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// Copyright ©2018 The Gonum Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package optimize
import (
"math"
"gonum.org/v1/gonum/mat"
)
var _ Method = (*ListSearch)(nil)
// ListSearch finds the optimum location from a specified list of possible
// optimum locations.
type ListSearch struct {
// Locs is the list of locations to optimize. Each row of Locs is a location
// to optimize. The number of columns of Locs must match the dimensions
// passed to InitGlobal, and Locs must have at least one row.
Locs mat.Matrix
eval int
rows int
bestF float64
bestIdx int
}
func (*ListSearch) Uses(has Available) (uses Available, err error) {
return has.function()
}
// Init initializes the method for optimization. The input dimension
// must match the number of columns of Locs.
func (l *ListSearch) Init(dim, tasks int) int {
if dim <= 0 {
panic(nonpositiveDimension)
}
if tasks < 0 {
panic(negativeTasks)
}
r, c := l.Locs.Dims()
if r == 0 {
panic("listsearch: list matrix has no rows")
}
if c != dim {
panic("listsearch: supplied dimension does not match list columns")
}
l.eval = 0
l.rows = r
l.bestF = math.Inf(1)
l.bestIdx = -1
return min(r, tasks)
}
func (l *ListSearch) sendNewLoc(operation chan<- Task, task Task) {
task.Op = FuncEvaluation
task.ID = l.eval
mat.Row(task.X, l.eval, l.Locs)
l.eval++
operation <- task
}
func (l *ListSearch) updateMajor(operation chan<- Task, task Task) {
// Update the best value seen so far, and send a MajorIteration.
if task.F < l.bestF {
l.bestF = task.F
l.bestIdx = task.ID
} else {
task.F = l.bestF
mat.Row(task.X, l.bestIdx, l.Locs)
}
task.Op = MajorIteration
operation <- task
}
func (l *ListSearch) Status() (Status, error) {
if l.eval < l.rows {
return NotTerminated, nil
}
return MethodConverge, nil
}
func (l *ListSearch) Run(operation chan<- Task, result <-chan Task, tasks []Task) {
// Send initial tasks to evaluate
for _, task := range tasks {
l.sendNewLoc(operation, task)
}
// Read from the channel until PostIteration is sent or until the list of
// tasks is exhausted.
Loop:
for {
task := <-result
switch task.Op {
default:
panic("unknown operation")
case PostIteration:
break Loop
case MajorIteration:
if l.eval == l.rows {
task.Op = MethodDone
operation <- task
continue
}
l.sendNewLoc(operation, task)
case FuncEvaluation:
l.updateMajor(operation, task)
}
}
// Post iteration was sent, or the list has been completed. Read in the final
// list of tasks.
for task := range result {
switch task.Op {
default:
panic("unknown operation")
case MajorIteration:
case FuncEvaluation:
l.updateMajor(operation, task)
}
}
close(operation)
}
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