Out of memory error caused by calling @btime on on a medium sized model

[DoktorMike]

I define the following function which requires some memory and call it twice with btime which results in an out of memory error. Code given below:

using Flux
using Flux.Tracker
using BenchmarkTools

function fluxderivtest(nhidden=100_000, ninput=1_000)
    W = param(rand(nhidden, ninput) .- 0.5)
    b = param(rand(nhidden) .- 0.5)
    x = rand(ninput)
    f(x) = tanh(sum(W*x .+ b))
    g = Tracker.gradient(() -> f(x), Params([W, b]))
    g[W], g[b]
end

@btime fluxderivtest()
@btime fluxderivtest()

which results in the following error:

ERROR: OutOfMemoryError()
Stacktrace:
 [1] Type at ./boot.jl:396 [inlined]
 [2] similar at ./array.jl:328 [inlined]
 [3] zero at ./abstractarray.jl:827 [inlined]
 [4] Type at /home/michael/.julia/packages/Flux/UHjNa/src/tracker/array.jl:30 [inlined]
 [5] param(::Array{Float64,2}) at /home/michael/.julia/packages/Flux/UHjNa/src/tracker/Tracker.jl:105
 [6] fluxderivtest(::Int64, ::Int64) at ./REPL[4]:2 (repeats 2 times)
 [7] ##core#372() at /home/michael/.julia/packages/BenchmarkTools/dtwnm/src/execution.jl:293
 [8] ##sample#373(::BenchmarkTools.Parameters) at /home/michael/.julia/packages/BenchmarkTools/dtwnm/src/execution.jl:301
 [9] sample at /home/michael/.julia/packages/BenchmarkTools/dtwnm/src/execution.jl:316 [inlined]
 [10] #_lineartrial#20(::Int64, ::Base.Iterators.Pairs{Union{},Union{},Tuple{},NamedTuple{(),Tuple{}}}, ::Function, ::BenchmarkTools.Benchmark{Symbol("##benchmark#371")}, ::BenchmarkTools.Parameters) at /home/michael/.julia/packages/BenchmarkTools/dtwnm/src/execution.jl:71
 [11] _lineartrial(::BenchmarkTools.Benchmark{Symbol("##benchmark#371")}, ::BenchmarkTools.Parameters) at /home/michael/.julia/packages/BenchmarkTools/dtwnm/src/execution.jl:63
 [12] #invokelatest#1 at ./essentials.jl:686 [inlined]
 [13] invokelatest at ./essentials.jl:685 [inlined]
 [14] #lineartrial#17 at /home/michael/.julia/packages/BenchmarkTools/dtwnm/src/execution.jl:33 [inlined]
 [15] lineartrial at /home/michael/.julia/packages/BenchmarkTools/dtwnm/src/execution.jl:33 [inlined]
 [16] #tune!#23(::Bool, ::String, ::Base.Iterators.Pairs{Union{},Union{},Tuple{},NamedTuple{(),Tuple{}}}, ::Function, ::BenchmarkTools.Benchmark{Symbol("##benchmark#371")}, ::BenchmarkTools.Parameters) at /home/michael/.julia/packages/BenchmarkTools/dtwnm/src/execution.jl:135
 [17] tune! at /home/michael/.julia/packages/BenchmarkTools/dtwnm/src/execution.jl:134 [inlined] (repeats 2 times)
 [18] top-level scope at /home/michael/.julia/packages/BenchmarkTools/dtwnm/src/execution.jl:388

Versioninfo:

Julia Version 1.0.0
Commit 5d4eaca (2018-08-08 20:58 UTC)
Platform Info:
OS: Linux (x86_64-pc-linux-gnu)
CPU: Intel(R) Core(TM) i7-6650U CPU @ 2.20GHz
WORD_SIZE: 64
LIBM: libopenlibm
LLVM: libLLVM-6.0.0 (ORCJIT, skylake)

I'm running Ubuntu 18.04 on a Surface pro 4 with 16GB of RAM.

Also asked a question regarding this on discourse: (https://discourse.julialang.org/t/how-do-i-release-flux-tracker-allocated-memory/14663)

As I understand the Garbage collection should take care of this but in my case it doesn't unless I'm doing something I shouldn't be doing of course.

[oscardssmith]

@chflood should we add this to the GC benchmark repo?

[ViralBShah]

We no longer have Tracker in Flux