Fix performance of Containers.rowtable

[odow]

Closes #3404.

Julia 1.6

julia> using JuMP.Containers

julia> Containers.@container(x[i=1:100, j=1:50], i + j);

julia> function foo(x, header)
           names = tuple(header...)
           return [NamedTuple{names}((args..., x[i])) for (i, args) in Containers._rows(x)]
       end
foo (generic function with 1 method)

julia> function bar(x, header)
           elements = [(args..., x[i]) for (i, args) in Containers._rows(x)]
           return NamedTuple{tuple(header...)}.(elements)
       end
bar (generic function with 1 method)

julia> @assert foo(x, [:i, :j, :k]) == bar(x, [:i, :j, :k])

julia> @time foo(x, [:i, :j, :k]);
  0.006314 seconds (30.02 k allocations: 1.597 MiB)

julia> @time bar(x, [:i, :j, :k]);
  0.000154 seconds (23 allocations: 502.297 KiB)

Julia 1.9

julia> using JuMP.Containers

julia> Containers.@container(x[i=1:100, j=1:50], i + j);

julia> function foo(x, header)
           names = tuple(header...)
           return [NamedTuple{names}((args..., x[i])) for (i, args) in Containers._rows(x)]
       end
foo (generic function with 1 method)

julia> function bar(x, header)
           elements = [(args..., x[i]) for (i, args) in Containers._rows(x)]
           return NamedTuple{tuple(header...)}.(elements)
       end
bar (generic function with 1 method)

julia> @assert foo(x, [:i, :j, :k]) == bar(x, [:i, :j, :k])

julia> @time foo(x, [:i, :j, :k]);
  0.378728 seconds (140.02 k allocations: 5.545 MiB)

julia> @time bar(x, [:i, :j, :k]);
  0.000079 seconds (18 allocations: 482.516 KiB)

I don't understand the reason for the regression in 1.9. But this is better regardless.

[codecov]

Codecov Report

Patch coverage: 100.00% and no project coverage change.

Comparison is base (19ab5d6) 98.05% compared to head (763d625) 98.05%.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #3410   +/-   ##
=======================================
  Coverage   98.05%   98.05%           
=======================================
  Files          34       34           
  Lines        4926     4926           
=======================================
  Hits         4830     4830           
  Misses         96       96           

Impacted Files	Coverage Δ
src/Containers/tables.jl	100.00% <100.00%> (ø)

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[odow]

Just to close the loop on the original benchmark:

Previously

julia> @btime JuMP.Containers.rowtable($value, $x, header=$header);
  371.580 ms (210016 allocations: 7.07 MiB)

julia> @btime test($value, $x, header=$header);
  6.915 ms (105016 allocations: 3.03 MiB)

julia> @btime JuMP.Containers.rowtable($value, $y, header=$header);
  187.218 ms (105010 allocations: 3.41 MiB)

julia> @btime test($value, $y, header=$header);
  3.433 ms (52510 allocations: 1.39 MiB)

This PR

julia> @btime JuMP.Containers.rowtable(value, $x, header=$header);
  2.349 ms (55025 allocations: 1.46 MiB)

julia> @btime test(value, $x, header=$header);
  6.906 ms (105016 allocations: 3.03 MiB)

julia> @btime JuMP.Containers.rowtable(value, $y, header=$header);
  1.211 ms (27518 allocations: 625.70 KiB)

julia> @btime test(value, $y, header=$header);
  3.354 ms (52510 allocations: 1.39 MiB)