Posts by Sergei Chernykh

1) Message boards : News : Power outage (Message 851)
Posted 2 days ago by Sergei Chernykh
Post:
The server was down today between 11:04 and 14:20 (CEST) because of a major power outage in Hetzner datacenter. Everything should be up and running again now.
2) Message boards : Number crunching : Is source code available? (Message 848)
Posted 9 days ago by Sergei Chernykh
Post:
So the app_name must include info on 10^20. What app_name is set on the server, Sergei?

app_name is amicable_10_20
3) Message boards : Number crunching : Is source code available? (Message 846)
Posted 9 days ago by Sergei Chernykh
Post:
It says "syntax error" because you have mismatched tags:
 <app_name>amicable</name>
4) Message boards : Number crunching : Is source code available? (Message 842)
Posted 10 days ago by Sergei Chernykh
Post:
Thank you for quick response!!! It'll be help me a lot!

Do you have any issues with running the existing Linux binary on your system? Don't forget to make a pull request if your modifications could be useful for other users.
5) Message boards : Number crunching : Is source code available? (Message 840)
Posted 10 days ago by Sergei Chernykh
Post:
https://github.com/SChernykh/Amicable/tree/boinc-version-128-bit
6) Message boards : Number crunching : Newbie questions about the project (Message 838)
Posted 13 days ago by Sergei Chernykh
Post:
Yes, Feb 2019, and yes, it's still an open question.
7) Message boards : Getting started : Raspberry Pi support? (Message 835)
Posted 14 days ago by Sergei Chernykh
Post:
It works on my Raspberry Pi 3 Model B. I use it to compile 64-bit ARM application. But you'll need to install 64-bit Linux on it to run Amicable Numbers.

P.S. https://sech.me/boinc/Amicable/forum_thread.php?id=37#300
8) Message boards : Number crunching : Newbie questions about the project (Message 832)
Posted 16 days ago by Sergei Chernykh
Post:
When are WUs rich in amicable pairs going to start?

They're already finished. Next time will be in 2019 when the project starts the search up to 1021.
9) Message boards : Number crunching : Newbie questions about the project (Message 830)
Posted 18 days ago by Sergei Chernykh
Post:
what it means to have a factorization between a certain factorization and another, could you define it?

Factorization order is defined as follows: take two factorizations A and B in normalized form (all factors ordered from smallest to largest), compare respective factors one by one until there is a difference. If n-th factor from A is less than n-th factor from B then factorization of A precedes factorization of B. If n-th factor matches, but its power is less than in B (for example, 172 and 173) then again factorization of A precedes factorization of B.

Example: 3^7*5^2*13*311*32189 precedes 3^7*5^2*13*487*1399 because 311 < 487

Also, how can you spot all the numbers with largest prime factor between two certain numbers when you perform the second type of search?

The second part of the search goes through all numbers of the form N*p < 1020 where p is a prime number between numbers in the command line and N goes through all amicable candidates which are < 1020/p. All these candidates are calculated when a work unit starts to execute, it takes a few seconds to do.
10) Message boards : News : GPU version fix (Message 827)
Posted 19 days ago by Sergei Chernykh
Post:
We caught up more than a month ago, it's all new work now.
11) Message boards : Number crunching : Newbie questions about the project (Message 824)
Posted 22 days ago by Sergei Chernykh
Post:
There is no short answer to these questions, it's better to read the article describing the algorithm: https://sech.me/ap/articles.html#a1 - especially part 3, "Reducing search space".
12) Message boards : Number crunching : Newbie questions about the project (Message 822)
Posted 23 days ago by Sergei Chernykh
Post:
/task_size parameter is how many numbers to check in this work unit. It's used to calculate WU progress.
13) Message boards : Random stuff : Project Status Page (Message 819)
Posted 26 days ago by Sergei Chernykh
Post:
I7-5960X is one of the reference CPUs here: https://sech.me/boinc/Amicable/gpu_list.php. Those numbers might be a bit outdated because they were measured for the search up to 264. I'll update them in a few days.
14) Message boards : Number crunching : Newbie questions about the project (Message 816)
Posted 26 days ago by Sergei Chernykh
Post:
All the amicable pairs under 1020. I meant that it's only needed to check ~2.5% of all numbers below 1020 to do that.
15) Message boards : Number crunching : Newbie questions about the project (Message 814)
Posted 26 days ago by Sergei Chernykh
Post:
1) Not through all numbers, only through numbers that can't be proven to not be amicable. ~2.5% of all numbers need to be checked.
2) Distribution of amicable numbers is not uniform and heavily depends on their factorization.
3) Factorization is provided for convenience. It allows to check the numbers quickly.
4) I don't track it, although I save all completed work units and I know how much CPU time each work unit takes on average.
16) Message boards : Random stuff : Project Status Page (Message 809)
Posted 27 days ago by Sergei Chernykh
Post:
Fixed it, thanks for noticing.
17) Message boards : Number crunching : Unable to get more than 20WU (Message 801)
Posted 27 Apr 2018 by Sergei Chernykh
Post:
No, the number of CPU cores that count for this restriction is what you can see in your Computers belonging to page.

