David Turner writes:

On 11 May 2017 at 19:40, Ben Gamari wrote:

...

Ccing Luke Maurer under the assumption that he will appreciate seeing the fruits of his labor.

David Turner writes:

...

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.

Ooo, that's more like it.

Could you run again using the following to get Criterion's estimate of the allocations-per-call?

json-validator-exe --regress allocated:iters +RTS -T benchmarking json-validator/Automaton/testEvent

Here it is, GHC 8.0.2 benchmarking json-validator/Automaton/testEvent time 34.81 μs (33.48 μs .. 36.10 μs) 0.991 R² (0.988 R² .. 0.994 R²) mean 34.04 μs (33.28 μs .. 34.99 μs) std dev 2.828 μs (2.423 μs .. 3.247 μs) allocated: 1.000 R² (1.000 R² .. 1.000 R²) iters 65924.651 (65895.364 .. 65951.510) y -4175.284 (-46736.295 .. 39814.235) variance introduced by outliers: 78% (severely inflated) GHC 8.2 benchmarking json-validator/Automaton/testEvent time 9.021 μs (8.923 μs .. 9.162 μs) 0.998 R² (0.994 R² .. 1.000 R²) mean 8.970 μs (8.905 μs .. 9.232 μs) std dev 341.4 ns (94.90 ns .. 711.7 ns) allocated: 0.973 R² (0.956 R² .. 0.984 R²) iters 343.033 (332.692 .. 354.606) y -7326.339 (-57269.638 .. 47222.231) variance introduced by outliers: 47% (moderately inflated) Cheers, - Ben