Change map for a for loop

[andreasnoack]

to work around JuliaLang/julia#35800

which can cause very slow compile times in Julia 1.6. In Pumas, this change alone had the following effect on a single function call:

Before:

40.194758 seconds (83.73 M allocations: 6.623 GiB, 2.70% gc time, 99.99% compilation time)

After

2.916390 seconds (7.31 M allocations: 446.180 MiB, 3.71% gc time, 99.96% compilation time)

I'm erroring out in the empty case since it avoids the problem of determining the return type. I'd think that it's expected that the number of trajectories is positive. I actually think that part of the problem with map is that it has to consider the empty case but that is mostly speculation.

[codecov]

Codecov Report

Merging #45 (b3ea422) into master (3150439) will increase coverage by 0.12%.
The diff coverage is 87.50%.

@@            Coverage Diff            @@
##           master     #45      +/-   ##
=========================================
+ Coverage    9.66%   9.78%   +0.12%     
=========================================
  Files          39      39              
  Lines        2826    2830       +4     
=========================================
+ Hits          273     277       +4     
  Misses       2553    2553              

Impacted Files	Coverage Δ
src/ensemble/basic_ensemble_solve.jl	26.22% <87.50%> (+2.50%)	⬆️

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[ChrisRackauckas]

Seriously 😱?

[andreasnoack]

Yes. It's really sad.

[korsbo]

Ickie ickie! You're even growing an array and it's still much faster - before 1.6 I would have been on the hunt to do the exact opposite changes to my code 😢