P.S. Actually, BOINC client settings can change this number. But "Max # CPUs" setting shouldn't influence it.
18) Message boards : Bug tracker : Not getting GPU workunits (Message 799)
Posted 27 Apr 2018 by Sergei Chernykh
Post:
Check your global BOINC client preferences. You have "Run GPU tasks if user is active" unset.
19) Message boards : Bug tracker : The project send tasks to a video card with only 1G memory (Message 795)
Posted 20 Apr 2018 by Sergei Chernykh
Post:
Decrease kernel size for NVIDIA GPUs in project preferences. Current WUs should work now even on 1 GB cards.
20) Message boards : Number crunching : GPU version requirements for the search up to 10^20 (Message 793)
Posted 19 Apr 2018 by Sergei Chernykh
Post:
Now that WU's allocate less than 900MB, is it possible to relax the GPU memory requirement to 1GB ?

I'll try to do it today and then watch if I get any new WU errors on the project.
21) Message boards : Bug tracker : Not getting CPU units (Message 789)
Posted 13 Apr 2018 by Sergei Chernykh
Post:
I didn't change anything on the project side recently, so it's something with your settings. Check here: https://sech.me/boinc/Amicable/prefs.php?subset=project
22) Message boards : Number crunching : Unable to get more than 20WU (Message 787)
Posted 3 Apr 2018 by Sergei Chernykh
Post:
The project has never been down for more than a few minutes so far, it's running on a dedicated server in a data center. Is it a real issue for you? Do you often get disconnected for many hours?
23) Message boards : Number crunching : Unable to get more than 20WU (Message 785)
Posted 3 Apr 2018 by Sergei Chernykh
Post:
The limitation is 20 WU per single GPU and 2 WU per single CPU core.
24) Message boards : News : GPU version fix (Message 782)
Posted 27 Mar 2018 by Sergei Chernykh
Post:
Good news: I was able to narrow down the invalid work units range to only last 9 days after further analysis of this bug.
25) Message boards : News : GPU version fix (Message 781)
Posted 27 Mar 2018 by Sergei Chernykh
Post:
Is this bug the reason for the semi-random work unit runtimes lately?

Yes, it was running random percentage of a work unit instead of full 100%.
26) Message boards : News : GPU version fix (Message 779)
Posted 27 Mar 2018 by Sergei Chernykh
Post:
There was a serious bug in GPU version: https://github.com/SChernykh/Amicable/commit/3470ed855d244100f37b0b7ab4c912d2b9365a93
Unfortunately, it skipped some numbers in an unpredictable way for "large primes" work units for the last 20 days 9 days. I'll have to reissue all such work units to cover everything missed. The GPU versions for all platforms are already updated.

Sorry for the mess, but it's good that the bug is fixed relatively early, because it was hard to notice.
27) Message boards : Number crunching : Auto-ban faulty hosts (Message 778)
Posted 27 Mar 2018 by Sergei Chernykh
Post:
to start banning pc's with just 2 errors out of 242 workunits seems a bit harsh. What's the procedure for the guy to bring his pc back? In the banning process he had more workunits on his pc that he finished crunching but was NOT allowed to return them to even figure out it the problem was fixed or not, he had to abort them all and move to another project, where the graphics card is working just fine.

