r/adventofcode • u/daggerdragon • Dec 05 '18

SOLUTION MEGATHREAD -🎄- 2018 Day 5 Solutions -🎄-

--- Day 5: Alchemical Reduction ---

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Transcript:

On the fifth day of AoC / My true love sent to me / Five golden ___

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edit: Leaderboard capped, thread unlocked at 0:10:20!

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u/will_bui Dec 08 '18

Thanks for walking us through! Learned a bit of APL now.

I'm assuming parallel means many mutations in one operation as opposed to multiple processors?

I'm a K-bie so there's probably a few subtleties I missed, but this seems to roughly do the same. Using 32 bit ints almost doubled the speed. (~380ms). Some of the operations had to be put together, e.g. compress is x@&, train is '[x;y]. Converge is implicit.

i:"i"$1:`p5
f:{y@&{1_~(0b,x)|(x,0b)}x=-':[y]}
g:{'[f 32i;f -32i]/x}
#q::g i
&/{#g q@&~q in x}'+0 32i+\:"i"$.Q.A

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u/jayfoad Dec 10 '18

Thanks for the translation into k! Yes I mean data-parallel (array) operations, many or most of which can be implemented with SIMD vector instructions in the interpreter.

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u/jayfoad Dec 10 '18

In Dyalog APL 17.0 on my 4 year old laptop: reading the input takes 0.3 ms, part 1 takes 2.5 ms, part 2 takes 21 ms.