I posted an issue
<https://github.com/JuliaParallel/DistributedArrays.jl/issues/7> on the
DArrays repo but someone in IRC suggested opening a thread here as well.
I'm seeing different results from map vs pmap on a DArray in Julia
0.4.0-dev+3844 on Linux. When I run, on 6 procs:
julia> testa = drand(36)
36-element DistributedArrays.DArray{Float64,1,Array{Float64,1}}:
0.636737
0.275769
0.961624
0.427848
0.668537
0.0215699
0.292591
0.487622
0.54222
0.579438
0.299413
0.0699156
0.985861
0.642223
0.0108336
0.466572
0.134984
0.0718047
0.600704
0.367337
0.722101
0.96763
0.427482
0.963513
0.467348
0.987774
0.773584
0.531576
0.0155698
0.383172
0.0347603
0.299581
0.0226568
0.687901
0.22271
0.238291
julia> testb = drand(36)
36-element DistributedArrays.DArray{Float64,1,Array{Float64,1}}:
0.933919
0.445692
0.0028197
0.722083
0.088373
0.820338
0.71782
0.972424
0.623399
0.157076
0.657007
0.0753378
0.712683
0.303925
0.591726
0.320129
0.5457
0.00830437
0.0753483
0.973917
0.171903
0.291315
0.875653
0.0619788
0.53868
0.069952
0.534305
0.798335
0.923633
0.239445
0.748613
0.00554521
0.650063
0.770877
0.237519
0.414616
julia> pmap( (x) -> (x*x), testa)
175-element Array{Any,1}:
0.405433
0.405433
0.405433
0.405433
0.405433
0.405433
0.0760486
0.0760486
0.0760486
0.0760486
0.0760486
0.0760486
0.92472
0.92472
0.92472
0.183054
0.183054
0.183054
0.92472
0.183054
0.183054
0.183054
0.446942
0.446942
0.446942
0.446942
0.000465259
0.446942
⋮
0.00120828
0.00120828
0.00120828
0.00120828
0.00120828
0.00120828
0.0897485
0.0897485
0.0897485
0.0897485
0.0897485
0.000513332
0.000513332
0.473207
0.000513332
0.000513332
0.473207
0.473207
0.473207
0.0495998
0.473207
0.0495998
0.0495998
0.0495998
0.0567826
0.0567826
0.0567826
0.0567826
julia> map( (x) -> (x*x), testb)
36-element DistributedArrays.DArray{Float64,1,Array{Float64,1}}:
0.872205
0.198641
7.95072e-6
0.521403
0.00780978
0.672954
0.515266
0.945609
0.388626
0.0246728
0.431658
0.00567578
0.507917
0.0923703
0.35014
0.102483
0.297789
6.89625e-5
0.00567737
0.948514
0.0295506
0.0848642
0.766769
0.00384137
0.290177
0.00489328
0.285482
0.637339
0.853098
0.0573337
0.560421
3.07494e-5
0.422581
0.594251
0.0564152
0.171907
My intuition is that pmap and map on a DArray should do the same thing, and
they did in 0.3.6. Searching through the source for DArrays, it appears I'm
only supposed to use map? Which is fine, but should there be a note in the docs
about it?
