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/*
Copyright (C) 2019 Leo Tenenbaum
This file is part of AutoArt.
AutoArt is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
AutoArt is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with AutoArt. If not, see <https://www.gnu.org/licenses/>.
*/
package autoutils
import (
"math"
"math/rand"
"fmt"
)
// Operators
const (
CONST = iota
ADD
SUB
MUL
DIV
MIN
MAX
SQRT
SIN
COS
TAN
LOG
EXP
OPERATOR_COUNT
)
const FIRST_BINARY = ADD
const FIRST_UNARY = SQRT
const BINARY_COUNT = FIRST_UNARY - 1 // -1 for CONST
const UNARY_COUNT = OPERATOR_COUNT - FIRST_UNARY
const FIRST_VAR = OPERATOR_COUNT
type Operator struct {
op int // Operator number. If operator is a variable, v, it is equal to FIRST_VAR + v
constant float64 // Constant (if op = CONST)
}
type Function struct {
nvars int
operators []Operator
}
// Generate a random function f with the given length (i.e. len(f.operators))
// and the given number of variables
func (f *Function) Generate(nvars int, length int) {
f.nvars = nvars
f.operators = make([]Operator, length)
nsOnStack := 0
i := 0
for nsOnStack + i < length {
var operator Operator
var optype int
if nsOnStack == 0 {
// Pick a random variable
optype = 0
} else if nsOnStack == 1 {
// Pick a constant/variable/unary operator
optype = rand.Intn(3)
} else {
// Pick a constant/variable/unary/binary operator
optype = rand.Intn(4)
}
switch optype {
case 0:
// variable
operator.op = FIRST_VAR + rand.Intn(nvars)
nsOnStack++
case 1:
// Constant
operator.op = CONST
operator.constant = rand.Float64()
nsOnStack++
case 2:
// unary
operator.op = rand.Intn(UNARY_COUNT) + FIRST_UNARY
case 3:
// binary
operator.op = rand.Intn(BINARY_COUNT) + FIRST_BINARY
nsOnStack--
}
f.operators[i] = operator
i++
}
if nsOnStack + i == length {
// Add a unary operator
f.operators[i].op = rand.Intn(UNARY_COUNT) + FIRST_UNARY
i++
}
// Keep adding binary operators until nsOnStack == 1
for nsOnStack > 1 {
f.operators[i].op = rand.Intn(BINARY_COUNT) + FIRST_BINARY
nsOnStack--
i++
}
}
func (f *Function) Evaluate(vars []float64) float64 {
var stack []float64
for _, op := range f.operators {
l := len(stack)
switch (op.op) {
case CONST:
stack = append(stack, op.constant)
case ADD:
stack[l-2] += stack[l-1]
stack = stack[:l-1]
case SUB:
stack[l-2] -= stack[l-1]
stack = stack[:l-1]
case MUL:
stack[l-2] *= stack[l-1]
stack = stack[:l-1]
case DIV:
if stack[l-1] == 0 { // Check for division by 0
stack[l-1] = 0.01
}
stack[l-2] /= stack[l-1]
stack = stack[:l-1]
case MIN:
stack[l-2] = math.Min(stack[l-2], stack[l-1])
stack = stack[:l-1]
case MAX:
stack[l-2] = math.Max(stack[l-2], stack[l-1])
stack = stack[:l-1]
case SQRT:
stack[l-1] = math.Sqrt(math.Abs(stack[l-1]))
case SIN:
stack[l-1] = math.Sin(stack[l-1])
case COS:
stack[l-1] = math.Cos(stack[l-1])
case TAN:
stack[l-1] = math.Tan(stack[l-1])
case LOG:
stack[l-1] = math.Log(math.Abs(stack[l-1]))
case EXP:
stack[l-1] = math.Exp(stack[l-1])
default:
stack = append(stack, vars[op.op - FIRST_VAR])
}
}
return stack[0]
}
func (f *Function) String() string {
var str string
for _, op := range f.operators {
switch (op.op) {
case CONST:
str += fmt.Sprintf("%v",op.constant)
case ADD:
str += "+"
case SUB:
str += "-"
case MUL:
str += "*"
case DIV:
str += "/"
case SQRT:
str += "sqrt"
case SIN:
str += "sin"
case COS:
str += "cos"
case TAN:
str += "tan"
default:
str += fmt.Sprintf("v%v", op.op - FIRST_VAR)
}
str += " "
}
return str
}
const mutationRate = 0.01
func (f *Function) Mutate() {
for i, op := range f.operators {
if op.op == CONST && rand.Float64() < mutationRate {
f.operators[i].constant += rand.NormFloat64() / 5 // Nudge constant
}
}
}
func (f *Function) Breed(f1* Function, f2 *Function) {
// f(x) = (f1(x) + f2(x)) / 2
f.operators = make([]Operator, len(f1.operators) + len(f2.operators) + 3)
for i, o := range f1.operators {
f.operators[i] = o
}
for i, o := range f2.operators {
f.operators[i + len(f1.operators)] = o
}
i := len(f1.operators) + len(f2.operators)
f.operators[i].op = ADD
f.operators[i+1].op = CONST
f.operators[i+1].constant = 2
f.operators[i+2].op = DIV
}
func (f *Function) CopyFrom(other *Function) {
f.nvars = other.nvars
f.operators = make([]Operator, len(other.operators))
for i, op := range other.operators {
f.operators[i] = op
}
}
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