(source.construct,random, configuration),
+                modify = source.modify
+            )
+        }
+    }
+
+    class ShuffleAndCutModifications<TYPE, RESULT> : RecursiveMutations<TYPE, RESULT> {
+        override fun mutate(
+            source: Result.Recursive<TYPE, RESULT>,
+            recursive: NodeMutation<TYPE, RESULT>,
+            random: Random,
+            configuration: Configuration
+        ): Result.Recursive<TYPE, RESULT> {
+            return Result.Recursive(
+                construct = source.construct,
+                modify = source.modify.shuffled(random).take(random.nextInt(source.modify.size + 1).coerceAtLeast(1))
+            )
+        }
+    }
+
+    class Mutate<TYPE, RESULT> : RecursiveMutations<TYPE, RESULT> {
+        override fun mutate(
+            source: Result.Recursive<TYPE, RESULT>,
+            recursive: NodeMutation<TYPE, RESULT>,
+            random: Random,
+            configuration: Configuration
+        ): Result.Recursive<TYPE, RESULT> {
+            return Result.Recursive(
+                construct = source.construct,
+                modify = source.modify.toMutableList().apply {
+                    val i = random.nextInt(0, source.modify.size)
+                    set(i, recursive.mutate(source.modify[i], random, configuration))
+                }
+            )
+        }
+
+    }
 }