Unexpected Errors using 'prod()' when specifying 'dims = _' argument on matrices of Unitful values

[jmtlawrie]

Hello,

today I observed a couple of unexpected behaviours using the Unitful.jl package - I'm not sure what to make of them, since it is quite easy to work around the errors as seen in the MWE below. Nevertheless, I thought it would still be worth sharing.

I have included the stack traces below the MWE for both the DimensionError and the ArgumentError.

In the case of the DimensionError, this seems on the surface to be similar to #585.

In the case of the ArgumentError, I'm confused at this behaviour and I haven't seen anything similar in the other issues (I might have missed something, though).

Thanks for your time.

J

---

MWE

using Unitful

A = [1 2; 3 4]

prod(A) # 24
A[1, :] .* A[2, :] # [3, 8]
prod(A; dims = 1) # [3, 8]

B = A .* u"m"

prod(B) # 24 m⁴
B[1, :] .* B[2, :] # [3 m², 8 m²]
prod(B; dims = 1) # DimensionError:  and m² are not dimensionally compatible.

C = A .* [u"m" u"m"; u"kg" u"kg"]

prod(C) # 24 kg² m²
C[1, :] .* C[2, :] # [3 kg m, 8 kg m]
prod(C; dims = 1) # ArgumentError: zero(Quantity{Int64}) not defined.

---

Version information

Unitful:

Status `~/.julia/environments/v1.9/Project.toml`
  [1986cc42] Unitful v1.19.0

julia> versioninfo()
Julia Version 1.9.4
Commit 8e5136fa297 (2023-11-14 08:46 UTC)
Build Info:
  Official https://julialang.org/ release
Platform Info:
  OS: macOS (x86_64-apple-darwin22.4.0)
  CPU: 4 × Intel(R) Core(TM) i5-5250U CPU @ 1.60GHz
  WORD_SIZE: 64
  LIBM: libopenlibm
  LLVM: libLLVM-14.0.6 (ORCJIT, broadwell)
  Threads: 1 on 4 virtual cores
Environment:
  JULIA_EDITOR = code
  JULIA_NUM_THREADS = 

---

Stacktraces

DimensionError

ERROR: DimensionError:  and m² are not dimensionally compatible.
Stacktrace:
  [1] #s103#141
    @ ~/.julia/packages/Unitful/R4J37/src/conversion.jl:7 [inlined]
  [2] var"#s103#141"(::Any, s::Any, t::Any)
    @ Unitful ./none:0
  [3] (::Core.GeneratedFunctionStub)(::Any, ::Vararg{Any})
    @ Core ./boot.jl:602
  [4] uconvert(a::Unitful.FreeUnits{(), NoDims, nothing}, x::Quantity{Int64, 𝐋², Unitful.FreeUnits{(m²,), 𝐋², nothing}})
    @ Unitful ~/.julia/packages/Unitful/R4J37/src/conversion.jl:72
  [5] convert(#unused#::Type{Int64}, y::Quantity{Int64, 𝐋², Unitful.FreeUnits{(m²,), 𝐋², nothing}})
    @ Unitful ~/.julia/packages/Unitful/R4J37/src/conversion.jl:139
  [6] setindex!
    @ ./array.jl:971 [inlined]
  [7] setindex!
    @ ./multidimensional.jl:670 [inlined]
  [8] _mapreducedim!(f::typeof(identity), op::typeof(Base.mul_prod), R::Matrix{Int64}, A::Matrix{Quantity{Int64, 𝐋, Unitful.FreeUnits{(m,), 𝐋, nothing}}})
    @ Base ./reducedim.jl:311
  [9] mapreducedim!(f::Function, op::Function, R::Matrix{Int64}, A::Matrix{Quantity{Int64, 𝐋, Unitful.FreeUnits{(m,), 𝐋, nothing}}})
    @ Base ./reducedim.jl:324
 [10] _mapreduce_dim(f::Function, op::Function, #unused#::Base._InitialValue, A::Matrix{Quantity{Int64, 𝐋, Unitful.FreeUnits{(m,), 𝐋, nothing}}}, dims::Int64)
    @ Base ./reducedim.jl:371
 [11] #mapreduce#801
    @ ./reducedim.jl:357 [inlined]
 [12] mapreduce
    @ ./reducedim.jl:357 [inlined]
 [13] #_prod#839
    @ ./reducedim.jl:1023 [inlined]
 [14] _prod
    @ ./reducedim.jl:1023 [inlined]
 [15] #_prod#838
    @ ./reducedim.jl:1022 [inlined]
 [16] _prod
    @ ./reducedim.jl:1022 [inlined]
 [17] #prod#812
    @ ./reducedim.jl:994 [inlined]
 [18] top-level scope

ArgumentError

ERROR: ArgumentError: zero(Quantity{Int64}) not defined.
Stacktrace:
  [1] zero(x::Type{Quantity{Int64}})
    @ Unitful ~/.julia/packages/Unitful/R4J37/src/quantities.jl:363
  [2] _reducedim_init(f::typeof(identity), op::typeof(Base.mul_prod), fv::typeof(one), fop::typeof(prod), A::Matrix{Quantity{Int64}}, region::Int64)
    @ Base ./reducedim.jl:116
  [3] reducedim_init(f::Function, op::typeof(Base.mul_prod), A::Matrix{Quantity{Int64}}, region::Int64)
    @ Base ./reducedim.jl:111
  [4] _mapreduce_dim(f::Function, op::Function, #unused#::Base._InitialValue, A::Matrix{Quantity{Int64}}, dims::Int64)
    @ Base ./reducedim.jl:371
  [5] #mapreduce#801
    @ ./reducedim.jl:357 [inlined]
  [6] mapreduce
    @ ./reducedim.jl:357 [inlined]
  [7] #_prod#839
    @ ./reducedim.jl:1023 [inlined]
  [8] _prod
    @ ./reducedim.jl:1023 [inlined]
  [9] #_prod#838
    @ ./reducedim.jl:1022 [inlined]
 [10] _prod
    @ ./reducedim.jl:1022 [inlined]
 [11] #prod#812
    @ ./reducedim.jl:994 [inlined]
 [12] top-level scope

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