andrewthad

{-# language BangPatterns #-}

main :: IO ()
main = print (createMap myList)

myList :: [String]
myList = ["foo","bar","foo","bar"]

-- updateMap :: Map String Int -> String -> Map String Int
-- updateMap v k = Map.updateWith (+1) k m

andrewthad

Strictness in Kinds

Let's tweak GHC's RuntimeRep stuff to try adding information about strictness. This information could be helpful for avoiding evaluating thunks that are guaranteed to already be evaluated. Presently, RuntimeRep is defined as:

data RuntimeRep

= LiftedRep

andrewthad

This is an idea for how to case on a byte sequence without any special support from the compiler. The basic idea is explored in https://github.com/layer-3-communications/fortios-syslog, but there code generation is used rather than TemplateHaskell. The idea is that, at compile time, generating a perfect hash function for all strings of the same length is a good way to pattern match on a sequence of bytes. Roughly, we have:

foo :: Bytes -> Bar
foo b = case B.length b of
  3 -> case hash3 b of

Car | b == "car" -> ...

andrewthad

	Sat May 23 19:57 2020 Time and Allocation Profiling Report  (Final)

	   ghc +RTS -p -RTS -B/home/amartin/ghc-boxedrep-prof/lib/ghc-8.11.0.20200518 ./testsuite/tests/perf/compiler/T5030.hs

	total time  =        0.56 secs   (558 ticks @ 1000 us, 1 processor)
	total alloc = 711,938,744 bytes  (excludes profiling overheads)

COST CENTRE             MODULE                  SRC                                                 %time %alloc

simplCast-simplCoercion GHC.Core.Opt.Simplify   compiler/GHC/Core/Opt/Simplify.hs:1293:57-77         28.5   30.5

andrewthad

'/home/amartin/ghc-boxedrep-ticky/lib/ghc-8.11.0.20200515/bin/ghc' '-B/home/amartin/ghc-boxedrep-ticky/lib/ghc-8.11.0.20200515' '-O2' './testsuite/tests/perf/compiler/T5030.hs' +RTS '-rboxedrep.ticky' 

STACK USAGE:

ENTERS: 124184476  of which 124184476 (100.0%) direct to the entry code
		  [the rest indirected via Node's info ptr]
   19582791 ( 15.8%) thunks
   21067039 ( 17.0%) data values
          0 (  0.0%) normal indirections
          0 (  0.0%) permanent indirections

andrewthad

{-# LANGUAGE ImplicitParams #-}

example1 :: (?a :: Int) => [Int]
example1 = let ?a = 4 in [foo,bar + bar,(?a + 3) + (?a + 3)]
  where
  foo = bar + bar
  bar = ?a + 3

example2 :: (?a :: Int) => [Int]
example2 = let ?a = 4 in [foo,bar + bar,(?a + 3) + (?a + 3)]

andrewthad

Discerning the Zookeeper Protocol

To write a zookeeper client, it is neccessary to understand the protocol used to communicate with it. Unfortunately, this protocol is not documented. In this example, we use tcpflow to dump both the read and write channel of the TCP connection that zkCli.sh uses to connect with the zookeeper server.

Requests

andrewthad

-- This is a riddle about people's ages that I made up. Below, we solve it
-- using the monadic interface to lists. Here it is:
--
-- * Jordan is either 13 years old or 16 years old
-- * Shen is between 3 and 5 years older than Jordan (inclusive bounds)
-- * Claudia is between 6 and 9 years younger than Jordan's age plus Shen's age.
-- * I am as old as the three aforementioned people combined.
--
-- Given the provided information, I could have many possible ages. The monad
-- instance for list models this kind of nondeterminism well. Run the example

andrewthad

checkFamInstConsistency [Prelude]
Tc2 (src)
Tc3
tcExtendKindEnvList []
tcExtendKindEnvList []
tcDeriving False
tcDeriving 1 []
rnd
Adding instances:
Tc3b

andrewthad

benchmarked encode/base64-bytestring/25
time                 161.7 ns   (152.6 ns .. 168.1 ns)
                     0.980 R²   (0.944 R² .. 0.998 R²)
mean                 178.6 ns   (169.1 ns .. 216.5 ns)
std dev              55.41 ns   (14.38 ns .. 113.1 ns)
variance introduced by outliers: 95% (severely inflated)

benchmarked encode/base64-bytestring/100
time                 232.1 ns   (228.7 ns .. 234.8 ns)
                     0.999 R²   (0.998 R² .. 0.999 R²)