Remove precompile statements

[odow]

These were once necessary, but now they're doing more harm than good.

The precompile_model functions are safe to replace with a warning because they have no user-visible effect.

Code

using JuMP, HiGHS
model = Model(HiGHS.Optimizer)
set_silent(model)
@variable(model, x >= 0)
@variable(model, 0 <= y <= 3)
@objective(model, Min, 12x + 20y)
@constraint(model, c1, 6x + 8y >= 100)
@constraint(model, c2, 7x + 12y >= 120)
optimize!(model)

Before

(base) oscar@MacBookPro precompile % time julia --project=. main.jl
julia --project=. main.jl  2.73s user 0.45s system 101% cpu 3.119 total
(base) oscar@MacBookPro precompile % time julia --project=. main.jl
julia --project=. main.jl  2.76s user 0.41s system 101% cpu 3.111 total
(base) oscar@MacBookPro precompile % time julia --project=. main.jl
julia --project=. main.jl  2.73s user 0.41s system 102% cpu 3.077 total

This PR

(base) oscar@MacBookPro precompile % time julia --project=. main.jl            
julia --project=. main.jl  2.24s user 0.42s system 101% cpu 2.623 total
(base) oscar@MacBookPro precompile % time julia --project=. main.jl
julia --project=. main.jl  2.24s user 0.37s system 102% cpu 2.560 total
(base) oscar@MacBookPro precompile % time julia --project=. main.jl
julia --project=. main.jl  2.28s user 0.39s system 102% cpu 2.620 total

There are also now better tools like PrecompileTools.jl so that we can actually build and solve problems in each package if needed.

[blegat]

JuMP and HiGHS both have precompile statements so that's a bit misleading. Maybe also include benchmarks with pure-MOI and a solver that does not have precompile statemtents

[odow]

@blegat: we don't build this model anymore in JuMP, so these weren't actually being used.

[odow]

Arguably, this could make TTFS slower for new versions of MOI and an old version of Julia like 1.6.

For other solvers: we should improve them (if needed) by adding PrecompileTools to their packages. Not to MOI.

I don't think any package was actually using MOI.Utilities.precompile_model anyway.

[odow]

Here's SCS:

Old

julia --project=old scs.jl  13.78s user 0.57s system 100% cpu 14.327 total
julia --project=old scs.jl  13.80s user 0.54s system 100% cpu 14.336 total

New

julia --project=. scs.jl  13.80s user 0.53s system 99% cpu 14.329 total
julia --project=. scs.jl  13.80s user 0.51s system 100% cpu 14.285 total

There's no PrecompileTools, and these existing recompilation statements did not help because we've switched the type that JuMP uses.

I guess the action item in addition to this PR is to add precompilation things to each solver package.

[blegat]

Arguably, this could make TTFS slower for new versions of MOI and an old version of Julia like 1.6.

I don't think we should be worried about users not using the LTS.

For other solvers: we should improve them (if needed) by adding PrecompileTools to their packages. Not to MOI.

Yes, I just thought it would be useful to get a sense of whether users would notice a regression in the meantime. Looking at your SCS benchmark, it seems fine.