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ChrisRackauckasChrisRackauckas
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Merge pull request #56 from huiyuxie/main
Fix Issue #34: Add new method Alefeld, Potra, Shi (1995)
2 parents df85c3f + e44bab2 commit 8eb8afc

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4 files changed

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lines changed

‎Project.toml‎

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -43,4 +43,4 @@ StaticArrays = "90137ffa-7385-5640-81b9-e52037218182"
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Test = "8dfed614-e22c-5e08-85e1-65c5234f0b40"
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[targets]
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test = ["BenchmarkTools", "SafeTestsets", "Pkg", "Test", "StaticArrays", "NNlib"]
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test = ["BenchmarkTools", "SafeTestsets", "Pkg", "Test", "StaticArrays", "NNlib"]

‎src/SimpleNonlinearSolve.jl‎

Lines changed: 3 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -38,6 +38,7 @@ include("brent.jl")
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include("dfsane.jl")
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include("ad.jl")
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include("halley.jl")
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include("alefeld.jl")
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import SnoopPrecompile
4344

@@ -59,13 +60,13 @@ SnoopPrecompile.@precompile_all_calls begin for T in (Float32, Float64)
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=#
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prob_brack = IntervalNonlinearProblem{false}((u, p) -> u * u - p, T.((0.0, 2.0)), T(2))
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for alg in (Bisection, Falsi, Ridder, Brent)
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for alg in (Bisection, Falsi, Ridder, Brent, Alefeld)
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solve(prob_brack, alg(), abstol = T(1e-2))
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end
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end end
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# DiffEq styled algorithms
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export Bisection, Brent, Broyden, LBroyden, SimpleDFSane, Falsi, Halley, Klement,
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Ridder, SimpleNewtonRaphson, SimpleTrustRegion
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Ridder, SimpleNewtonRaphson, SimpleTrustRegion, Alefeld
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end # module

