map and mapreduce

[mcabbott]

This should make map(f, A, B, C), and mapreduce(f, op, A, B, C) work for FillArrays.

One motivation is that Base's mapreduce isn't fast for multiple arrays, but if we peel off the ones which are Fill then we can go the fast path. The other is that a mix of CuArrays & Fill seems to give errors:

julia> mapreduce((x,y) -> x*conj(y), +, Fill(1.0, 3), cu(ones(3)))
ERROR: scalar getindex is disallowed

Edit -- scope has crept a little, it now also handles reduce, which has this result:

julia> sum(Fill(3,4,5), dims=1)
1×5 Matrix{Int64}:  # master
 12  12  12  12  12

1×5 Fill{Int64}: entries equal to 12  # this PR

Happy to remove / separate that if you prefer.

[mcabbott]

Error on 1.0 was real, "UndefVarError: _InitialValue not defined".

I've just disabled these methods on old versions, rather than try to figure out how 1.0 did this & exactly when the change happened. Without them you will more often get an Array, as you do without this PR.

[codecov]

Codecov Report

Merging #146 (0b68d40) into master (a7ce2f8) will increase coverage by 0.31%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #146      +/-   ##
==========================================
+ Coverage   95.66%   95.97%   +0.31%     
==========================================
  Files           4        4              
  Lines         531      572      +41     
==========================================
+ Hits          508      549      +41     
  Misses         23       23              

Impacted Files	Coverage Δ
src/FillArrays.jl	94.27% <ø> (ø)
src/fillbroadcast.jl	97.45% <100.00%> (+1.35%)	⬆️

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[dlfivefifty]

Tests are failing on 1.0

[mcabbott]

Oh right, sorry, looks like vararg mapreduce didn't exist at all then. Will omit those bits.

[mcabbott]

Bump?

[dlfivefifty]

Great if you bump the version number I can tag a new release

[mcabbott]

Can do, or else #144 has a version bump, too.