Discretization of brussellator fails

[finmod]

In the two versions of brusselator.jl (test and docs), the discretization cell goes into a loop and never exit

# Method of lines discretization
N = 32

dx = 1 / N
dy = 1 / N

order = 2

discretization = MOLFiniteDifference([x => dx, y => dy], t, approx_order = order)

#MethodOfLines.generate_code(pdesys, discretization)
# Convert the PDE problem into an ODE problem
println("Discretization:")
@time prob = discretize(pdesys, discretization)

time 87 m and counting!

It is advisable to have this "Getting Started example" always in top form otherwise using MOL is a curse.

[ChrisRackauckas]

@AayushSabharwal I thought this was fixed on latest releases already?

[AayushSabharwal]

I'll take a look

[AayushSabharwal]

On MTK#master

396.630006 seconds (4.36 G allocations: 137.717 GiB, 2.21% gc time, 1.41% compilation time: 47% of which was recompilation)

[finmod]

Here is the outcome of a test of brusselator_eq.jl on my notebook. Yes, it works in 144 minutes. This cannot be a gentle or "Getting started" introduction to MOL! Or is there a problem with all these warnings?

Test Summary: | Pass Total Time
MOLFiniteDifference Interface | 102 102 5m35.8s
335.806247 seconds (1.36 G allocations: 44.751 GiB, 2.50% gc time, 34.16% compilation time)
Discretization:
┌ Warning: The system contains interface boundaries, which are not compatible with system transformation. The system will not be transformed. Please post an issue if you need this feature.
└ @ MethodOfLines C:\Users\Denis.julia\packages\MethodOfLines\QMJYo\src\system_parsing\pde_system_transformation.jl:43
1205.361398 seconds (4.94 G allocations: 156.575 GiB, 1.93% gc time, 0.30% compilation time)
Solve:
7318.014306 seconds (853.49 M allocations: 32.619 GiB, 0.29% gc time, 94.88% compilation time)
WARNING: Method definition brusselator_f(Any, Any, Any) in module ##238 at C:\Users\Denis.julia\packages\MethodOfLines\QMJYo\test\pde_systems\brusselator_eq.jl:18 overwritten at C:\Users\Denis.julia\packages\MethodOfLines\QMJYo\test\pde_systems\brusselator_eq.jl:72.
Test Summary: | Pass Total Time
MOLFiniteDifference Interface: 2D Brusselator Equation | 1154 1154 144m21.7s
8661.909559 seconds (6.83 G allocations: 219.594 GiB, 0.57% gc time, 80.36% compilation time)
Test Summary: | Pass Total Time
MOLFiniteDifference Interface: 1D Linear Diffusion, Non-Uniform | 96 96 6m39.0s
399.000078 seconds (1.07 G allocations: 37.390 GiB, 1.92% gc time, 57.19% compilation time)
Test Summary: | Broken Total Time
MOLFiniteDifference Interface: Advanced Nonlinear Diffusion | 1 1 20.5s
20.518313 seconds (21.37 M allocations: 1.013 GiB, 1.08% gc time, 96.35% compilation time)
┌ Warning: The system contains interface boundaries, which are not compatible with system transformation. The system will not be transformed. Please post an issue if you need this feature.
└ @ MethodOfLines C:\Users\Denis.julia\packages\MethodOfLines\QMJYo\src\system_parsing\pde_system_transformation.jl:43

[AayushSabharwal]

The tests aren't the getting started introduction though? And the long execution time issue is fixed on the latest MTK.

[finmod]

For completeness, the Getting Started introduction remains a huge drag to using MOL:

# Method of lines discretization
N = 32

dx = 1 / N
dy = 1 / N

order = 2

discretization = MOLFiniteDifference([x => dx, y => dy], t, approx_order = order)

#MethodOfLines.generate_code(pdesys, discretization)
# Convert the PDE problem into an ODE problem
println("Discretization:")
@time prob = discretize(pdesys, discretization)
26 m

gives this outcome which is still 4x larger thhan your quote above:

�[33m�[1m┌ �[22m�[39m�[33m�[1mWarning: �[22m�[39mThe system contains interface boundaries, which are not compatib`le with system transformation. The system will not be transformed. Please post an issue if you need this feature.
�[33m�[1m└ �[22m�[39m�[90m@ MethodOfLines C:\Users\Denis\.julia\packages\MethodOfLines\QMJYo\src\system_parsing\pde_system_transformation.jl:43�[39m
1556.288325 seconds (4.94 G allocations: 155.908 GiB, 1.73% gc time, 0.95% compilation time: 59% of which was recompilation)

[ChrisRackauckas]

v10.6.0?

[finmod]

MTK v9.80.6 and MOL v0.11.8

[AayushSabharwal]

Right, so v9 being slow is known. When I said that this is fixed on the latest MTK, I was referring to v10.6. Some of the performance improvements that make it faster on 10.6 are backported to v9 in SciML/ModelingToolkit.jl#3771 which just merged and will be tagged soon. Note that it probably won't be as fast as v10, because not all of the changes can be backported.

[AayushSabharwal]

It's also worth noting that performance numbers vary drastically across machines, so my @times likely won't be the same as yours.

[finmod]

Ok got the hint. I am reinstalling MTK#Master and rebuilding everything else around it.

[AayushSabharwal]

If you'd like to try the latest v9, it's available in the backport-v9 branch.

[finmod]

With backport-v9, no notable improvement. I will just wait until MTKv10.6 appears in my status.