func TestQuadratic(t *testing.T) {
mat.Register(cops)
n := 10
xStar := mat.NewVec(n)
xStar.AddSc(1)
A := mat.RandN(n)
At := A.TrView()
AtA := mat.New(n)
AtA.Mul(At, A)
bTmp := mat.NewVec(n)
bTmp.Apply(A, xStar)
b := mat.NewVec(n)
b.Apply(At, bTmp)
b.Scal(-2)
c := bTmp.Nrm2Sq()
//Define input arguments
obj := opt.NewQuadratic(AtA, b, c)
p := NewParams()
sol := NewSolution(mat.NewVec(n))
//Steepest descent with armijo
stDesc := NewSteepestDescent()
res1 := stDesc.Solve(obj, sol, p, NewDisplay(100))
t.Log(res1.ObjX, res1.FunEvals, res1.GradEvals, res1.Status)
//Steepest descent with Quadratic
stDesc.LineSearch = uni.DerivWrapper{uni.NewQuadratic()}
res2 := stDesc.Solve(obj, sol, p, NewDisplay(100))
t.Log(res2.ObjX, res2.FunEvals, res2.GradEvals, res2.Status)
//LBFGS with armijo
lbfgs := NewLBFGS()
res3 := lbfgs.Solve(obj, sol, p, NewDisplay(10))
t.Log(res3.ObjX, res3.FunEvals, res3.GradEvals, res3.Status)
//constrained problems (constraints described as projection)
projGrad := NewProjGrad()
res4 := projGrad.Solve(obj, opt.RealPlus{}, sol, p, NewDisplay(100))
t.Log(res4.ObjX, res4.FunEvals, res4.GradEvals, res4.Status)
if math.Abs(res1.ObjX) > 0.01 {
t.Fail()
}
if math.Abs(res2.ObjX) > 0.01 {
t.Fail()
}
if math.Abs(res3.ObjX) > 0.01 {
t.Fail()
}
if math.Abs(res4.ObjX) > 0.01 {
t.Fail()
}
}
//Predictor-Corrector Interior Point implementation
func (sol *PredCorr) Solve(prob *Problem, p *Params, u ...Updater) *Result {
res := NewResult(prob)
h := newHelper(u)
A := prob.A
m, n := A.Dims()
At := A.TrView()
var mu, sigma float64
res.X.AddSc(1)
res.S.AddSc(1)
res.Rd = mat.NewVec(n)
res.Rp = mat.NewVec(m)
res.Rs = mat.NewVec(n)
x := res.X
s := res.S
y := res.Y
dx := mat.NewVec(n)
ds := mat.NewVec(n)
dy := mat.NewVec(m)
dxAff := mat.NewVec(n)
dsAff := mat.NewVec(n)
dyAff := mat.NewVec(m)
dxCC := mat.NewVec(n)
dsCC := mat.NewVec(n)
dyCC := mat.NewVec(m)
xdivs := mat.NewVec(n)
temp := mat.New(m, n)
lhs := mat.New(m, m)
rhs := mat.NewVec(m)
soli := mat.NewVec(m)
triU := mat.New(m, m)
triUt := triU.TrView()
nTemp1 := mat.NewVec(n)
nTemp2 := mat.NewVec(n)
alpha := 0.0
for {
res.Rd.Sub(prob.C, res.S)
res.Rd.AddMul(At, res.Y, -1)
res.Rp.Apply(A, res.X)
res.Rp.Sub(prob.B, res.Rp)
res.Rs.Mul(res.X, res.S)
res.Rs.Neg(res.Rs)
if h.update(res, p); res.Status != 0 {
break
}
if checkKKT(res, p); res.Status != 0 {
break
}
mu = res.Rs.Asum() / float64(n)
//determining left hand side
temp.ScalCols(A, xdivs.Div(x, s))
lhs.Mul(temp, At)
//factorization
lhs.Chol(triU)
//right hand side
nTemp1.Add(res.Rd, s)
nTemp1.Mul(nTemp1, xdivs)
rhs.Apply(A, nTemp1)
rhs.Add(rhs, res.Rp)
//solving for dyAff
soli.Trsv(triUt, rhs)
dyAff.Trsv(triU, soli)
//calculating other steps (dxAff, dsAff)
nTemp1.Apply(At, dyAff)
dxAff.Sub(nTemp1, res.Rd)
dxAff.Sub(dxAff, s)
dxAff.Mul(dxAff, xdivs)
dsAff.Div(dxAff, xdivs)
dsAff.Add(dsAff, s)
dsAff.Neg(dsAff)
//determining step size
alpha = 1.0
for i := range dxAff {
if dxAff[i] < 0 {
alph := -x[i] / dxAff[i]
if alph < alpha {
alpha = alph
}
}
}
for i := range dsAff {
if dsAff[i] < 0 {
alph := -s[i] / dsAff[i]
if alph < alpha {
alpha = alph
}
}
}
alpha *= 0.99995
//calculating duality gap measure for affine case
nTemp1.Copy(x)
nTemp1.Axpy(alpha, dxAff)
nTemp2.Copy(s)
nTemp2.Axpy(alpha, dsAff)
mu_aff := mat.Dot(nTemp1, nTemp2) / float64(n)
//centering parameter
sigma = math.Pow(mu_aff/mu, 3)
//right hand side for predictor corrector step
res.Rs.Mul(dxAff, dsAff)
res.Rs.Neg(res.Rs)
res.Rs.AddSc(sigma * mu_aff)
nTemp1.Div(res.Rs, s)
nTemp1.Neg(nTemp1)
rhs.Apply(A, nTemp1)
//solving for dyCC
soli.Trsv(triUt, rhs)
dyCC.Trsv(triU, soli)
//calculating other steps (dxAff, dsAff)
nTemp1.Apply(At, dyCC)
dxCC.Mul(nTemp1, x)
dxCC.Add(res.Rs, dxCC)
dxCC.Div(dxCC, s)
dsCC.Mul(dxCC, s)
dsCC.Sub(res.Rs, dsCC)
dsCC.Div(dsCC, x)
dx.Add(dxAff, dxCC)
dy.Add(dyAff, dyCC)
ds.Add(dsAff, dsCC)
alpha = 1
for i := range dx {
if dx[i] < 0 {
alph := -x[i] / dx[i]
if alph < alpha {
alpha = alph
}
}
}
for i := range ds {
if ds[i] < 0 {
alph := -s[i] / ds[i]
if alph < alpha {
alpha = alph
}
}
}
alpha *= 0.99995
x.Axpy(alpha, dx)
y.Axpy(alpha, dy)
s.Axpy(alpha, ds)
}
return res
}
