setindex!: MethodError: Cannot `convert` an object of type Symbol to an object of type String

[iryabink]

I am using pmap to compute in parallel the result of application of the function ppoly(), which takes an array of strings and numbers of the same length. I manually chop these arrays into arrays of arrays, so that the call looks like

ps = pmap(ppoly, words_all_chunks, coeffs_all_chunks)

I do it multiple times with arguments of different lengths, but eventually, when chunks got big enough, Julia triggers a mysterious error:

ERROR: LoadError: On worker 4:
MethodError: Cannot `convert` an object of type Symbol to an object of type String
Closest candidates are:
  convert(::Type{String}, ::FortranFiles.FString{L}) where L at /home/ilya/.julia/packages/FortranFiles/BjZQn/src/string.jl:43 (method too new to be called from this world context.)
  convert(::Type{T<:AbstractString}, ::T<:AbstractString) where T<:AbstractString at strings/basic.jl:207
  convert(::Type{T<:AbstractString}, ::AbstractString) where T<:AbstractString at strings/basic.jl:208
  ...
setindex! at ./array.jl:769
deserialize_fillarray! at /buildworker/worker/package_linux64/build/usr/share/julia/stdlib/v1.0/Serialization/src/Serialization.jl:999
deserialize_array at /buildworker/worker/package_linux64/build/usr/share/julia/stdlib/v1.0/Serialization/src/Serialization.jl:991
handle_deserialize at /buildworker/worker/package_linux64/build/usr/share/julia/stdlib/v1.0/Serialization/src/Serialization.jl:749
deserialize at /buildworker/worker/package_linux64/build/usr/share/julia/stdlib/v1.0/Serialization/src/Serialization.jl:711
#1 at /buildworker/worker/package_linux64/build/usr/share/julia/stdlib/v1.0/Serialization/src/Serialization.jl:849
ntuple at ./tuple.jl:133
deserialize_tuple at /buildworker/worker/package_linux64/build/usr/share/julia/stdlib/v1.0/Serialization/src/Serialization.jl:849
handle_deserialize at /buildworker/worker/package_linux64/build/usr/share/julia/stdlib/v1.0/Serialization/src/Serialization.jl:741
deserialize at /buildworker/worker/package_linux64/build/usr/share/julia/stdlib/v1.0/Serialization/src/Serialization.jl:711
#1 at /buildworker/worker/package_linux64/build/usr/share/julia/stdlib/v1.0/Serialization/src/Serialization.jl:849
ntuple at ./tuple.jl:133
deserialize_tuple at /buildworker/worker/package_linux64/build/usr/share/julia/stdlib/v1.0/Serialization/src/Serialization.jl:849
handle_deserialize at /buildworker/worker/package_linux64/build/usr/share/julia/stdlib/v1.0/Serialization/src/Serialization.jl:741
deserialize_msg at /buildworker/worker/package_linux64/build/usr/share/julia/stdlib/v1.0/Serialization/src/Serialization.jl:711
#invokelatest#1 at ./essentials.jl:697 [inlined]
invokelatest at ./essentials.jl:696 [inlined]
message_handler_loop at /buildworker/worker/package_linux64/build/usr/share/julia/stdlib/v1.0/Distributed/src/process_messages.jl:160
process_tcp_streams at /buildworker/worker/package_linux64/build/usr/share/julia/stdlib/v1.0/Distributed/src/process_messages.jl:117
