> I think you understand perfectly.
i'm coming around
> You said the keys are 128-bit (16 byte) values. You can store one key
> directly in a byte string of length 16.
yup
> So instead of using a vector of pointers to individual byte strings,
> you would allocate a single byte string of length
> {buckets x chain length x 16}
> and index it directly as if it were a 3-dimensional array [using
> offset calculations as you would in C].
i'm going to actually run my code later (probably in the morning). and then
grab some stats from the hash. take a look at the stats. give me some thoughts
on the above implementation after looking at the stats.
> Can you explain why the bignums are important. For a simple task like
> filtering a file, they would seem to be both a waste of memory and a
> performance drain wrt storing the key values as byte strings.
ok, true story. about 10 years ago i'm a student taking an intro to ai class we
have been assigned the 3x3 tile puzzle and 2 algorithms, ida* and a*. also, try
it on a 4x4. so i whip these out and am appalled by how slow the fn things are
but intrigued by what they can do and i'm just a puzzle kind of guy. btw, the
4x4 wasn't solvable by my stuff at the time. so i head to the chief's office
with my little bit of code. tell him it's way to slow. what do you think? he
takes 5 seconds to peruse the item and says "you're probably making too much
memory". side note, later i graded this class for that prof and the same
project. not a single student, including the ms and phd types, did anything
better than a vector of vectors of ints. so back to me, i'm thinking, how do i
cram 4 bits together so that there is absolutely no wasted space. i start
digging through the documentation and i find the bitwise stuff. i see
arithmetic shift and having no idea whether it will work or not i type into the
interface (arithmetic-shift 1 1000000). if we blow up, well we blow up big but
we didn't. i flipped everything in my project to bignum at that point. the
bignum stuff is massively faster than vector of vectors of ints and faster than
just a single vector of ints. lots of bignum is easy to implement, like the
hash. making a child state, not so much. i'm not married to bignums despite all
this.
> I've been programming for over 30 years, professionally for 23.
i was a programmer. dot com bought us as a brick and mortar back in '99 and the
whole shebang blew up 2 years later. idiots. anyway, been a stay at home dad
for the most part since then.
> have an MS in Computer Science
me too. that's the other piece of the most part from up above.
> (current-memory-use)
yup, tried that a while back didn't like what i saw. check this out:
> (current-memory-use)
581753864
> (current-memory-use)
586242568
> (current-memory-use)
591181736
> (current-memory-use)
595527064
does that work for you?
--
You received this message because you are subscribed to the Google Groups
"Racket Users" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to racket-users+unsubscr...@googlegroups.com.
For more options, visit https://groups.google.com/d/optout.
