Apparent Issue with Precompilation for Dependent Packages about dynamicquantities.jl HOT 6 CLOSED

Hi @cadojo,

Thanks for the report. Excited to hear about the package you are making!

Is this Julia 1.10? Does it go away on Julia 1.9?

One thing to note is that the SymbolicDimensions symbols (e.g., us"m") don’t exist during precompilation. The reason for this is that there are so many, it makes startup time slow unless you are using them. So I wonder if it’s related to that.

Best,
Miles

from dynamicquantities.jl.

The quick fix would be to change

+ flux_distance(m, M) = 10^((m - M + 5) // 5) * u"Constants.pc"
- flux_distance(m, M) = 10^((m - M + 5) // 5) * us"Constants.pc"

us (SymbolicDimensions) is intended to be for display, whereas u (Dimensions) is intended to be for calculations.

us would not be available during precompilation because the variables are created upon first call. But maybe we can change that.

from dynamicquantities.jl.

Thanks Miles! I did change all instances of us"Constants.pc" to just Constants.pc, and that worked also. I'm using Julia 1.9 — my versioninfo() is shown below.

Julia Version 1.9.3
Commit bed2cd540a1 (2023-08-24 14:43 UTC)
Build Info:
  Official https://julialang.org/ release
Platform Info:
  OS: macOS (arm64-apple-darwin22.4.0)
  CPU: 8 × Apple M1
  WORD_SIZE: 64
  LIBM: libopenlibm
  LLVM: libLLVM-14.0.6 (ORCJIT, apple-m1)
  Threads: 1 on 4 virtual cores

from dynamicquantities.jl.

Awesome. Okay I think we should go with that, what do you think? Then for display, I think @gaurav-arya has a good strategy proposed in #48

Basically, one can display units with as_u (name pending) e.g.,

u"Constants.pc" / 0.05 |> as_u(us"Constants.kpc)

which would display 0.02 kpc, even though the calculation happens with the faster Dimensions.

from dynamicquantities.jl.

Works for me, and I like the unit conversion feature and syntax. The |> is convenient. I also like the Unitful.uconvert syntax, I see some benefit to having multiple different methods for as_u so there are different options for converting one quantity's units to another: as_u(u"km", 100u"m") or 100u"m" |> as_u(u"km").

So all of this is good for display and for my purposes, but could this issue pop up again? If I understand correctly, symbolic units can't be used in any Julia package, because they're created on-the-fly. With native code cacheing in Julia v1.9 and later, I wonder how much slower the package would be if all of the symbolic units are created at once? If no one has done that experiment yet, and if there's interest in the future, I'd be interested in trying that out.

from dynamicquantities.jl.

Okay now this issue is fixed for real – please try it out! You can do, e.g.,

const my_unit = us"ohm"

just fine, and precompilation should be good

from dynamicquantities.jl.