20190614, 20:38  #45 
Jun 2019
3_{10} Posts 
Bernard Fabrot: Solves LCS35. Good job!

20190614, 21:32  #46  
Undefined
"The unspeakable one"
Jun 2006
My evil lair
2·23·137 Posts 
Quote:
The result won't come any faster, but you can detect an error sooner and backtrack with the loss of only one iteration. 

20190617, 13:34  #47  
May 2019
13 Posts 
Quote:
If wonder if the best approach (if the goal is to solve it as fast as possible) is not to run one computation without the check (so working with 2048 bit numbers) and then having the second computation running with the check (say performing a 2096 bit multiplication). I realized that in my case a slowdown on my main computation of 2% and I wouldn't have been the first to find the solution! And I did try: using a 50 bit prime for the check would slow my main computation of more than 5%. So I wouldn't have win had my main computation been running the check. Now of course if the second computation runs with the check and an error is detected near the beginning, you don't lose much time to backtrack from the last correct intermediate result. But if the second computation detects an error towards the end, because the second computation is x% slower, it means the main computation needs to backtrack by x%, which can be quite some time. 

20190617, 14:13  #48 
Undefined
"The unspeakable one"
Jun 2006
My evil lair
2·23·137 Posts 
I think just running two instances of the same capability in parallel is very easy. So they can run in lock step with each other. Instant verification after each iteration with a comparison circuit that can signal a backtrack if there is a difference.

20190622, 07:33  #49 
Jun 2019
3 Posts 
Solution
!!! Congratulations CSAIL !!!
Last fiddled with by Sergio Siller on 20190622 at 07:41 
20190624, 02:38  #50 
"Kevin W. Hake"
May 2019
5 Posts 
The second computation can be multithreaded; every time your main, fast computation records its progress, a thread can be spun up to check it. So let's say your main thread records progress every 5 minutes. Even if the secondary check ran 50% slower, 2 cores would complete 2 of those blocks in 10 minutes (or 1 block in 5 minutes, the same rate as the main thread); they would never fall far behind.
Last fiddled with by kevinhake on 20190624 at 02:41 
20190624, 07:05  #51 
Jun 2019
3 Posts 

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