It's not harsh, because extremely few computers actually get banned here. He needs to check his GPU, run stress tests and make sure it doesn't crash or give errors, doesn't overheat, and I'll unban it then. "Working just fine" depends on the type of workload. It may be just on the edge for some projects and run fine, but cross the edge and fail sometimes on other projects.
28) Message boards : Number crunching : Auto-ban faulty hosts (Message 776)
Posted 27 Mar 2018 by Sergei Chernykh
Post:
1 error detected in the compilation of "C:\Users\steve\AppData\Local\Temp\OCL2252T1.cl".
Frontend phase failed compilation.

OpenCL.cpp, line 397: Trying to disable 'goto' and build again
01:16:06 (2252): called boinc_finish(0)

please tell me how this is a USER CAUSED ERROR? Because I too could be banned if this is a problem caused by the users!!

That PC has this message in all tasks' logs, including a few hundred valid ones. It's normal: in this case it failed to compile because of a known issue with amd drivers and a workaround was applied, so it compiled and ran fine after that.

But incorrect result was returned for a few tasks out of a few hundred valid tasks. This is a direct indication of unstable hardware. Many similar configurations run with the same message in logs, but without problems (validation failures) on this project.

Only validation failures are counted - it's when a client didn't report any errors on exit, but returned incorrect result. This can jeopardize the whole project's target and can't be tolerated.

Only "Completed, marked as invalid" status is counted for banning.

Because I too could be banned if this is a problem caused by the users!!

No, your computers have 0 "Completed, marked as invalid" tasks.

P.S. There are over 5000 hosts that run Amicable Numbers every day. Only 3 hosts are currently banned, so please don't exaggerate this problem.
29) Message boards : Number crunching : Auto-ban faulty hosts (Message 774)
Posted 25 Mar 2018 by Sergei Chernykh
Post:
I did 1300 good work units and 4 invalid and you banned my computer!!!!!!! BYE!!!

Do you realise this ban was automatic? Unless you fix this PC, it will stay banned.
30) Message boards : Random stuff : Social Numbers (Message 771)
Posted 20 Mar 2018 by Sergei Chernykh
Post:
I would assume that the Amicable Numbers project has a database with the sum of the proper divisors for many numbers.

No, it's not even theoretically possible to save this amount of data. The project only stores found amicable pairs. Social numbers require different search algorithm.
31) Message boards : Number crunching : GPU version: kernel size tuning and less UI lags (Message 769)
Posted 18 Mar 2018 by Sergei Chernykh
Post:
There was not enough GPU memory. Try to close all other programs. Work units that are being issued now require less memory than before, so there is a good chance you won't have this error now.

P.S. You can also try to reduce kernel size.
32) Message boards : Number crunching : >96% of v2.08 aarch64-unknown-linux-gnu (mt) WUs failing (Message 766)
Posted 13 Mar 2018 by Sergei Chernykh
Post:
You'll need a 2 GB swap file for current work units.
33) Message boards : Getting started : how to run on C2070 & K80 (Message 763)
Posted 12 Mar 2018 by Sergei Chernykh
Post:
BOINC didn't recognize these cards on your computers. You can try to reinstall graphics drivers.
34) Message boards : Bug tracker : Computation error at 6 seconds (Message 759)
Posted 9 Mar 2018 by Sergei Chernykh
Post:
MacOS GPU version broke again when the project switched to the new type of work units, sorry for the mess. I'll fix it later today when I have time.
35) Message boards : Random stuff : Command Line Change (Message 757)
Posted 7 Mar 2018 by Sergei Chernykh
Post:
It's a new type of work units (I call them "large prime WUs"). The search now goes through all primes between first and second number in the command line and looks for amicable numbers of the form "n*p" where p is a prime from this range and n*p < 1020.
https://github.com/SChernykh/Amicable/blob/boinc-version-128-bit/Amicable/Amicable.cpp#L131
36) Message boards : Random stuff : Up to date list of project badges (Message 755)
Posted 6 Mar 2018 by Sergei Chernykh
Post:
Added new badge for finding 100,000 amicable pairs:
37) Message boards : Random stuff : Which OS this project support? Also, Can you help me Mapping BOINC community? (Message 754)
Posted 3 Mar 2018 by Sergei Chernykh
Post:
https://boinc.berkeley.edu/projects.php

Here is written too Nvidia/AMD gpu

is incorrect, right?.

