# Resizing ODE integrator with matrix or VectorOfArray initial condition

**URL:** <https://discourse.julialang.org/t/resizing-ode-integrator-with-matrix-or-vectorofarray-initial-condition/89583>\
**Category:** General Usage\
**Tags:** differentialequation, elasticarrays\
**Created:** [October 31, 2022, 9:23pm UTC](https://discourse.julialang.org/t/resizing-ode-integrator-with-matrix-or-vectorofarray-initial-condition/89583 "2022-10-31T21:23:57Z")\
**Posts on this page:** 4\
**Page:** 1

<div class="post-metadata">

**Author:** ![DanielVandH](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/danielvandh/32/31134_2.png) [@DanielVandH](https://discourse.julialang.org/u/DanielVandH)\
**Post date:** [October 31, 2022, 9:23pm UTC](https://discourse.julialang.org/t/resizing-ode-integrator-with-matrix-or-vectorofarray-initial-condition/89583/1 "2022-10-31T21:23:57Z")

</div>

Consider the following:

```julia
using OrdinaryDiffEq
using ElasticArrays
function sysde!(du, u, p, t)
    du[:, 1] .= rand(2)
    du[:, 2] .= rand(2)
    du[:, 3] .= rand(2)
    nothing 
end
u0 = ElasticArray{Float64}([0.0 0.0 0.0; 0.0 0.0 0.0])
tspan=(0.0,1.0)
prob=ODEProblem(sysde!, u0, tspan)
integrator = init(prob,Tsit5())
resize!(integrator, 4) # fails

```

```julia
ERROR: MethodError: no method matching resize!(::ElasticMatrix{Float64, Vector{Float64}}, ::Int64)
Closest candidates are:
  resize!(::OrdinaryDiffEq.ODEIntegrator, ::Int64) at C:\Users\licer\.julia\packages\OrdinaryDiffEq\c2Dwp\src\integrators\integrator_interface.jl:117
  resize!(::SciMLBase.DEIntegrator, ::Int64) at C:\Users\licer\.julia\packages\SciMLBase\cJ8FF\src\integrator_interface.jl:20
  resize!(::OrdinaryDiffEq.AbstractNLSolver, ::Any, ::Int64) at C:\Users\licer\.julia\packages\OrdinaryDiffEq\c2Dwp\src\nlsolve\utils.jl:407
  ...
Stacktrace:
 [1] resize!(integrator::OrdinaryDiffEq.ODEIntegrator{Tsit5, true, ElasticMatrix{Float64, Vector{Float64}}, Nothing, Float64, SciMLBase.NullParameters, Float64, Float64, Float64, Float64, Vector{ElasticMatrix{Float64, Vector{Float64}}}, ODESolution{Float64, 3, Vector{ElasticMatrix{Float64, Vector{Float64}}}, Nothing, Nothing, Vector{Float64}, Vector{Vector{ElasticMatrix{Float64, Vector{Float64}}}}, ODEProblem{ElasticMatrix{Float64, Vector{Float64}}, Tuple{Float64, Float64}, true, SciMLBase.NullParameters, ODEFunction{true, SciMLBase.AutoSpecialize, typeof(sysde!), UniformScaling{Bool}, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, typeof(SciMLBase.DEFAULT_OBSERVED), Nothing, Nothing}, Base.Pairs{Symbol, Union{}, Tuple{}, NamedTuple{(), Tuple{}}}, SciMLBase.StandardODEProblem}, Tsit5, OrdinaryDiffEq.InterpolationData{ODEFunction{true, SciMLBase.AutoSpecialize, typeof(sysde!), UniformScaling{Bool}, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, typeof(SciMLBase.DEFAULT_OBSERVED), Nothing, Nothing}, Vector{ElasticMatrix{Float64, Vector{Float64}}}, Vector{Float64}, Vector{Vector{ElasticMatrix{Float64, Vector{Float64}}}}, OrdinaryDiffEq.Tsit5Cache{ElasticMatrix{Float64, Vector{Float64}}, ElasticMatrix{Float64, Vector{Float64}}, ElasticMatrix{Float64, Vector{Float64}}, OrdinaryDiffEq.Tsit5ConstantCache{Float64, Float64}}}, DiffEqBase.DEStats}, ODEFunction{true, SciMLBase.AutoSpecialize, typeof(sysde!), UniformScaling{Bool}, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, typeof(SciMLBase.DEFAULT_OBSERVED), Nothing, Nothing}, OrdinaryDiffEq.Tsit5Cache{ElasticMatrix{Float64, Vector{Float64}}, ElasticMatrix{Float64, Vector{Float64}}, ElasticMatrix{Float64, Vector{Float64}}, OrdinaryDiffEq.Tsit5ConstantCache{Float64, Float64}}, OrdinaryDiffEq.DEOptions{Float64, Float64, Float64, Float64, PIController{Rational{Int64}}, typeof(DiffEqBase.ODE_DEFAULT_NORM), typeof(opnorm), Nothing, CallbackSet{Tuple{}, Tuple{}}, typeof(DiffEqBase.ODE_DEFAULT_ISOUTOFDOMAIN), typeof(DiffEqBase.ODE_DEFAULT_PROG_MESSAGE), typeof(DiffEqBase.ODE_DEFAULT_UNSTABLE_CHECK), DataStructures.BinaryHeap{Float64, DataStructures.FasterForward}, DataStructures.BinaryHeap{Float64, DataStructures.FasterForward}, Nothing, Nothing, Int64, Tuple{}, Tuple{}, Tuple{}}, ElasticMatrix{Float64, Vector{Float64}}, Float64, Nothing, OrdinaryDiffEq.DefaultInit}, i::Int64)
   @ OrdinaryDiffEq C:\Users\licer\.julia\packages\OrdinaryDiffEq\c2Dwp\src\integrators\integrator_interface.jl:123
 [2] top-level scope
   @ 

```

I want to be able to resize the integrator so that `u0` has an extra column. Is there any way to do that with `resize!`, or how can I define a new method to do it?

I initially wanted to use a vector of vectors, but that has the same issue:

```julia
using OrdinaryDiffEq
using RecursiveArrayTools
function sysde!(du, u, p, t)
    du[1] .= rand(2)
    du[2] .= rand(2)
    du[3] .= rand(2)
    nothing
end
u0 = VectorOfArray([[0.0,0.0],[0.0,0.0],[0.0,0.0]])
tspan = (0.0, 1.0)
prob = ODEProblem(sysde!, u0, tspan)
integrator = init(prob, Tsit5())
resize!(integrator, 4) # fails

```

```julia
ERROR: MethodError: no method matching resize!(::VectorOfArray{Float64, 2, Vector{Vector{Float64}}}, ::Int64)
Closest candidates are:
  resize!(::OrdinaryDiffEq.ODEIntegrator, ::Int64) at C:\Users\licer\.julia\packages\OrdinaryDiffEq\c2Dwp\src\integrators\integrator_interface.jl:117
  resize!(::SciMLBase.DEIntegrator, ::Int64) at C:\Users\licer\.julia\packages\SciMLBase\cJ8FF\src\integrator_interface.jl:20
  resize!(::OrdinaryDiffEq.AbstractNLSolver, ::Any, ::Int64) at C:\Users\licer\.julia\packages\OrdinaryDiffEq\c2Dwp\src\nlsolve\utils.jl:407
  ...
Stacktrace:
 [1] resize!(integrator::OrdinaryDiffEq.ODEIntegrator{Tsit5, true, VectorOfArray{Float64, 2, Vector{Vector{Float64}}}, Nothing, Float64, SciMLBase.NullParameters, Float64, Float64, Float64, Float64, Vector{VectorOfArray{Float64, 2, Vector{Vector{Float64}}}}, ODESolution{Float64, 3, Vector{VectorOfArray{Float64, 2, Vector{Vector{Float64}}}}, Nothing, Nothing, Vector{Float64}, Vector{Vector{VectorOfArray{Float64, 2, Vector{Vector{Float64}}}}}, ODEProblem{VectorOfArray{Float64, 2, Vector{Vector{Float64}}}, Tuple{Float64, Float64}, true, SciMLBase.NullParameters, ODEFunction{true, SciMLBase.AutoSpecialize, typeof(sysde!), UniformScaling{Bool}, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, 
Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, typeof(SciMLBase.DEFAULT_OBSERVED), Nothing, Nothing}, Base.Pairs{Symbol, Union{}, Tuple{}, NamedTuple{(), Tuple{}}}, SciMLBase.StandardODEProblem}, Tsit5, OrdinaryDiffEq.InterpolationData{ODEFunction{true, SciMLBase.AutoSpecialize, typeof(sysde!), UniformScaling{Bool}, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, typeof(SciMLBase.DEFAULT_OBSERVED), Nothing, Nothing}, Vector{VectorOfArray{Float64, 2, Vector{Vector{Float64}}}}, Vector{Float64}, Vector{Vector{VectorOfArray{Float64, 2, Vector{Vector{Float64}}}}}, OrdinaryDiffEq.Tsit5Cache{VectorOfArray{Float64, 2, Vector{Vector{Float64}}}, VectorOfArray{Float64, 2, Vector{Vector{Float64}}}, VectorOfArray{Float64, 2, Vector{Vector{Float64}}}, OrdinaryDiffEq.Tsit5ConstantCache{Float64, Float64}}}, DiffEqBase.DEStats}, ODEFunction{true, SciMLBase.AutoSpecialize, typeof(sysde!), UniformScaling{Bool}, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, typeof(SciMLBase.DEFAULT_OBSERVED), Nothing, Nothing}, OrdinaryDiffEq.Tsit5Cache{VectorOfArray{Float64, 2, Vector{Vector{Float64}}}, VectorOfArray{Float64, 2, Vector{Vector{Float64}}}, VectorOfArray{Float64, 2, Vector{Vector{Float64}}}, OrdinaryDiffEq.Tsit5ConstantCache{Float64, Float64}}, OrdinaryDiffEq.DEOptions{Float64, Float64, Float64, Float64, PIController{Rational{Int64}}, typeof(DiffEqBase.ODE_DEFAULT_NORM), typeof(opnorm), Nothing, CallbackSet{Tuple{}, Tuple{}}, typeof(DiffEqBase.ODE_DEFAULT_ISOUTOFDOMAIN), typeof(DiffEqBase.ODE_DEFAULT_PROG_MESSAGE), typeof(DiffEqBase.ODE_DEFAULT_UNSTABLE_CHECK), DataStructures.BinaryHeap{Float64, DataStructures.FasterForward}, DataStructures.BinaryHeap{Float64, DataStructures.FasterForward}, Nothing, Nothing, 
Int64, Tuple{}, Tuple{}, Tuple{}}, VectorOfArray{Float64, 2, Vector{Vector{Float64}}}, Float64, Nothing, OrdinaryDiffEq.DefaultInit}, i::Int64)
   @ OrdinaryDiffEq C:\Users\licer\.julia\packages\OrdinaryDiffEq\c2Dwp\src\integrators\integrator_interface.jl:123
 [2] top-level scope
   @

```

(If a fix is possible, I’d much prefer the `ElasticArray` approach since that (for whatever reason) works 10x faster than the `VectorOfArray` approach for my application.)

---

<div class="post-metadata">

**Author:** ![SteffenPL](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/steffenpl/32/206270_2.png) [@SteffenPL](https://discourse.julialang.org/u/SteffenPL)\
**Post date:** [October 31, 2022, 11:03pm UTC](https://discourse.julialang.org/t/resizing-ode-integrator-with-matrix-or-vectorofarray-initial-condition/89583/2 "2022-10-31T23:03:49Z")

</div>

I didn’t run any code, but could it be that you need to call `resize!` with two size arguments (e.g. for two-dimensional arrays instead of one-dimensional vectors)? For example `resize!(integrator, 2, 4)`, just guessing.

---

<div class="post-metadata">

**Author:** ![DanielVandH](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/danielvandh/32/31134_2.png) [@DanielVandH](https://discourse.julialang.org/u/DanielVandH)\
**Post date:** [October 31, 2022, 11:14pm UTC](https://discourse.julialang.org/t/resizing-ode-integrator-with-matrix-or-vectorofarray-initial-condition/89583/3 "2022-10-31T23:14:32Z")

</div>

I considered that initially, e.g.

```julia
resize!(integrator, (4, 5))
resize!(integrator, 4, 5)

```

Doesn’t work, unfortunately (stacktrace is essentially the same).

---

<div class="post-metadata">

**Author:** ![DanielVandH](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/danielvandh/32/31134_2.png) [@DanielVandH](https://discourse.julialang.org/u/DanielVandH)\
**Post date:** [November 1, 2022, 12:48am UTC](https://discourse.julialang.org/t/resizing-ode-integrator-with-matrix-or-vectorofarray-initial-condition/89583/4 "2022-11-01T00:48:05Z")

</div>

Actually, I think this is the solution - I should’ve been using

```julia
resize!(integrator, (2, i))

```

since `ElasticArrays` needs the number of rows in the first part of that tuple:

```julia
using OrdinaryDiffEq
using ElasticArrays
function sysde!(du, u, p, t)
    du[:, 1] .= rand(2)
    du[:, 2] .= rand(2)
    du[:, 3] .= rand(2)
    nothing 
end
u0 = ElasticArray{Float64}([0.0 0.0 0.0; 0.0 0.0 0.0])
tspan=(0.0,1.0)
prob=ODEProblem(sysde!, u0, tspan)
integrator = init(prob,Tsit5())
resize!(integrator, (2, 4)) # works

```

Not sure about the `VectorOfArray` case, but this works.