Show --compile with --help (and support better)

[PallHaraldsson]

A. Since --compile=min works (even as of 1.6, and I guess all versions since 1.0) and can be MUCH faster (for loading code), show it!

Is there a reason it's undocumented? Are some of of the options dangerous, or other reason undocumented? I believe they are "yes", "no", and "min", and if I recall for pre-1.0 "min" could crash?

B. As with Jeff's new selective lowered optimization trick, being able to get the above option that way would be nice. I'm not sure if that's an easy change, while even I could make a PR for A. unless it's not wanted.

C. Letting the user choose for the new opt option and/or possible B. would be nice, as e.g. @lowopt using Module and even better if possible more granularity, i.e. for functions (loops?).

[JeffBezanson]

It's not dangerous and should always work (if it crashes or errors unexpectedly, file an issue). But, it can make code run hundreds of times slower, so it's not a practical option in general. It is listed under --help-hidden, but the text there does need more explanation.

We could indeed apply --compile=min at the module level; we should add that. It really is very slow, but still worth experimenting I guess.

[PallHaraldsson]

I did and Julia's defaults can be 3.7x slower: JuliaInterop/RCall.jl#383 (comment)

And in that case the line (the last one, i.e. not using) which called the wrapper, was even faster on first use, and afterwards as fast as on defaults. This would be good in such situations, or for JLLs.

[derekmahar]

By the way, --compile=min is missing from the Julia 1.4.1 man page.

[blegat]

@derekmahar The option not displayed with --help but it is with --help-hidden:

$ julia --help-hidden
julia [switches] -- [programfile] [args...]
 --compile={yes|no|all|min}Enable or disable JIT compiler, or request exhaustive compilation
 --output-o name           Generate an object file (including system image data)
 --output-ji name          Generate a system image data file (.ji)
 --output-unopt-bc name    Generate unoptimized LLVM bitcode (.bc)
 --output-jit-bc name      Dump all IR generated by the frontend (not including system image)
 --output-bc name          Generate LLVM bitcode (.bc)
 --output-asm name         Generate an assembly file (.s)
 --output-incremental=no   Generate an incremental output file (rather than complete)
 --trace-compile={stdout,stderr}
                           Print precompile statements for methods compiled during execution.

[derekmahar]

@blegat, yes, but --help and --help-hidden are not the same as the Julia man page.

[PallHaraldsson]

Actually "--help" is in the manual both for current 1.5 and 1.4, but the search feature isn't too good:

https://docs.julialang.org/en/v1/manual/getting-started/

"--help-hidden" isn't there, yes (while can be found from "--help" itself), but in 1.7 manual neither is for that page (I assume just moved and maybe "--help-hidden" is in).

[It's easier to search in a PDF file, and I tracked down an old one for the manual.]

It would be good that the manual is searchable for e.g. "--sysimage" and "--compile-min" too.

[derekmahar]

@blegat @PallHaraldsson

I think you may have misunderstood my point or I was not clear. The option --compile=min is absent from the Julia man page, not the help page.

ubuntu@development1:~$ man julia
.
.
.
       --compile={yes|no|all}
              Enable or disable compiler, or request exhaustive compilation
.
.
.

Note that this differs from the specification of option --compile= present in julia --help-hidden.

[PallHaraldsson]

Still, for

$ man julia

I already have:

  --compile={yes|no|all|min}
         Enable or disable compiler, or request exhaustive or minimal compilation

I think it's looking at:
/home/pharaldsson_sym/julia-1.6-a0a68a54d6/share/man/man1/julia.1

For some reason the man page still ends with: 2013-12-10

"min" is not in:
/home/pharaldsson_sym/julia-1.5-012b270df6-old/share/man/man1/julia.1

It could be backported to Julia 1.5.4 but I'm not sure really needed, with Julia 1.6 release around the corner.

[I've installed and uninstalled a lot of Julia versions over time. I have 22 Julia installations, from 0.4 to 1.7, plus have used snap install that I do not advice (last I checked it wasn't updated). At first I though man looks only in .deb installs. "It is strongly recommended that the official generic binaries from the downloads page be used to install Julia on Linux and FreeBSD."]

[derekmahar]

Yes, because I reported and fixed #36585. In my earlier comment, I should have written, "The option --compile=min was absent from the Julia man page, not the help page."