4 ms·

The joke is completely lost on me. I don't even mean the person who did this — why not, after all. 1198 upvotes ATM is what confuses me. Lookup tables for comp

by krick 3y ago

The joke is completely lost on me. I don't even mean the person who did this — why not, after all. 1198 upvotes ATM is what confuses me. Lookup tables for computable values are not novel, nor are they a joke. This actually is a solutions for the time/memory tradeoff, as author well knows. The problem at hand is absurd, but quite primitive, so there was absolutely no doubt this can be done. No real measurements were performed, apart from the observations that it took about 10 seconds to chew through 40GB program on his computer. So what did we learn? That exe files cannot be more than 4GB? That a program with 2^32 ifs is about 300 GB? Why 1198 people found this interesting? Maybe I'm spoiled, but unlike "Hexing the technical interview" or some SIGBOVIK stuff, this doesn't seem crazy, just pointless.

corysama 3y ago
The joke is that he actually did it. People have been joking about it for decades. But, the crazy bastard did it for real. It’s so extreme that no compiler could handle it. Not even any known assembler. So, he had to generate his own machine code binary to make it work. But, it works! Nutz!
segfaltnh 3y ago
Sometimes people do things to be funny.
peeters 3y ago
> Lookup tables for computable values are not novel, nor are they a joke It's been ages since I've done anything low-level, but I don't think 4 billion if-statements are compiled to a "lookup table" when optimizations are turned off. Each and every if statement would be evaluated in order to determine if it matches the input. This seems to be supported by OP's program outputting in much less time for small numbers than for large numbers--since the small numbers appear earlier in the code. A 4 billion case switch statement on the other hand, I would expect to compile to some kind of lookup table. Though when the data type is an unsigned int even then I'm not sure what the compiled code would look like without optimization.
- MBCook 3y ago
  Would a compiler be smart enough to generate a big table for this? I wonder if it’s just so big the optimization pass would give up, or perhaps makes tons of tables of 256 entries each.
  - detuur 3y ago
    Optimization was explicitly disabled by compiler flag for this experiment
Affric 3y ago
My understanding was that it was a parody of these blog posts satirising the pointlessness of pushback against conventional wisdom. Rather dry.

by krick 3y ago

corysama 3y ago

The joke is that he actually did it. People have been joking about it for decades. But, the crazy bastard did it for real. It’s so extreme that no compiler could handle it. Not even any known assembler. So, he had to generate his own machine code binary to make it work. But, it works! Nutz!

segfaltnh 3y ago

Sometimes people do things to be funny.

peeters 3y ago

> Lookup tables for computable values are not novel, nor are they a joke It's been ages since I've done anything low-level, but I don't think 4 billion if-statements are compiled to a "lookup table" when optimizations are turned off. Each and every if statement would be evaluated in order to determine if it matches the input. This seems to be supported by OP's program outputting in much less time for small numbers than for large numbers--since the small numbers appear earlier in the code. A 4 billion case switch statement on the other hand, I would expect to compile to some kind of lookup table. Though when the data type is an unsigned int even then I'm not sure what the compiled code would look like without optimization.

MBCook 3y ago
Would a compiler be smart enough to generate a big table for this? I wonder if it’s just so big the optimization pass would give up, or perhaps makes tons of tables of 256 entries each.
- detuur 3y ago
  Optimization was explicitly disabled by compiler flag for this experiment

Affric 3y ago

My understanding was that it was a parody of these blog posts satirising the pointlessness of pushback against conventional wisdom. Rather dry.