Bug using maximum

[tomerarnon]

When a vector of a variables gets too big (exactly 16 long for some reason...) maximum throws an error:

julia> u = [Variable(2) for j in 1:15];

julia> maximum(norm.(u));
# works fine

julia> u = [Variable(2) for j in 1:16];

julia> maximum(norm.(u));
ERROR: TypeError: non-boolean (EqConstraint) used in boolean context
Stacktrace:
 [1] mapreduce_impl(::typeof(identity), ::typeof(max), ::Array{EucNormAtom,1}, ::Int64, ::Int64) at ./reduce.jl:460
 [2] _mapreduce(::typeof(identity), ::typeof(max), ::IndexLinear, ::Array{EucNormAtom,1}) at ./reduce.jl:318
 [3] _mapreduce_dim at ./reducedim.jl:305 [inlined]
 [4] #mapreduce#537 at ./reducedim.jl:301 [inlined]
 [5] mapreduce at ./reducedim.jl:301 [inlined]
 [6] _maximum at ./reducedim.jl:650 [inlined]
 [7] _maximum at ./reducedim.jl:649 [inlined]
 [8] #maximum#543 at ./reducedim.jl:645 [inlined]
 [9] maximum(::Array{EucNormAtom,1}) at ./reducedim.jl:645
 [10] top-level scope at none:0

[ararslan]

I'm going to take a wild guess and say that this is where the 16 cutoff comes from:
https://github.com/JuliaLang/julia/blob/v1.1.0/base/reduce.jl#L309

[ararslan]

We can work around it here in this package by defining a custom mapreduce_impl specialized on arrays of AbstractExprs, but for discussion of a more general solution, I've opened JuliaLang/julia#31390.

[ararslan]

This actually works as expected on Julia master (1.2-DEV).

[tomerarnon]

Interesting! Glad to hear it works. The hacky way I got around the error was with max(u...), which worked just fine.

[odow]

Closing as fixed:

julia> maximum(norm.([Variable(2) for j in 1:1000]))
norm2 (convex; positive)
└─ 2-element real variable (id: 142…470)

julia> maximum(norm.([Variable(2) for j in 1:10000]))
norm2 (convex; positive)
└─ 2-element real variable (id: 125…703)

julia> maximum(norm.([Variable(2) for j in 1:100000]))
norm2 (convex; positive)
└─ 2-element real variable (id: 181…041)

julia> maximum(norm.([Variable(2) for j in 1:1000000]))
norm2 (convex; positive)
└─ 2-element real variable (id: 104…115)