#105 at ./task.jl:259
Stacktrace:
 [1] (::getfield(Base, Symbol("##684#686")))(::Task) at ./asyncmap.jl:178
 [2] foreach(::getfield(Base, Symbol("##684#686")), ::Array{Any,1}) at ./abstractarray.jl:1835
 [3] maptwice(::Function, ::Channel{Any}, ::Array{Any,1}, ::Base.Iterators.Zip2{Array{Array{String,1},1},Array{Array{Float64,1},1}}) at ./asyncmap.jl:178
 [4] #async_usemap#669 at ./asyncmap.jl:154 [inlined]
 [5] #async_usemap at ./none:0 [inlined]
 [6] #asyncmap#668 at ./asyncmap.jl:81 [inlined]
 [7] #asyncmap at ./none:0 [inlined]
 [8] #pmap#213(::Bool, ::Int64, ::Nothing, ::Array{Any,1}, ::Nothing, ::Function, ::Function, ::WorkerPool, ::Base.Iterators.Zip2{Array{Array{String,1},1},Array{Array{Float64,1},1}}) at /buildworker/worker/package_linux64/build/usr/share/julia/stdlib/v1.0/Distributed/src/pmap.jl:126
 [9] pmap(::Function, ::WorkerPool, ::Base.Iterators.Zip2{Array{Array{String,1},1},Array{Array{Float64,1},1}}) at /buildworker/worker/package_linux64/build/usr/share/julia/stdlib/v1.0/Distributed/src/pmap.jl:101
 [10] #pmap#223(::Base.Iterators.Pairs{Union{},Union{},Tuple{},NamedTuple{(),Tuple{}}}, ::Function, ::Function, ::Base.Iterators.Zip2{Array{Array{String,1},1},Array{Array{Float64,1},1}}) at /buildworker/worker/package_linux64/build/usr/share/julia/stdlib/v1.0/Distributed/src/pmap.jl:156
 [11] pmap(::Function, ::Base.Iterators.Zip2{Array{Array{String,1},1},Array{Array{Float64,1},1}}) at /buildworker/worker/package_linux64/build/usr/share/julia/stdlib/v1.0/Distributed/src/pmap.jl:156
 [12] #pmap#224(::Base.Iterators.Pairs{Union{},Union{},Tuple{},NamedTuple{(),Tuple{}}}, ::Function, ::Function, ::Array{Array{String,1},1}, ::Array{Array{Float64,1},1}) at /buildworker/worker/package_linux64/build/usr/share/julia/stdlib/v1.0/Distributed/src/pmap.jl:157
 [13] pmap(::Function, ::Array{Array{String,1},1}, ::Array{Array{Float64,1},1}) at /buildworker/worker/package_linux64/build/usr/share/julia/stdlib/v1.0/Distributed/src/pmap.jl:157
 [14] #direct_interaction_space#31(::Float64, ::Bool, ::Function, ::PauliPolynomial, ::Array{Float64,1}, ::Array{Float64,1}) at ./util.jl:156
[15] (::getfield(Main, Symbol("#kw##direct_interaction_space")))(::NamedTuple{(:threshold, :verbose),Tuple{Float64,Bool}}, ::typeof(direct_interaction_space), ::PauliPolynomial, ::Array{Float64,1}, ::Array{Float64,1}) at ./none:0
 [16] #generate_entanglers#63(::String, ::UnitRange{Int64}, ::Array{Any,1}, ::Array{Any,1}, ::Function, ::PauliPolynomial, ::Array{Float64,1}, ::Array{Float64,1}) at aaa.jl:37
 [17] (::getfield(Main, Symbol("#kw##generate_entanglers")))(::NamedTuple{(:space, :rank),Tuple{String,UnitRange{Int64}}}, ::typeof(generate_entanglers), ::PauliPolynomial, ::Array{Float64,1}, ::Array{Float64,1}) at ./none:0
 [18] top-level scope at util.jl:156
 [19] top-level scope at bbb.jl:418
 [20] include at ./boot.jl:317 [inlined]
 [21] include_relative(::Module, ::String) at ./loading.jl:1044
 [22] include(::Module, ::String) at ./sysimg.jl:29
 [23] include(::String) at ./client.jl:392
 [24] top-level scope at none:0

