# Differential Equation Parameter Estimation Using Only A Subset of Variables

You have to use the documented form: http://docs.juliadiffeq.org/latest/basics/common_solver_opts.html#Miscellaneous-1

1 Like

Ok
Thanks for pointing me to the right place A

Hi Chris,
I have this working - but I have noticed one last issue that I amnot sure how to incorporate to my loose function.
I am using L2 which i think is pretty standard to find the parameters that minimize the differences between my data and my DAE solution.
However, while the scale of u1 is in untis or u16 in e-3, u19 is on the scale of e5 - I assume this makes the parameters to preferentially fit the data of e19 to minimize L2 - neglecting the fit of u1 or u16
Do you know of a way to incorporate a scaling factor that scale by the maximum of each u in L2 or a loss function that might be a better fit for this clearly different scales?

Thanks

ale

you can add weights to the L2, or define some more in depth cost function which weights terms by the maximum of u.

So something like this?

``````w=fill(0.0,21)
for i in 1:21
w[i]=maximum(mock_data[i,:])
end
w=sqrt.(1 ./ w)

loss_objective(mp_, dat) = build_loss_objective(model_ode(mp_), Rodas5(), L2Loss(t,dat;data_weight=w),maxiters=100000)
juobj(args...) = loss_objective(args, mock_data)(args)
``````

Thanks,

A

Yes

One, I think last question.
My variables are not necessarily measured at the same time -
i may have u1 measured at 3,6 and 9 days and u4 at 5,10,and 15 days for example.
Is there a way to incorporate the heterogeneous times of measurement into the L2loss function?

Thanks,

A

No, at that point you should probably use the interface to write a custom loss function.

Thanks -
would this make sense to you?

``````L2(t, dat) = sum(L2Loss(t[i],dat[i]) for i in length(t))
``````

A

``````L2(sol) = sum(abs2,dat[i] - sol(t[i]))`
``````

for example. So now any function on the solution, write the one you need.

So I ended adapting your L2Loss function to do what I wanted -
here is the code, as it belongs to you as much or more than it does to me!
Thanks for the help ``````struct L2Loss2{T,D,W} <: DiffEqBase.DECostFunction
t::T
data::D
data_weight::W
end

function (f::L2Loss2)(sol::DiffEqBase.DESolution)
data = f.data
weight = f.data_weight

if sol.retcode != :Success
return Inf
end

sumsq = 0.0

if weight == nothing
println(length(sol), length(data))
@inbounds for i in 1:length(data)
#         println(data[i], " ", length(data[i]))
#         println(sol(t[i])[i,:], " ", length(sol(t[i])[i,:]))
for j in 2:length(data[i])
#                 println(data[i][j]," ",sol(t[i])[i,:][j] )
#                 println(data[i][j] == sol(t[i])[i,:][j])
sumsq +=(data[i][j] - sol(t[i])[i,:][j])^2
end
end
else
@inbounds for i in 1:length(data)
if typeof(weight) <: Real
for j in 2:length(data[i])
sumsq = sumsq + ((data[i][j] - sol(t[i])[i,:][j])^2)*weight
end
else
for j in 2:length(data[i])
sumsq = sumsq + ((data[i][j] - sol(t[i])[i,:][j])^2)*weight[i,j]
end
end
end
end
sumsq
end

# Cost functions are written assuming a data matrix
# Turn vectors into a 1xN matrix
matrixize(x) = typeof(x) <: Vector ? reshape(x,1,length(x)) : x

L2Loss2(t,data;data_weight=nothing) = L2Loss2(t,matrixize(data),
matrixize(data_weight))
``````

First time i get to use struct Thanks,

A

1 Like

Hi Chris -

I been trying to parallelize the process above - and it works pretty well when I script it, but it does not when i write it as a function - it seems that I can not distribute function arguments to run internal functions in parallel - this is the simples example I can think off (I’ve been trying to use your ParallelDataTransfer.jl) package:

What I would like to do is make function arguments available to all processes within a function -
ie

function(a)
@everywhere a=\$a
@everywhere println(a)
end

but this does not work - below I have two examples- I appreciate any light you may shed, I’ve been looking at this for a couple of days now, and I am pretty baffled.

