Exemplo n.º 1
0
func (mini *Minimizer) Step() {
	m := M.Buffer()
	size := m.Size()
	k := mini.k
	h := mini.h

	// save original magnetization
	m0 := cuda.Buffer(3, size)
	defer cuda.Recycle(m0)
	data.Copy(m0, m)

	// make descent
	cuda.Minimize(m, m0, k, h)

	// calculate new torque for next step
	k0 := cuda.Buffer(3, size)
	defer cuda.Recycle(k0)
	data.Copy(k0, k)
	torqueFn(k)
	setMaxTorque(k) // report to user

	// just to make the following readable
	dm := m0
	dk := k0

	// calculate step difference of m and k
	cuda.Madd2(dm, m, m0, 1., -1.)
	cuda.Madd2(dk, k, k0, -1., 1.) // reversed due to LLNoPrecess sign

	// get maxdiff and add to list
	max_dm := cuda.MaxVecNorm(dm)
	mini.lastDm.Add(max_dm)
	setLastErr(mini.lastDm.Max()) // report maxDm to user as LastErr

	// adjust next time step
	var nom, div float32
	if NSteps%2 == 0 {
		nom = cuda.Dot(dm, dm)
		div = cuda.Dot(dm, dk)
	} else {
		nom = cuda.Dot(dm, dk)
		div = cuda.Dot(dk, dk)
	}
	if div != 0. {
		mini.h = nom / div
	} else { // in case of division by zero
		mini.h = 1e-4
	}

	M.normalize()

	// as a convention, time does not advance during relax
	NSteps++
}
Exemplo n.º 2
0
Arquivo: energy.go Projeto: jsampaio/3
// vector dot product
func dot(a, b outputField) float64 {
	A, recyA := a.Slice()
	if recyA {
		defer cuda.Recycle(A)
	}
	B, recyB := b.Slice()
	if recyB {
		defer cuda.Recycle(B)
	}
	return float64(cuda.Dot(A, B))
}
Exemplo n.º 3
0
// average of slice over the magnet volume
func sAverageMagnet(s *data.Slice) []float64 {
	if geometry.Gpu().IsNil() {
		return sAverageUniverse(s)
	} else {
		avg := make([]float64, s.NComp())
		for i := range avg {
			avg[i] = float64(cuda.Dot(s.Comp(i), geometry.Gpu())) / magnetNCell()
			checkNaN1(avg[i])
		}
		return avg
	}
}
Exemplo n.º 4
0
func Relax() {
	SanityCheck()
	pause = false

	// Save the settings we are changing...
	prevType := solvertype
	prevErr := MaxErr
	prevFixDt := FixDt
	prevPrecess := Precess

	// ...to restore them later
	defer func() {
		SetSolver(prevType)
		MaxErr = prevErr
		FixDt = prevFixDt
		Precess = prevPrecess
		relaxing = false
		//	Temp.upd_reg = prevTemp
		//	Temp.invalidate()
		//	Temp.update()
	}()

	// Set good solver for relax
	SetSolver(BOGAKISHAMPINE)
	FixDt = 0
	Precess = false
	relaxing = true

	// Minimize energy: take steps as long as energy goes down.
	// This stops when energy reaches the numerical noise floor.
	const N = 3 // evaluate energy (expensive) every N steps
	relaxSteps(N)
	E0 := GetTotalEnergy()
	relaxSteps(N)
	E1 := GetTotalEnergy()
	for E1 < E0 && !pause {
		relaxSteps(N)
		E0, E1 = E1, GetTotalEnergy()
	}

	// Now we are already close to equilibrium, but energy is too noisy to be used any further.
	// So now we minimize the total torque which is less noisy and does not have to cross any
	// bumps once we are close to equilibrium.
	solver := stepper.(*RK23)
	defer stepper.Free() // purge previous rk.k1 because FSAL will be dead wrong.
	avgTorque := func() float32 {
		return cuda.Dot(solver.k1, solver.k1)
	}
	var T0, T1 float32 = 0, avgTorque()

	// Step as long as torque goes down. Then increase the accuracy and step more.
	for MaxErr > 1e-9 && !pause {
		MaxErr /= math.Sqrt2
		relaxSteps(N) // TODO: Play with other values
		T0, T1 = T1, avgTorque()
		for T1 < T0 && !pause {
			relaxSteps(N) // TODO: Play with other values
			T0, T1 = T1, avgTorque()
		}
	}

	pause = true
}