mersenneforum.org serious bug in aliquot.ub
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2009-03-05, 17:48   #1
Andi47

Oct 2004
Austria

2×17×73 Posts
serious bug in aliquot.ub

Quote:
 Originally Posted by schickel Andi47, unfortunately it looks like you got bit by the ubasic bug again. The factorization of line 1581*) was recorded wrong, invalidating the succeeding lines. I re-did a couple of lines; it looks like the ubasic program has serious issues when the sequence is up that high.
*) I think this refers to sequence 181410

I will try if the bug is reproducible this weekend and additionally try to run a few lines manually.

A second case of the bug, which seems to be reproducible (at least I got the same set of nonsense factors with the same "variable area full" crash three times before I gave up) is in sequence 168804, starting with line 694 and trying to calculate line 695:

Quote:
 Originally Posted by Andi47 Sequence 168804 Code:  690 . 50103592439273417765455674112419058395015246692752819021428935169183229439339883436403456844 = 2^2 * 3^3 * 17 * 30824336467 * 491795222813 * 13584298984407563519 * 114083094084012348329 * 1161608078703468047677953049 691 . 87435680928179628070197301637552945425210263223149452662176810277141381087583138264306943156 = 2^2 * 3^3 * 17 * 2137 * 369397632948149979033671706760102207657693 * 60327786293702353483825607354175652491638731 692 . 152696151450202438359481984205275535262156186630649022909831360423191454696892957165345341004 = 2^2 * 3^2 * 273607447 * 1154753038283154251 * 15241503701075456647 * 880806979345377075224336852056163707065321521 693 . 233285788348523582351079428302479202091390805818226802622805708025054796780158201758336268212 = 2^2 * 3^2 * 631 * 673 * 622807062847608389 * 24501226740208998749664531058825028416950572326161336857217774877031 694 . 358220989634069824870234071770131383640271305023140756549961418271453639806064943450895838028 = 2^2 * 3^2 * 7406233 * 72520355581 * 113380251588132676571 * 854327445452909216994437 * 191262337054620722724732940313 I give up. This sequence hits too many bugs (now it's a reproducible "variable error full" in iteration 695, producing funny factors), and I don't have time to run it manually.

Last fiddled with by Andi47 on 2009-03-05 at 17:49 Reason: typo

 2009-03-07, 12:10 #2 Andi47     Oct 2004 Austria 1001101100102 Posts @Smh: As the bug sometimes (but not always) comes with an "out of variable space" crash, could it possibly help to rise word 100 to something like "word 130" in line 220, or to rise the size of the matrices in line 230?
2009-03-08, 09:48   #3
smh

"Sander"
Oct 2002
52.345322,5.52471

4A516 Posts

Quote:
 Originally Posted by Andi47 @Smh: As the bug sometimes (but not always) comes with an "out of variable space" crash, could it possibly help to rise word 100 to something like "word 130" in line 220, or to rise the size of the matrices in line 230?
No idea. I'm by no means an UBasic expert. I'll guess the only way to find out is try?

2009-03-08, 10:18   #4
schickel

"Frank <^>"
Dec 2004
CDP Janesville

2×1,061 Posts

Quote:
 Originally Posted by Andi47 @Smh: As the bug sometimes (but not always) comes with an "out of variable space" crash, could it possibly help to rise word 100 to something like "word 130" in line 220, or to rise the size of the matrices in line 230?
Quote:
 Originally Posted by smh No idea. I'm by no means an UBasic expert. I'll guess the only way to find out is try?
Without being able to look at the ubasic source, I'd bet not. The "word" size is the bit-size of the variables. I'm assuming that the "out of variable space" means that the total amount of space available for variables is exhausted, not that any one variable has grown too big. (In fact, a test would be to set "word" low and see what happens if a variable overflows.....does it cause an error, or does it wrap around?)

My impression has been that one type of crash occurs when a composite (especially a large one) factors into "too many" primes. If space for array variables is only allocated as the array is filled, that would explain that type of crash. The limited variable space runs out when "too many" factors are found.

With "word" at 100, the integer precision is set at ~481 digits. A test you might try is setting "word" lower and see if that causes trouble with the internal ECM code. "word 50" should be adequate for current work, that's 240 integer digits....not sure where that puts the floating point precision, though.

Edit: Just tested....if a variable overflows, an "overflow in ...." error is reported. So you might try setting "word" lower and see what happens.

Last fiddled with by schickel on 2009-03-08 at 10:28 Reason: Added "edit"

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