func direcbetween(from, to *optim.Point, m optim.Mesh) []int {
d := make([]int, from.Len())
step := m.Step()
for i, x0 := range from.Pos {
d[i] = int((to.Pos[i] - x0) / step)
}
return d
}
func pointFromDirec(from *optim.Point, direc []int, m optim.Mesh) *optim.Point {
pos := make([]float64, from.Len())
step := m.Step()
for i, x0 := range from.Pos {
pos[i] = x0 + float64(direc[i])*step
}
return &optim.Point{m.Nearest(pos), math.Inf(1)}
}
// Poll polls on mesh m centered on point from. It is responsible for
// selecting points and evaluating them with ev using obj. If a better
// point was found, it returns success == true, the point, and number of
// evaluations. If a better point was not found, it returns false, the
// from point, and the number of evaluations. If err is non-nil, success
// must be false and best must be from - neval may be non-zero.
func (cp *Poller) Poll(obj optim.Objectiver, ev optim.Evaler, m optim.Mesh, from *optim.Point) (success bool, best *optim.Point, neval int, err error) {
best = from
if cp.Spanner == nil {
cp.Spanner = Compass2N{}
}
pollpoints := []*optim.Point{}
// Only poll compass directions if we haven't polled from this point
// before. DONT DELETE - this can fire sometimes if the mesh isn't
// allowed to contract below a certain step (i.e. integer meshes).
h := from.Hash()
if h != cp.prevhash || cp.prevstep != m.Step() {
// TODO: write test that checks we poll compass dirs again if only mesh
// step changed (and not from point)
pollpoints = genPollPoints(from, cp.Spanner, m)
cp.prevhash = h
} else {
// Use random directions instead.
n := len(genPollPoints(from, cp.Spanner, m))
pollpoints = genPollPoints(from, &RandomN{N: n}, m)
}
cp.prevstep = m.Step()
// Add successful directions from last poll. We want to add these points
// in front of the other points so we can potentially stop earlier if
// polling opportunistically.
perms := optim.Rand.Perm(len(pollpoints))
// this is an extra safety check to make sure we don't index out of bounds
// on the perms slice
max := len(cp.keepdirecs)
if max > len(perms) {
max = len(perms)
}
for i, dir := range cp.keepdirecs[:max] {
swapindex := perms[i]
pollpoints[swapindex] = pointFromDirec(from, dir.dir, m)
}
// project points onto feasible region and mesh grid
if m != nil {
for _, p := range pollpoints {
p.Pos = m.Nearest(p.Pos)
}
}
cp.points = make([]*optim.Point, 0, len(pollpoints))
if cp.SkipEps == 0 {
cp.points = pollpoints
} else {
for _, p := range pollpoints {
// It is possible that due to the mesh gridding, the poll point is
// outside of constraints or bounds and will be rounded back to the
// current point. Check for this and skip the poll point if this is
// the case.
dist := optim.L2Dist(from, p)
if dist > cp.SkipEps {
cp.points = append(cp.points, p)
}
}
}
objstop := &objStopper{Objectiver: obj, Best: from.Val}
results, n, err := ev.Eval(objstop, cp.points...)
if err != nil && err != FoundBetterErr {
return false, best, n, err
}
// this is separate from best to allow all points better than from to be
// added to keepdirecs before we update the best point.
nextbest := from
// Sort results and keep the best Nkeep as poll directions.
for _, p := range results {
if p.Val < best.Val {
cp.keepdirecs = append(cp.keepdirecs, direc{direcbetween(from, p, m), p.Val})
}
if p.Val < nextbest.Val {
nextbest = p
}
}
best = nextbest
nkeep := cp.Nkeep
if max := len(pollpoints) / 4; max < nkeep {
nkeep = max
}
sort.Sort(byval(cp.keepdirecs))
if len(cp.keepdirecs) > nkeep {
cp.keepdirecs = cp.keepdirecs[:nkeep]
}
if best.Val < from.Val {
return true, best, n, nil
} else {
return false, from, n, nil
}
}
// Iterate mutates m and so for each iteration, the same, mutated m should be
// passed in.
func (m *Method) Iterate(o optim.Objectiver, mesh optim.Mesh) (best *optim.Point, n int, err error) {
if m.count == 0 {
m.origstep = mesh.Step()
} else if mesh.Step() < m.ResetStep {
mesh.SetStep(m.origstep)
}
var nevalsearch, nevalpoll int
var success bool
defer m.updateDb(&nevalsearch, &nevalpoll, mesh.Step())
m.count++
prevstep := mesh.Step()
if !m.DiscreteSearch {
mesh.SetStep(0)
}
success, best, nevalsearch, err = m.Searcher.Search(o, mesh, m.Curr)
mesh.SetStep(prevstep)
n += nevalsearch
if err != nil {
return best, n, err
} else if success {
m.Curr = best
return best, n, nil
}
// It is important to recenter mesh on new best point before polling.
// This is necessary because the search may not be operating on the
// current mesh grid. This doesn't need to happen if search succeeds
// because search either always operates on the same grid, or always
// operates in continuous space.
mesh.SetOrigin(m.Curr.Pos) // TODO: test that this doesn't get set to Zero pos [0 0 0...] on first iteration.
success, best, nevalpoll, err = m.Poller.Poll(o, m.ev, mesh, m.Curr)
m.Poller.Spanner.Update(mesh.Step(), success)
n += nevalpoll
if err != nil {
return m.Curr, n, err
} else if success {
m.Curr = best
m.nsuccess++
if m.nsuccess == m.NsuccessGrow { // == allows -1 to mean never grow
mesh.SetStep(mesh.Step() * 2.0)
m.nsuccess = 0 // reset after resize
}
// Important to recenter mesh on new best point. More particularly,
// the mesh may have been resized and the new best may not lie on the
// previous mesh grid.
mesh.SetOrigin(best.Pos)
return best, n, nil
} else {
m.nsuccess = 0
var err error
mesh.SetStep(mesh.Step() * 0.5)
if mesh.Step() == 0 {
err = ZeroStepErr
}
return m.Curr, n, err
}
}
