86 lines
2.3 KiB
Go
86 lines
2.3 KiB
Go
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// CookieJar - A contestant's algorithm toolbox
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// Copyright (c) 2014 Peter Szilagyi. All rights reserved.
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//
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// CookieJar is dual licensed: use of this source code is governed by a BSD
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// license that can be found in the LICENSE file. Alternatively, the CookieJar
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// toolbox may be used in accordance with the terms and conditions contained
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// in a signed written agreement between you and the author(s).
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package utility
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import (
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"math"
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"gopkg.in/karalabe/cookiejar.v2/collections/bag"
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)
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// Data-source based utility, normalizing and transforming an input stream by an
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// assigned curve.
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type inputUtility struct {
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curve Curve // Data transformation curve
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min, max float64 // Normalization limits
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nonZero bool // Flag whether absolute zero output is allowed
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children *bag.Bag // Derived utilities based on the current one
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reset bool // Flag whether the output is not yet calculated
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input float64 // Input value which to o map to the curve
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output float64 // Cached output utility value
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}
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// Creates a new data source utility and associated a transformation curve.
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func newInputUtility(curve Curve, nonZero bool) *inputUtility {
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return &inputUtility{
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curve: curve,
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nonZero: nonZero,
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children: bag.New(),
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reset: true,
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}
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}
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// Sets the data limits used during normalization.
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func (u *inputUtility) Limit(min, max float64) {
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u.min, u.max = min, max
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u.Reset()
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}
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// Updates the utility to a new data value.
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func (u *inputUtility) Update(input float64) {
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u.input = input
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u.Reset()
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}
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// Resets the utility, requiring a reevaluation.
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func (u *inputUtility) Reset() {
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if !u.reset {
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u.reset = true
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u.children.Do(func(util interface{}) {
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util.(*comboUtility).Reset()
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})
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}
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}
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// Adds a new dependency to the utility hierarchy.
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func (u *inputUtility) Dependency(util utility) {
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u.children.Insert(util)
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}
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// Returns the utility value for the set data point.
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func (u *inputUtility) Evaluate() float64 {
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// Recalculate the output value if not cached
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if u.reset {
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// Normalize the input and calculate the output
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if diff := u.max - u.min; diff != 0 {
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u.input = (u.input - u.min) / diff
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}
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u.output = math.Min(1, math.Max(0, u.curve(u.input)))
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// If requested, prevent a result of absolute zero
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if u.nonZero && u.output == 0 {
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u.output = float64(1e-18)
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}
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u.reset = false
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}
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return u.output
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}
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