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rootfind with p #125

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merged 3 commits into from
Oct 16, 2023
Merged

rootfind with p #125

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c3d0e5c
rootfind with p
lindnemi May 15, 2023
c20296a
add suggestions
lindnemi Oct 16, 2023
cbaf49f
fix keyword error
lindnemi Oct 16, 2023
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23 changes: 12 additions & 11 deletions src/Utilities.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -169,14 +169,15 @@ function find_fixpoint(nd, p, initial_guess)
return nl_res.zero
else
println("Failed to find fixpoint. Algorithm did not converge.")
println("Try running nlsolve with other options.")
end
end

export RootRhs

"""
struct RootRhs
RootRhs(of)
RootRhs(nd)

A utility function that provides a root function, to find valid initial
conditions. The operator ``M^\\dagger M - 1`` projects onto the kernel of ``M``.
Expand All @@ -191,32 +192,32 @@ struct RootRhs
rhs
mpm
end
function (rr::RootRhs)(x)
function (rr::RootRhs)(x,p)
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hm commit suggestion is gone...

maybe just

function (rr:RootRhs)(x, p=nothing, t=nothing)

to achieve the old behavior? Also might be worth adding an option for t. Maybe nothing would be the better default than 0.0 since it screams a the user in case there is an explicit t dependency.

Bit off topic, but since the rhs and mpm fields are not typed the inner loop of nlsolve will be type unstable. But this might not be a problem in practice as it converges fast for small systems and for large systems the matrix multiply cost might dominate the runtime dispatch cost 🤷‍♂️

f_x = similar(x)
rr.rhs(f_x, x, nothing, 0.0)
rr.mpm * f_x .- f_x
rr.rhs(f_x, x, p, 0.0)
return rr.mpm * f_x .- f_x
end

function RootRhs(of)
mm = of.mass_matrix
function RootRhs(nd)
mm = nd.mass_matrix
@assert mm !== nothing
mpm = pinv(mm) * mm
RootRhs(of.f, mpm)
return RootRhs(nd.f, mpm)
end


export find_valid_ic


"""
find_valid_ic(of, ic_guess)
find_valid_ic(nd, ic_guess)

Try to find valid initial conditions for problems involving mass matrices.
Uses RootRhs as residual function.
"""
function find_valid_ic(of, ic_guess)
rr = RootRhs(of)
nl_res = nlsolve(rr, ic_guess)
function find_valid_ic(nd, initial_guess; p=nothing)
rr = RootRhs(nd)
nl_res = nlsolve(x -> rr(x,p), initial_guess)
if converged(nl_res) == true
return nl_res.zero
else
Expand Down