``````@everywhere function test(ag)
sendto(workers(),ag=ag)
@everywhere println(ag)
end
test(5)
``````

This is the trace:

5
On worker 2:
UndefVarError: ag not defined
top-level scope at none:0
eval at ./boot.jl:319
#116 at /opt/julia-1.0.0/share/julia/stdlib/v1.0/Distributed/src/process_messages.jl:276
run_work_thunk at /opt/julia-1.0.0/share/julia/stdlib/v1.0/Distributed/src/process_messages.jl:56
run_work_thunk at /opt/julia-1.0.0/share/julia/stdlib/v1.0/Distributed/src/process_messages.jl:65
#remotecall_wait#154(::Base.Iterators.Pairs{Union{},Union{},Tuple{},NamedTuple{(),Tuple{}}}, ::Function, ::Function, ::Distributed.Worker, ::Module, ::Vararg{Any,N} where N) at /opt/julia-1.0.0/share/julia/stdlib/v1.0/Distributed/src/remotecall.jl:407
remotecall_wait(::Function, ::Distributed.Worker, ::Module, ::Vararg{Any,N} where N) at /opt/julia-1.0.0/share/julia/stdlib/v1.0/Distributed/src/remotecall.jl:398
#remotecall_wait#157(::Base.Iterators.Pairs{Union{},Union{},Tuple{},NamedTuple{(),Tuple{}}}, ::Function, ::Function, ::Int64, ::Module, ::Vararg{Any,N} where N) at /opt/julia-1.0.0/share/julia/stdlib/v1.0/Distributed/src/remotecall.jl:419
remotecall_wait(::Function, ::Int64, ::Module, ::Vararg{Any,N} where N) at /opt/julia-1.0.0/share/julia/stdlib/v1.0/Distributed/src/remotecall.jl:419

…and 16 more exception(s).

Stacktrace:
 remotecall_eval(::Module, ::Array{Int64,1}, ::Expr) at /opt/julia-1.0.0/share/julia/stdlib/v1.0/Distributed/src/macros.jl:207
 macro expansion at /opt/julia-1.0.0/share/julia/stdlib/v1.0/Distributed/src/macros.jl:190 [inlined]
 test(::Int64) at ./In:4
 top-level scope at In:7

when I modify function:

``````@everywhere function test2(ag3)
println(ag3)
@everywhere local ag4=ag3
println(ag4)
@everywhere println(ag4)
end
test2(5)
``````

same issues:

n worker 2:
UndefVarError: ag3 not defined
top-level scope at none:0
eval at ./boot.jl:319
#116 at /opt/julia-1.0.0/share/julia/stdlib/v1.0/Distributed/src/process_messages.jl:276
run_work_thunk at /opt/julia-1.0.0/share/julia/stdlib/v1.0/Distributed/src/process_messages.jl:56
run_work_thunk at /opt/julia-1.0.0/share/julia/stdlib/v1.0/Distributed/src/process_messages.jl:65
#remotecall_wait#154(::Base.Iterators.Pairs{Union{},Union{},Tuple{},NamedTuple{(),Tuple{}}}, ::Function, ::Function, ::Distributed.Worker, ::Module, ::Vararg{Any,N} where N) at /opt/julia-1.0.0/share/julia/stdlib/v1.0/Distributed/src/remotecall.jl:407
remotecall_wait(::Function, ::Distributed.Worker, ::Module, ::Vararg{Any,N} where N) at /opt/julia-1.0.0/share/julia/stdlib/v1.0/Distributed/src/remotecall.jl:398
#remotecall_wait#157(::Base.Iterators.Pairs{Union{},Union{},Tuple{},NamedTuple{(),Tuple{}}}, ::Function, ::Function, ::Int64, ::Module, ::Vararg{Any,N} where N) at /opt/julia-1.0.0/share/julia/stdlib/v1.0/Distributed/src/remotecall.jl:419
remotecall_wait(::Function, ::Int64, ::Module, ::Vararg{Any,N} where N) at /opt/julia-1.0.0/share/julia/stdlib/v1.0/Distributed/src/remotecall.jl:419

…and 16 more exception(s).

Stacktrace:
 remotecall_eval(::Module, ::Array{Int64,1}, ::Expr) at /opt/julia-1.0.0/share/julia/stdlib/v1.0/Distributed/src/macros.jl:207
 macro expansion at /opt/julia-1.0.0/share/julia/stdlib/v1.0/Distributed/src/macros.jl:190 [inlined]
 test2(::Int64) at ./In:3
 top-level scope at In:8

Do you have any idea on how to fix this issue- I want to make my function arguments available to every process, but I can’t seem to make the processes see them -

Thaks

I feel like I’m wading into a private conversation here, but anyway: Your code snippets don’t account to an MWE, so it’s hard to say what’s going wrong. This works:

``````julia> using Distributed

2-element Array{Int64,1}:
2
3

julia> function printeverywhere(a)
@everywhere a = \$a
@everywhere println(a)
end
printeverywhere (generic function with 1 method)

julia> printeverywhere(5)
5
From worker 2:    5
From worker 3:    5
``````
1 Like

Thanks so much -
no private at all. It’s just Chris has been extremely helpful with DAE and fitting advice-

A

by the way what does MWE stand for? English is not my first language- so I still have issues with acronyms-

Thanks again

Apologies I was actually going to link that acronym to this post which explains it in a bit more detail: Minimum Working Example, which means basically a code snippet that contains as little code as possible, and allows others to copy/paste it to run on their local machine and replicate your issue.

This helps in three ways:

1. Often your problem disappears when you attempt to construct the MWE, as you strip away unnecessary parts of your code and mode clearly isolate the issue yourself;
2. If others fail to replicate your issue, it can then point to problems with your installation/Julia version/hardware etc.; and
3. Others can play around with different possible solutions much more easily if they can actually run your code.
1 Like

I see -

My issue is that I couldn’t move past this stage, so just getting the variable to be seen by all processes as in your code was the solution (I hope) to y issues!

``````@everywhere function fit_to_data(model,IC,tspan, t, data, lower, upper, varnum, algnum=0;kwargs...)

@everywhere model = \$model
@everywhere IC = \$IC
@everywhere tspan = \$tspan
@everywhere t = \$t
@everywhere data = \$data
@everywhere println(data)
@every0hwere lower=\$lower
@everywhere upper=\$upper
@everywhere varnum=\$varnum
@everywhere algnum=\$algnum

end
``````

UndefVarError: data not defined

Stacktrace:
 top-level scope at /opt/julia-1.0.0/share/julia/stdlib/v1.0/Distributed/src/macros.jl:189
 top-level scope at In:1

once I remove @everywhere from in front the function name - following your example my variables are seen and I can use my function - so you did solve my issue… Not sure why this works like this, but I have not doe much parallel programming before, so I am not always certain how to make information available to the correct processes.

Thanks again.

A

so continuing with the conversation before -
I still can’t figure out how to solve my issue, I can parallelize processes in script form, but not in function form -

For example:

``````@everywhere function g(du,u,p,t)
σ,ρ,β = p
x,y,z = u
du = dx = σ*(y-x)
du = dy = x*(ρ-z) - y
du = dz = x*y - β*z
end

@everywhere l2=Float64.([0, 0, 0])
@everywhere u2=Float64.([20, 30, 10])

@everywhere u0 = [1.0;0.0;0.0]
@everywhere t = 0.0:0.05:1.0
@everywhere tspan = (0.0,1.0)
@everywhere model_ode(p_) = ODEProblem(g, u0, tspan,p_)
@everywhere solve_model(mp_,s, i) = DifferentialEquations.solve(model_ode(mp_), Tsit5(),saveat=s, save_idxs=i)
@everywhere mock_data = Array(solve_model([10.0,28.0,8/3],0.05,[1,2,3]))

@everywhere function L(t,dat,w=nothing)
return L2Loss(t,dat;data_weight=w)
end

@everywhere loss_objective(mp_, dat)=build_loss_objective(model_ode(mp_), Tsit5(), L(t,dat))
@everywhere bbobj(args) = loss_objective(args, mock_data)(args)

opts = bbsetup(bbobj; Method=:separable_nes, SearchRange = collect(zip(l2,u2)),
NumDimensions = 3, MaxFuncEvals = 50000, workers=workers())

bb3=bboptimize(opts);

``````

will run the optimization in parallel -

my issue happend when I wan to wrap this script in a function - and use modl, data, etc as parameters
As you see every variable is defined everywhere in the script

if I do

``````#using mock_data from above

@everywhere function f(model,data)
@everywhere l2=Float64.([0, 0, 0])
@everywhere u2=Float64.([20, 30, 10])

@everywhere u0 = [1.0;0.0;0.0]
@everywhere t = 0.0:0.05:1.0
@everywhere tspan = (0.0,1.0)
@everywhere model_ode(p_) = ODEProblem(model, u0, tspan,p_)

Tsit5(),saveat=s, save_idxs=i)

@everywhere L(t,dat,w=nothing)  =L2Loss(t,dat;data_weight=w)

@everywhere loss_objective(mp_, dat)=build_loss_objective(model_ode(mp_), Tsit5(), L(t,dat))
@everywhere bbobj(args) = loss_objective(args, data)(args)

opts = bbsetup(bbobj; Method=:separable_nes, SearchRange = collect(zip(l2,u2)),
NumDimensions = 3, MaxFuncEvals = 50000, workers=workers())

bb3=bboptimize(opts);
end

f(g,mock_data)
``````

I get errors where model and data are not recognized and if I skip the @everyhwere in front of f it runs in only one process -

My goal is to have the optimization to run in parallel, for any model, dataset I want to pass, but not sure how to do that-

Thanks,

A

I think there is misunderstanding about parallelizing by multiprocessing. First of all, if everything is in a function one `@everywhere` at the beginning is enough. One way to parallelize computation is by computing gradient values of your model(`g`) in different processes by spawning. Another is that you may want to process more than one model&data pair by spawning `f` with different arguments in each process. Either way, `@everywhere` is not magic doing it for you. Here, it only defines methods or variables. I suggest reading related references from documentation.

1 Like

Thanks,
I’ll double check-
It’s been working well for other functions that’s were the confusion arose from. (I check with top how many processes are running)-and for simpler functions I get good distribution of the processes. I’ll check how to improve it.
Thanks again.
A