‎src/alefeld.jl‎

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Original file line numberDiff line numberDiff line change
@@ -0,0 +1,184 @@
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"""
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`Alefeld()`
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An implementation of algorithm 4.2 from [Alefeld](https://dl.acm.org/doi/10.1145/210089.210111).
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The paper brought up two new algorithms. Here choose to implement algorithm 4.2 rather than
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algorithm 4.1 because, in certain sense, the second algorithm(4.2) is an optimal procedure.
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"""
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struct Alefeld <: AbstractBracketingAlgorithm end
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function SciMLBase.solve(prob::IntervalNonlinearProblem,
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alg::Alefeld, args...; abstol = nothing,
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reltol = nothing,
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maxiters = 1000, kwargs...)
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f = Base.Fix2(prob.f, prob.p)
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a, b = prob.tspan
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c = a - (b - a) / (f(b) - f(a)) * f(a)
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fc = f(c)
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if iszero(fc)
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return SciMLBase.build_solution(prob, alg, c, fc;
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retcode = ReturnCode.Success,
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left = a,
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right = b)
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end
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a, b, d = _bracket(f, a, b, c)
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e = zero(a) # Set e as 0 before iteration to avoid a non-value f(e)
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# Begin of algorithm iteration
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for i in 2:maxiters
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# The first bracketing block
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f₁, f₂, f₃, f₄ = f(a), f(b), f(d), f(e)
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if i == 2 || (f₁ == f₂ || f₁ == f₃ || f₁ == f₄ || f₂ == f₃ || f₂ == f₄ || f₃ == f₄)
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c = _newton_quadratic(f, a, b, d, 2)
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else
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c = _ipzero(f, a, b, d, e)
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if (c - a) * (c - b) ≥ 0
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c = _newton_quadratic(f, a, b, d, 2)
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end
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end
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ē, fc = d, f(c)
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(a == c || b == c) &&
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return SciMLBase.build_solution(prob, alg, c, fc;
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retcode = ReturnCode.FloatingPointLimit,
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left = a,
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right = b)
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iszero(fc) &&
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return SciMLBase.build_solution(prob, alg, c, fc;
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retcode = ReturnCode.Success,
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left = a,
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right = b)
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ā, b̄, d̄ = _bracket(f, a, b, c)
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# The second bracketing block
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f₁, f₂, f₃, f₄ = f(ā), f(b̄), f(d̄), f(ē)
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if f₁ == f₂ || f₁ == f₃ || f₁ == f₄ || f₂ == f₃ || f₂ == f₄ || f₃ == f₄
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c = _newton_quadratic(f, ā, b̄, d̄, 3)
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else
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c = _ipzero(f, ā, b̄, d̄, ē)
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if (c - ā) * (c - b̄) ≥ 0
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c = _newton_quadratic(f, ā, b̄, d̄, 3)
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end
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end
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fc = f(c)
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(ā == c || b̄ == c) &&
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return SciMLBase.build_solution(prob, alg, c, fc;
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retcode = ReturnCode.FloatingPointLimit,
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left = ā,
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right = b̄)
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iszero(fc) &&
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return SciMLBase.build_solution(prob, alg, c, fc;
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retcode = ReturnCode.Success,
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left = ā,
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right = b̄)
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ā, b̄, d̄ = _bracket(f, ā, b̄, c)
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# The third bracketing block
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if abs(f(ā)) < abs(f(b̄))
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u = ā
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else
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u = b̄
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end
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c = u - 2 * (b̄ - ā) / (f(b̄) - f(ā)) * f(u)
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if (abs(c - u)) > 0.5 * (b̄ - ā)
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c = 0.5 * (ā + b̄)
87+
end
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fc = f(c)
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(ā == c || b̄ == c) &&
90+
return SciMLBase.build_solution(prob, alg, c, fc;
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retcode = ReturnCode.FloatingPointLimit,
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left = ā,
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right = b̄)
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iszero(fc) &&
95+
return SciMLBase.build_solution(prob, alg, c, fc;
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retcode = ReturnCode.Success,
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left = ā,
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right = b̄)
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ā, b̄, d = _bracket(f, ā, b̄, c)
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# The last bracketing block
102+
if b̄ - ā < 0.5 * (b - a)
103+
a, b, e = ā, b̄, d̄
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else
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e = d
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c = 0.5 * (ā + b̄)
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fc = f(c)
108+
(ā == c || b̄ == c) &&
109+
return SciMLBase.build_solution(prob, alg, c, fc;
110+
retcode = ReturnCode.FloatingPointLimit,
111+
left = ā,
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right = b̄)
113+
iszero(fc) &&
114+
return SciMLBase.build_solution(prob, alg, c, fc;
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retcode = ReturnCode.Success,
116+
left = ā,
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right = b̄)
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a, b, d = _bracket(f, ā, b̄, c)
119+
end
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end
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# Reassign the value a, b, and c
123+
if b == c
124+
b = d
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elseif a == c
126+
a = d
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end
128+
fc = f(c)
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130+
# Reuturn solution when run out of max interation
131+
return SciMLBase.build_solution(prob, alg, c, fc; retcode = ReturnCode.MaxIters,
132+
left = a, right = b)
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end
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# Define subrotine function bracket, check fc before bracket to return solution
136+
function _bracket(f::F, a, b, c) where F
137+
if iszero(f(c))
138+
ā, b̄, d = a, b, c
139+
else
140+
if f(a) * f(c) < 0
141+
ā, b̄, d = a, c, b
142+
elseif f(b) * f(c) < 0
143+
ā, b̄, d = c, b, a
144+
end
145+
end
146+
147+
return ā, b̄, d
148+
end
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150+
# Define subrotine function newton quadratic, return the approximation of zero
151+
function _newton_quadratic(f::F, a, b, d, k) where F
152+
A = ((f(d) - f(b)) / (d - b) - (f(b) - f(a)) / (b - a)) / (d - a)
153+
B = (f(b) - f(a)) / (b - a)
154+
155+
if iszero(A)
156+
return a - (1 / B) * f(a)
157+
elseif A * f(a) > 0
158+
rᵢ₋₁ = a
159+
else
160+
rᵢ₋₁ = b
161+
end
162+
163+
for i in 1:k
164+
rᵢ = rᵢ₋₁ - (f(a) + B * (rᵢ₋₁ - a) + A * (rᵢ₋₁ - a) * (rᵢ₋₁ - b)) / (B + A * (2 * rᵢ₋₁ - a - b))
165+
rᵢ₋₁ = rᵢ
166+
end
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168+
return rᵢ₋₁
169+
end
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171+
# Define subrotine function ipzero, also return the approximation of zero
172+
function _ipzero(f::F, a, b, c, d) where F
173+
Q₁₁ = (c - d) * f(c) / (f(d) - f(c))
174+
Q₂₁ = (b - c) * f(b) / (f(c) - f(b))
175+
Q₃₁ = (a - b) * f(a) / (f(b) - f(a))
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D₂₁ = (b - c) * f(c) / (f(c) - f(b))
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D₃₁ = (a - b) * f(b) / (f(b) - f(a))
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Q₂₂ = (D₂₁ - Q₁₁) * f(b) / (f(d) - f(b))
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Q₃₂ = (D₃₁ - Q₂₁) * f(a) / (f(c) - f(a))
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D₃₂ = (D₃₁ - Q₂₁) * f(c) / (f(c) - f(a))
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Q₃₃ = (D₃₂ - Q₂₂) * f(a) / (f(d) - f(a))
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183+
return a + Q₃₁ + Q₃₂ + Q₃₃
184+
end

‎test/basictests.jl‎

Lines changed: 12 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -210,6 +210,18 @@ for p in 1.1:0.1:100.0
210210
@test ForwardDiff.derivative(g, p) ≈ 1 / (2 * sqrt(p))
211211
end
212212

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# Alefeld
214+
g = function (p)
215+
probN = IntervalNonlinearProblem{false}(f, typeof(p).(tspan), p)
216+
sol = solve(probN, Alefeld())
217+
return sol.u
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end
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for p in 1.1:0.1:100.0
221+
@test g(p) ≈ sqrt(p)
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@test ForwardDiff.derivative(g, p) ≈ 1 / (2 * sqrt(p))
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end
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213225
f, tspan = (u, p) -> p[1] * u * u - p[2], (1.0, 100.0)
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t = (p) -> [sqrt(p[2] / p[1])]
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p = [0.9, 50.0]

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