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Package roles and alternatives

SnoopCompileCore

SnoopCompileCore is a tiny package with no dependencies; it's used for collecting data, and it has been designed in such a way that it cannot cause any invalidations of its own. Collecting data on invalidations and inference with SnoopCompileCore is the only way you can be sure you are observing the "native state" of your code.

SnoopCompile

SnoopCompile is a much larger package that performs analysis on the data collected by SnoopCompileCore; loading SnoopCompile can (and does) trigger invalidations. Consequently, you're urged to always collect data with just SnoopCompileCore loaded, and wait to load SnoopCompile until after you've finished collecting the data.

Cthulhu

Cthulhu is a companion package that gives deep insights into the origin of invalidations or inference failures.

AbstractTrees

AbstractTrees is the one package in this list that can be both a "workhorse" and a developer tool. SnoopCompile uses it mostly for pretty-printing.

JET

JET is a powerful developer tool that in some ways is an alternative to SnoopCompile. While the two have different goals, the packages have some overlap in what they can tell you about your code. However, their mechanisms of action are fundamentally different:

  • JET is a "static analyzer," which means that it analyzes the code itself. JET can tell you about inference failures (runtime dispatch) much like SnoopCompile, with a major advantage: SnoopCompileCore omits information about any callees that are already compiled, but JET's @report_opt provides exhaustive information about the entire inferable callgraph (i.e., the part of the callgraph that inference can predict from the initial call) regardless of whether it has been previously compiled. With JET, you don't have to remember to run each analysis in a fresh session.

  • SnoopCompileCore collects data by watching normal inference at work. On code that hasn't been compiled previously, this can yield results similar to JET's, with a different major advantage: JET can't "see through" runtime dispatch, but SnoopCompileCore can. With SnoopCompile, you can immediately get a wholistic view of your entire callgraph.

Combining JET and SnoopCompile can provide insights that are difficult to obtain with either package in isolation. See the Tutorial on JET integration.