Switch to add/remove instruction mutation

grow/definition.go

@@ -4,7 +4,6 @@ import "io"
 
 import "gopkg.in/yaml.v2"
 
-import "github.com/firestuff/subcoding/gen"
 import "github.com/firestuff/subcoding/vm"
 
 type Definition struct {
@@ -37,10 +36,19 @@ func (def *Definition) Grow(statusChan chan<- Status) (*vm.Program, error) {
 		statusChan <- status
 	}
 
+	prog := &vm.Program{
+		GlobalMemorySize:   def.GlobalMemorySize,
+		FunctionMemorySize: def.FunctionMemorySize,
+		InstructionLimit:   def.InstructionLimit,
+		Functions: []*vm.Function{
+			&vm.Function{},
+		},
+	}
+
 	for {
 		status.Attempts++
 
-		prog := gen.RandProgram(def.GlobalMemorySize, def.FunctionMemorySize, def.InstructionLimit)
+		Mutate(prog)
 
 		score, err := def.score(prog)
 		if err != nil {

grow/defs/mul_five.yaml

@@ -1,6 +1,6 @@
 global_memory_size: 1
 function_memory_size: 1
-instruction_limit: 2
+instruction_limit: 10
 samples:
 - in:  [0]
   out: [0]

grow/mutate.go

@@ -0,0 +1,36 @@
+package grow
+
+import "math"
+import "math/rand"
+
+import "github.com/firestuff/subcoding/gen"
+import "github.com/firestuff/subcoding/vm"
+
+func Mutate(prog *vm.Program) {
+	target := int(math.Max(2, rand.NormFloat64()*10+15))
+
+	if len(prog.Functions[0].Instructions) < target {
+		addInstruction(prog, prog.Functions[0])
+	} else {
+		removeInstruction(prog, prog.Functions[0])
+	}
+}
+
+func addInstruction(prog *vm.Program, fnc *vm.Function) {
+	if len(fnc.Instructions) == 0 {
+		fnc.Instructions = append(fnc.Instructions, gen.RandInstruction(prog))
+	} else {
+		i := rand.Intn(len(fnc.Instructions))
+		fnc.Instructions = append(fnc.Instructions[:i+1], fnc.Instructions[i:]...)
+		fnc.Instructions[i] = gen.RandInstruction(prog)
+	}
+}
+
+func removeInstruction(prog *vm.Program, fnc *vm.Function) {
+	if len(fnc.Instructions) == 0 {
+		return
+	}
+
+	i := rand.Intn(len(fnc.Instructions))
+	fnc.Instructions = append(fnc.Instructions[:i], fnc.Instructions[i+1:]...)
+}