Array languages

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General discussion about APL-like array languages. See #array:matrix.org for other rooms13 Servers

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9 Jan 2022
@dzaima:matrix.orgdzaima oh and primes/factorization 18:57:28

×´ appears twice in primes.bqn, once for finding the size of the sieve's wheel, and once for the totient function.

@_discord_595317473247756288:t2bot.ioAlex Shroyer In probabilities for sure. Also markov chain monte carlo method and some signal processing functions.
Usually multiplying floats in the range from 0 to 1.

There's a reduction with modular multiplication for computing a modular exponent in Miller-Rabin, but it's still logarithmic in length.


And that's not the best method either, just easier to write.

@_discord_768182477449592832:t2bot.ioSouth ohhhhh markov chains, now that would be fun in J 19:13:20
@_discord_595317473247756288:t2bot.ioAlex Shroyer unfortunately I've only done it in python so far 19:13:46
@_discord_595317473247756288:t2bot.ioAlex Shroyer but I've used np.prod multiple times (analogous to */) 19:14:11

Some Markov-related J code here. Only */ is an outer product, not a reduction.

@_discord_272556648134868992:t2bot.ioInternet Janitor I'm specifically interested in the reduction case 20:57:28
10 Jan 2022
@_discord_595317473247756288:t2bot.ioAlex Shroyer Internet Janitor I looked at my github repos, and found several cases of using np.prod:

1. vectorizing an image np.prod((rows, cols))
2. concatenating column vectors of an n by n image np.zeros((n*n, np.prod((rows,cols))))
3. inner loop of Viterbi algorithm, np.prod((a,b,c)) in place of a*b*c
4. calculating probabilities in naive bayes (spam email classifier)
5. naive bayes again, this time in inner loop of iterated conditional mode (ICM) using markov random fields
6. another np.prod((rows, cols)) to vectorize an image
7. used in this code challenge problem (discussed on ArrayCast) https://www.codewars.com/kata/5a905c2157c562994900009d
@_discord_595317473247756288:t2bot.ioAlex Shroyer The only cases which really call for */ are the naive bayes and the "product array" problem. 14:22:38
@_discord_595317473247756288:t2bot.ioAlex Shroyer So 3/7. 14:22:47
@_discord_272556648134868992:t2bot.ioInternet Janitor Alex Shroyer thank you; that's very helpful 15:29:36
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