func main() {
cuda.Init()
N0, N1, N2 := 1, 64, 128
c := 1.
mesh := data.NewMesh(N0, N1, N2, c/2, c*2, c)
m := cuda.NewSlice(3, mesh)
conv := cuda.NewDemag(mesh)
cuda.Memset(m, 1, 1, 1)
B := cuda.NewSlice(3, mesh)
Bsat := 1.
vol := data.NilSlice(1, mesh)
conv.Exec(B, m, vol, Bsat)
out := B.HostCopy()
bx := out.Vectors()[0][N0/2][N1/2][N2/2]
by := out.Vectors()[1][N0/2][N1/2][N2/2]
bz := out.Vectors()[2][N0/2][N1/2][N2/2]
fmt.Println("demag tensor:", bx, by, bz)
check(bx, -1)
check(by, 0)
check(bz, 0)
fmt.Println("OK")
}
func main() {
cuda.Init()
N0, N1, N2 := 16, 16, 16
c := 1.
mesh := data.NewMesh(N0, N1, N2, c, c, c)
m := cuda.NewSlice(3, mesh)
conv := cuda.NewDemag(mesh)
mhost := m.HostCopy()
m_ := mhost.Vectors()
r := float64(N2) / 2
for i := 0; i < N0; i++ {
x := c * (float64(i) + 0.5 - float64(N0)/2)
for j := 0; j < N1; j++ {
y := c * (float64(j) + 0.5 - float64(N1)/2)
for k := 0; k < N2; k++ {
z := c * (float64(k) + 0.5 - float64(N2)/2)
if x*x+y*y+z*z < r*r {
m_[0][i][j][k] = 1
m_[1][i][j][k] = 2
m_[2][i][j][k] = 3
}
}
}
}
data.Copy(m, mhost)
B := cuda.NewSlice(3, mesh)
conv.Exec(B, m, data.NilSlice(1, mesh), 1)
out := B.HostCopy()
bx := out.Vectors()[0][N0/2][N1/2][N2/2]
by := out.Vectors()[1][N0/2][N1/2][N2/2]
bz := out.Vectors()[2][N0/2][N1/2][N2/2]
fmt.Println("demag tensor:", bx, by/2, bz/3)
check(bx, -1./3.)
check(by, -2./3.)
check(bz, -3./3.)
fmt.Println("OK")
}
func initialize() {
// these 2 GPU arrays are re-used to stored various quantities.
arr1, arr2 := cuda.NewSynced(3, mesh), cuda.NewSynced(3, mesh)
// cell volumes currently unused
vol = data.NilSlice(1, mesh)
// magnetization
m = newBuffered(arr1, "m", nil)
M = m
// effective field
b_eff := newBuffered(arr2, "B_eff", nil)
B_eff = b_eff
// demag field
demag_ := cuda.NewDemag(mesh)
b_demag := newBuffered(arr2, "B_demag", func(b *data.Slice) {
m_ := m.Read()
demag_.Exec(b, m_, vol, Mu0*Msat()) //TODO: consistent msat or bsat
m.ReadDone()
})
B_demag = b_demag
// exchange field
b_exch := newAdder("B_exch", func(dst *data.Slice) {
m_ := m.Read()
cuda.AddExchange(dst, m_, Aex(), Msat())
m.ReadDone()
})
B_exch = b_exch
// Dzyaloshinskii-Moriya field
b_dmi := newAdder("B_dmi", func(dst *data.Slice) {
d := DMI()
if d != 0 {
m_ := m.Read()
cuda.AddDMI(dst, m_, d, Msat())
m.ReadDone()
}
})
B_dmi = b_dmi
// uniaxial anisotropy
b_uni := newAdder("B_uni", func(dst *data.Slice) {
ku1 := Ku1() // in J/m3
if ku1 != [3]float64{0, 0, 0} {
m_ := m.Read()
cuda.AddUniaxialAnisotropy(dst, m_, ku1[2], ku1[1], ku1[0], Msat())
m.ReadDone()
}
})
B_uni = b_uni
// external field
b_ext := newAdder("B_ext", func(dst *data.Slice) {
bext := B_ext()
cuda.AddConst(dst, float32(bext[2]), float32(bext[1]), float32(bext[0]))
})
// llg torque
torque := newBuffered(arr2, "torque", func(b *data.Slice) {
m_ := m.Read()
cuda.LLGTorque(b, m_, b, float32(Alpha()))
m.ReadDone()
})
Torque = torque
// spin-transfer torque
stt := newAdder("stt", func(dst *data.Slice) {
j := J()
if j != [3]float64{0, 0, 0} {
m_ := m.Read()
p := SpinPol()
jx := j[2] * p
jy := j[1] * p
jz := j[0] * p
cuda.AddZhangLiTorque(dst, m_, [3]float64{jx, jy, jz}, Msat(), nil, Alpha(), Xi())
m.ReadDone()
}
})
STT = stt
// data table
table := newTable("datatable")
Table = table
// solver
torqueFn := func(good bool) *data.Synced {
m.touch(good) // saves if needed
table.send(m.Synced, good)
b_demag.update(good)
b_exch.addTo(b_eff, good)
b_dmi.addTo(b_eff, good)
b_uni.addTo(b_eff, good)
b_ext.addTo(b_eff, good)
b_eff.touch(good)
torque.update(good)
stt.addTo(torque, good)
return torque.Synced
}
Solver = cuda.NewHeun(m.Synced, torqueFn, cuda.Normalize, 1e-15, Gamma0, &Time)
}