Making packages work faster with more extensive precompilation



Build Status

SnoopCompile "snoops" on the Julia compiler, getting it to log the functions and argument-types it's compiling. By parsing the log file, you can learn which functions are being precompiled, and even how long each one takes to compile. You can use the package to generate "precompile lists" that reduce the amount of time needed for JIT compilation in packages.

SnoopCompile is not recommended for Julia beginners, and even experienced users may need several iterations to generate precompile scripts that work.


The easiest way to describe SnoopCompile is to show a snoop script, in this case for the Images package:

using SnoopCompile

### Log the compiles
# This only needs to be run once (to generate "/tmp/images_compiles.csv")

SnoopCompile.@snoop "/tmp/images_compiles.csv" begin
    include(Pkg.dir("Images", "test","runtests.jl"))

### Parse the compiles and generate precompilation scripts
# This can be run repeatedly to tweak the scripts

data = SnoopCompile.read("/tmp/images_compiles.csv")

pc = SnoopCompile.parcel(reverse!(data[2]))
SnoopCompile.write("/tmp/precompile", pc)

After the conclusion of this script, the "/tmp/precompile" folder will contain a number of *.jl files, organized by package. These files could be added to a package like this:

module SomeModule

# All the usual commands that define the module go here

# ... followed by:


end # module SomeModule

There's a more complete example illustrating potential options in the examples/ directory.


Currently, precompilation does not cache functions from other modules; as a consequence, your speedup in execution time might be smaller than you'd like. In such cases, one strategy is to generate a script for your base/userimg.jl file and build the packages (with precompiles) into julia itself. Simply append/replace the last two lines of the above script with

# Use these two lines if you want to add to your userimg.jl
pc = SnoopCompile.format_userimg(reverse!(data[2]))
SnoopCompile.write("/tmp/userimg_Images.jl", pc)

Users are warned that there are substantial negatives associated with relying on a userimg.jl script:

  • Your julia build times become very long
  • Pkg.update() will have no effect on packages that you've built into julia until you next recompile julia itself. Consequently, you may not get the benefit of enhancements or bug fixes.
  • For a package that you sometimes develop, this strategy is very inefficient, because testing a change means rebuilding Julia as well as your package.

First Commit


Last Touched

5 days ago


24 commits


Used By: