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From: Vir Campestris <vir.campestris@invalid.invalid>
Newsgroups: comp.lang.c++
Subject: Re: Sieve of Erastosthenes optimized to the max
Date: Thu, 16 May 2024 17:28:55 +0100
Organization: A noiseless patient Spider
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I've been playing with this. Has it really been this long? I ought to 
have more time than this...

I put together some code, and have been playing with it far too much.

Bonita, I don't know whether to curse you or kiss you. (Though in fact I 
suspect you may be a little young for me. Possibly too young for my kids...)

I haven't written any code just for fun in years. Maybe decades!

I missed Tim's Mod 30 trick, and that might well help. But I think I'm 
bored with this. It would save a lot of memory, but the extra 
computation might make it slower. Maybe I'll try one day ;)

My code isn't as fast as Bonita's code. Even allowing that I didn't put 
any threads in there.

But...

When I compared the output there were differences. Specifically your 
program claimed that these numbers

66049,67591,69133,69647,71189,72217,72731,75301,78899,79927,80441,81469,85067,86609,89179,
89693,90721,92263,94319,95861,97403,98431,99973,102029,103057,105113,107683,108197,110767,
111281,112823,113851,115393,117449,118477,118991,120019,123103,125159,126187,128243,129271,
130813,133897,134411,139037,140579,143149,144691,146233,146747,148289,150859,152401,153943,
154457,155999,157541,158569,159083,162167,164737,165251,166279,167821,169363,169877,172961,
173989,175531,177587,180157,182213,184783,186839,188381,189923,190951,193007,194549,195577,
197633,198661,202259,204829,207913,208427,210997,211511,212539,213053,215623,219221,220249,
220763,221791,225389,226417,226931,227959,233099,234127,236183,238753,240809,241837,243379,
244921,248519,249547,251089,252631,254687,256229,259313,260341,261883,262397,264967,265481,
267023,269593,270107,272677,273191,274733,279359,280387,280901,281929,283471,285013,287069,
288611,290153,295807,296321,298891,300947,303517,305059,306601,308657,311741,312769,314311,
315853

are all prime. They aren't. The first one is 257 squared, and the others 
all have factors too.

I'd also suggest that you comment demonstration code. It's intended to 
show off fancy techniques, and they aren't obvious without explanation.

I learned that lesson when I was a student, when I couldn't understand 
something I'd written myself!

Andy