Unfortunately, I cannot make a minimal reproducible example for that, but I suspect it might be related to a similar issue #30405 for getindex! --- some indexing variables are going out of range. Just for an idea how big chunks are:

length.(words_all_chunks) = [2560204, 2560204, 2560204, 2560204]
length.(coeffs_all_chunks) = [2560204, 2560204, 2560204, 2560204]

julia> versioninfo()
Julia Version 1.0.4
Commit 38e9fb7f80 (2019-05-16 03:38 UTC)
Platform Info:
  OS: Linux (x86_64-pc-linux-gnu)
  CPU: Intel(R) Xeon(R) CPU           X5675  @ 3.07GHz
  WORD_SIZE: 64
  LIBM: libopenlibm
  LLVM: libLLVM-6.0.0 (ORCJIT, westmere)

[hotarolag]

I'm facing same problem. Have you already fixed this?

[bblankrot]

I too am encountering this. Have either of you solved this cryptic error? To be clear, everything works when using a single process.

[iryabink]

Hi Boaz: No, I gave up. The situation for me is exactly like yours: single-process calculations work perfectly. What's the Julia version are you using? I didn't check the latest 1.2, may be the bug is fixed now. What we need is a good minimal reproducible example. Could you think of something? All my cases are hard to distill. Thanks, Ilya

…

On Thu, Nov 7, 2019 at 1:55 AM Boaz Blankrot ***@***.***> wrote: I too am encountering this. Have either of you solved this cryptic error? To be clear, everything works when using a single process. — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub <#32157?email_source=notifications&email_token=AMF2PZKL3PLXJ2V2G4QWEYLQSO3XLA5CNFSM4HP6BTZKYY3PNVWWK3TUL52HS4DFVREXG43VMVBW63LNMVXHJKTDN5WW2ZLOORPWSZGOEDLF6JI#issuecomment-550919973>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AMF2PZNUXKND44UYHRHHOADQSO3XLANCNFSM4HP6BTZA> .

[bblankrot]

I've had this happen in both Julia 1.1.1 and 1.2.0. No luck reducing the example so far (simple functions all work), but I will continue trying.

[fargolo]

Same problem for me. Parallel computation breaking it.

[Prashantmdgl9]

I was trying to run the Flux tutorial and I get something similar
using CSV, DataFrames

apples = CSV.File(datapath("data/apples.dat"))
apples = DataFrame(CSV.File(datapath("data/apples.dat")))

Both of them yield the same error:

MethodError: Cannot convert an object of type Bool to an object of type String
Closest candidates are:
convert(::Type{String}, !Matched::LLVM.MetadataAsValue) at /Users/prashantmudgal/.julia/packages/LLVM/5PewI/src/core/metadata.jl:19
convert(::Type{String}, !Matched::LLVM.DataLayout) at /Users/prashantmudgal/.julia/packages/LLVM/5PewI/src/datalayout.jl:27
convert(::Type{String}, !Matched::LLVM.Module) at /Users/prashantmudgal/.julia/packages/LLVM/5PewI/src/ir.jl:23
...
push!(::Array{String,1}, ::Bool) at array.jl:913
Parsers.Options(::Missing, ::UInt8, ::UInt8, ::UInt8, ::UInt8, ::UInt8, ::UInt8, ::UInt8, ::Nothing, ::Nothing, ::Nothing, ::Bool, ::Bool, ::Bool, ::Bool, ::Bool, ::Bool, ::Bool) at Parsers.jl:99
Parsers.Options(::Missing, ::UInt8, ::UInt8, ::UInt8, ::UInt8, ::UInt8, ::UInt8, ::UInt8, ::Nothing, ::Nothing, ::Nothing, ::Bool, ::Bool, ::Bool, ::Bool, ::Bool) at Parsers.jl:62
file(::String, ::Int64, ::Bool, ::Int64, ::Nothing, ::Int64, ::Int64, ::Bool, ::Nothing, ::Bool, ::Bool, ::Array{String,1}, ::String, ::Nothing, ::Bool, ::Char, ::Nothing, ::Nothing, ::Char, ::Nothing, ::UInt8, ::Nothing, ::Nothing, ::Nothing, ::Nothing, ::Dict{Int8,Int8}, ::Bool, ::Float64, ::Bool, ::Bool, ::Nothing, ::Bool, ::Bool, ::Nothing) at CSV.jl:381
CSV.File(::String; header::Int64, normalizenames::Bool, datarow::Int64, skipto::Nothing, footerskip::Int64, limit::Int64, transpose::Bool, comment::Nothing, use_mmap::Bool, ignoreemptylines::Bool, missingstrings::Array{String,1}, missingstring::String, delim::Nothing, ignorerepeated::Bool, quotechar::Char, openquotechar::Nothing, closequotechar::Nothing, escapechar::Char, dateformat::Nothing, decimal::UInt8, truestrings::Nothing, falsestrings::Nothing, type::Nothing, types::Nothing, typemap::Dict{Int8,Int8}, categorical::Bool, pool::Float64, strict::Bool, silencewarnings::Bool, threaded::Nothing, debug::Bool, parsingdebug::Bool, allowmissing::Nothing) at CSV.jl:260
CSV.File(::String) at CSV.jl:260
top-level scope at julia.jl:30

[mb4941]

Same problem. No one seems to know the solution.

[StefanKarpinski]

No one has provided a reproducible example here, which makes this issue non-actionable. It's highly unlikely that all of these convert problems are the same issue, and these are much more likely to be library issues than language issues. Accordingly, I'm closing this.