Ccing Luke Maurer under the assumption that he will appreciate seeing
the fruits of his labor.
David Turner
Dear Café,
(snip)
There's a copy of the relevant code for option 4 at https://github.com/DaveCTurner/json-validator. I've hacked around with it a bit since producing the numbers above, so it's now apparently a bit slower than Aeson but allocates less too (~65kB).
Could anyone help, e.g. by pointing me at the bit in the Core that is allocating within the main loop?
While turning this over in my head I realized that this is the sort of program which may be helped significantly by GHC 8.2's improved join point handling. Indeed the timings seem to support this hypothesis: GHC 8.0.2 benchmarking json-validator/Automaton/testEvent time 22.84 μs (22.76 μs .. 22.94 μs) 1.000 R² (1.000 R² .. 1.000 R²) mean 22.84 μs (22.76 μs .. 22.94 μs) std dev 297.4 ns (221.8 ns .. 378.8 ns) Alloc rate 4,015,256,078,038 bytes per MUT second GHC 8.2 benchmarking json-validator/Automaton/testEvent time 9.221 μs (9.141 μs .. 9.318 μs) 0.998 R² (0.996 R² .. 1.000 R²) mean 9.163 μs (9.084 μs .. 9.356 μs) std dev 399.8 ns (193.0 ns .. 745.4 ns) variance introduced by outliers: 54% (severely inflated) Alloc rate 123,141,635 bytes per MUT second Wow! I suspect your allocations have now vanished. I didn't verify that the improvement really was due to more join points, but it seems quite likely. Well done Luke! Cheers, - Ben