Not able to update initial conditions and stop time of Lorenz example

[HildingElmqvist]

I wanted to allow for changing stop time and initial conditions in the Lorenz example. However, when adding the following code to the update function, I get trouble when updating integ:
`

prob = ODEProblem{true, SciMLBase.FullSpecialize}(lorenz!, u0, (0.0, stop), p) 

integ = init(prob, Tsit5(), dense = true)`

The error message in the browser is:
`

lorenz.wasm:0xd7 Uncaught RuntimeError: unreachable

at lorenz.wasm:0xd7

at run ((index):76:16)

at async (index):78:15`

Is there some other way of changing initial conditions and stop time which does not imply updating the global variable integ

[tshort]

I think the best way to handle changes to stop times and initial conditions is to use the integrator interface. Run step!(integ) inside a loop in the update() function. That's how I started statically compiling these DiffEq models. It should give more control.

On a side note, the next versions of Firefox and Chrome will support these apps without any experimental flags. The demos now work with the beta versions of Chrome and Firefox without flags. These releases are coming next month. I've updated the code to only use the features coming out next month.

[HildingElmqvist]

I now read the documentation of OrdinaryDiffEq more carefully and realized that I could do:
OrdinaryDiffEq.reinit!(integ, initial, tf=stopTime)
So the problem is solved.

Great that the experimental features will be available in the next release of Chrome.

[HildingElmqvist]

There is one problem with:
OrdinaryDiffEq.reinit!(integ, initial, tf=stopTime)
I can't change the size of the u vector from what is given in:
prob = ODEProblem{true, SciMLBase.FullSpecialize}(lorenz!,u0,tspan,p)
I have tried
`
OrdinaryDiffEq.resize!(integ, n)

OrdinaryDiffEq.set_u!(integ, init)`

giving unreachable code or
[wasm-validator error in function julia_errorTuple_String__String_] struct.new operand 0 must have proper type, on (struct.new $struct.0 (local.get $5) )

For the moment, I am using an oversized u vector which can handle all the different models I want to switch between. I hope a better solution would be given in the future.

I assume there would be a similar problem if one would like to change the solver method.

[tshort]

Resizing sounds like a problem that's tough to work around given that we bake in the integrator as a global variable. In theory, we can enlarge arrays, but I'm not sure how well it works with global variables. Your oversized vector sounds like the way to go.

[geordie2020]

Hi, thank you for your great effort, first of all!
I'm a beginner with both Julia and WASM.

Is it expected behaviour, that i can't set

global integ = init(prob, Tsit5(), dense = true)

from a WASM exported function?
When trying, i get:

ERROR: LoadError: type Argument has no field value

Also, when i try to define it in the global scope

integ = init(prob, Tsit5(), dense = true)

it gives

ERROR: LoadError: KeyError: key 12 not found

The only way to make it compile, seems to be

const integ = init(prob, Tsit5(), dense = true)

Context: besides trying to include the creation of the integrator in another WASM exported function setupIntegrator(), i'm using an exported update(), like you do in https://github.com/tshort/WebAssemblyCompiler.jl/blob/main/examples/lorenz/lorenz.jl

[tshort]

@geordie2020, I'm not following that. Can you post a bigger part of the code?

[geordie2020]

Sure, my end goal is something like:

function n_body(du, u, p, t)
    ...
end

global integ 

function setupNBodyIntegrator()
	n = 4 # number of bodies. should later be an arg to this fn.
	dim = 2
	order = 2

	param = ones(Float64, n) * 1
	# println("param $param")

	u_begin_pos = rand(Float64, round(Int64, n * dim * order / 2))
	u_begin_vel = ones(Float64, round(Int64, n * dim * order / 2))
	u_begin = vcat(u_begin_pos, u_begin_vel)
	# println("u_begin $u_begin")

	t_begin = 0.0
	t_end = 10.0
	tspan = (t_begin, t_end)
	# println("tspan $tspan")

	prob = OrdinaryDiffEq.ODEProblem{true, SciMLBase.FullSpecialize}(n_body, u_begin, tspan, param)
	global integ = init(prob, Tsit5(), dense = false, dtmax = 0.03)
    nothing
end

function updateStep()
	step!(integ)
	u = integ.sol.u[end][1:div(end, 2)]
	return JS.object(u)
end

using Base.Experimental: @overlay
@overlay WebAssemblyCompiler.MT @inline SciMLBase.check_error(integrator::SciMLBase.DEIntegrator) = SciMLBase.ReturnCode.Success
# The following function includes a try/catch, so bypass it.
@overlay WebAssemblyCompiler.MT @inline OrdinaryDiffEq.ode_determine_initdt(args...; kw...) = 0.001

WebAssemblyCompiler.debug(:inline)

WebAssemblyCompiler.compile((updateStep,), (setupNBodyIntegrator,), filepath = "wasmtest1.wasm", validate = true, optimize = false, experimental = false)

I'm not sure, what i changed, but currently the error is:

ERROR: LoadError: UndefVarError: `integ` not defined
Stacktrace:
  [1] top-level scope
    @ :0

This is compiling and working fine:

function n_body(du, u, p, t)
    ...
end

# println("### START setupNBodyIntegrator")
n = 4 # number of bodies.
dim = 2
order = 2

param = ones(Float64, n) * 1
# println("param $param")

u_begin_pos = rand(Float64, round(Int64, n * dim * order / 2))
u_begin_vel = ones(Float64, round(Int64, n * dim * order / 2))
u_begin = vcat(u_begin_pos, u_begin_vel)
# println("u_begin $u_begin")

t_begin = 0.0
t_end = 10.0
tspan = (t_begin, t_end)
# println("tspan $tspan")

prob = OrdinaryDiffEq.ODEProblem{true, SciMLBase.FullSpecialize}(n_body, u_begin, tspan, param)
const integ = init(prob, Tsit5(), dense = false, dtmax = 0.03)
# println("### END setupNBodyIntegrator")

function updateStep()
	step!(integ)
	u = integ.sol.u[end][1:div(end, 2)]
	return JS.object(u)
end

using Base.Experimental: @overlay
@overlay WebAssemblyCompiler.MT @inline SciMLBase.check_error(integrator::SciMLBase.DEIntegrator) = SciMLBase.ReturnCode.Success
# The following function includes a try/catch, so bypass it.
@overlay WebAssemblyCompiler.MT @inline OrdinaryDiffEq.ode_determine_initdt(args...; kw...) = 0.001

WebAssemblyCompiler.debug(:inline)

WebAssemblyCompiler.compile((updateStep,); filepath = "wasmtest1.wasm", validate = true, optimize = false, experimental = false)

[dominic-chang]

Hi I'm trying to build the docs for this example from source, but am unable to because of the following error:
KeyError: key 50 not found

I get this error executing the compilation on this line:

https://github.com/tshort/WebAssemblyCompiler.jl/blob/e2fa9a9183721703c345d830aea3a7655e4fda52/examples/lorenz/lorenz.jl#L117C64-L117C69