#13360: Add a flag to enable inferring HasCallStack constraints -------------------------------------+------------------------------------- Reporter: gridaphobe | Owner: (none) Type: feature request | Status: new Priority: normal | Milestone: 8.4.1 Component: Compiler | Version: 8.0.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by saurabhnanda): Here are some benchmarks for postgresql-simple, a project which is doing significant real-world IO (which is where most errors occur, in my experience): **No Callstack -- Benchmarking a query with/without error** {{{ benchmarking complicatedQuery/without error time 172.3 μs (169.0 μs .. 175.2 μs) 0.985 R² (0.971 R² .. 0.993 R²) mean 224.5 μs (203.3 μs .. 271.1 μs) std dev 110.9 μs (58.97 μs .. 200.8 μs) variance introduced by outliers: 99% (severely inflated) benchmarking complicatedQuery/with error time 171.4 μs (169.6 μs .. 173.5 μs) 0.996 R² (0.992 R² .. 0.999 R²) mean 174.4 μs (171.3 μs .. 179.8 μs) std dev 14.00 μs (8.934 μs .. 19.24 μs) variance introduced by outliers: 72% (severely inflated) }}} **HasCallStack -- Benchmarking same query but with [https://github.com/vacationlabs/postgresql- simple/commit/774d3eaa259c217ada3918e5c29f3dab792af38c: HasCallStack applied on almost every function of the library]** {{{ benchmarking complicatedQuery/without error time 177.9 μs (176.3 μs .. 180.6 μs) 0.996 R² (0.992 R² .. 0.998 R²) mean 186.8 μs (182.6 μs .. 192.6 μs) std dev 17.42 μs (13.92 μs .. 21.59 μs) variance introduced by outliers: 78% (severely inflated) benchmarking complicatedQuery/with error time 171.4 μs (168.7 μs .. 175.6 μs) 0.991 R² (0.981 R² .. 0.997 R²) mean 175.3 μs (171.4 μs .. 182.1 μs) std dev 17.27 μs (11.45 μs .. 25.30 μs) variance introduced by outliers: 80% (severely inflated) }}} The difference in perf is coming across as almost noise. **Is this an acceptable benchmark for measuring real-world impact of enabling HasCallstack for IO-centric functions? Does this strengthen the case for implementing this flag?** -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/13360#comment:20 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler