update_dependency_cache! performance bottleneck

[fonsp]

Here is a profile of changing the bond value of x (i.e. moving the Slider) in the PlutoUI sample notebook, which takes a surprisingly long time (90ms for me):

It shows that update_dependency_cache! is the bottleneck, taking about 2/3 of the total time. Since this is a non-essential feature, and because the topology does not change when running bonds, it should be possible to eliminate it.

bond value benchmark.jl.txt

[fonsp]

Maybe related, there are still lots of unresolved cells after running the notebook:

@Pangoraw

[fonsp]

#2077 fixed the unresolved_cells issue, which fixes the performance issue in sample/PlutoUI.jl.jl, because update_dependency_cache! is no longer begin called during set_bond_values_reactive! (here).

However, if any cells contains a macrocall that can not be resolved, then this issue becomes noticeable again. Notice that by removing @asdf (the only unresolved cell), performance increases again:

Schermopname.2022-04-29.om.16.28.51.mov

[Pangoraw]

Maybe we could use a != equality check here?

Pluto.jl/src/analysis/topological_order.jl

Line 100 in caf7326

if cached === nothing || cached.input_topology !== notebook.topology

[fonsp]

@Pangoraw I also traced back the problem to this point! I made #2079, which would be equivalent to your suggestion, right?

[fonsp]

#2079 This PR took out the first ⛰ in the profile:

New profile

[fonsp]

Fixed! Finishing my PR