Sorry for asking dumb questions.

It's correct. The project supports AMD and NVIDIA GPUs.
38) Message boards : Bug tracker : Computation error at 6 seconds (Message 751)
Posted 3 Mar 2018 by Sergei Chernykh
Post:
Lamplighter55
Can you try again with version 2.09?
39) Message boards : Bug tracker : Computation error at 6 seconds (Message 750)
Posted 3 Mar 2018 by Sergei Chernykh
Post:
MacOS didn't like new OpenCL code:
<program source>:1516:29: error: comparison of integers of different signs: 'ulong' (aka 'unsigned long') and 'int'
if (amicableCandidateIndex >= candidatesDataHighBitOffsets.x) value_ulong |= 0x100000000UL;

I'll fix it ASAP.
40) Message boards : Random stuff : Which OS this project support? Also, Can you help me Mapping BOINC community? (Message 748)
Posted 3 Mar 2018 by Sergei Chernykh
Post:
The project supports Widows, Linux and MacOS: https://sech.me/boinc/Amicable/apps.php
Requirements: 64-bit OS, 2 GB of free memory.
41) Message boards : Random stuff : Report on search up to 2^64 (Message 746)
Posted 27 Feb 2018 by Sergei Chernykh
Post:
https://sech.me/boinc/Amicable/forum_thread.php?id=91
Yes, I also have an analysis of amicable pairs distribution based on the results of this search, which gave me an approximate formula for the amount of amicable pairs below any given number. I'll publish an article describing it soon, when I have more free time. Probably some time in March.
42) Message boards : Number crunching : WUs names - are there different types of WUs? (Message 744)
Posted 22 Feb 2018 by Sergei Chernykh
Post:
In short, WU names are made random because they have to be unique.

amicable_10_20 - app name
20198 - PID of the process that generated this WU
1519206302.310434 - timestamp
177 - number in the batch
43) Message boards : Number crunching : Computers list is gone? (Message 742)
Posted 18 Feb 2018 by Sergei Chernykh
Post:
I try to keep the database from bloating. Even now, hosts.gz is 2.5 MB: https://sech.me/boinc/Amicable/stats/
44) Message boards : Number crunching : Computers list is gone? (Message 740)
Posted 18 Feb 2018 by Sergei Chernykh
Post:
Hosts that weren't active for more than 3 months are automatically deleted.
45) Message boards : Number crunching : Computers list is gone? (Message 738)
Posted 18 Feb 2018 by Sergei Chernykh
Post:
Are you talking about this one: https://sech.me/boinc/Amicable/top_hosts.php ?
Or this one: https://sech.me/boinc/Amicable/hosts_user.php?userid=2516 ?
46) Message boards : News : More than 1000 new amicable pairs found! (Message 734)
Posted 10 Feb 2018 by Sergei Chernykh
Post:
It's a type of amicable pair. Detailed explanation: https://en.wikipedia.org/wiki/Amicable_numbers#Regular_pairs.
Short explanation: first digit is the amount of unique prime factors in the first number, second digit is the amount of unique prime factors in the second number.

In this pair:
- 13, 29, 193, 293, 1979, 5623, 20599 (7 factors) are unique to the first number
- 73, 1249, 798503, 74397311 (4 factors) are unique to the second number
47) Message boards : Bug tracker : Amicable doesn't respect usage limits (Message 731)
Posted 6 Feb 2018 by Sergei Chernykh
Post:
It's better to set the number of CPU cores to use and run only one task at a time. Try setting 2, 3, 4 cores to find which setting doesn't overheat your CPU. Setting the % of CPU time to use sometimes gives an invalid result for WU, and I have no idea why, so I had to turn off this setting.

P.S. Actually, it shouldn't overheat when running Amicable. Amicable uses only integer arithmetic, no heavy SSE/AVX instructions at all. Check you CPU cooler.
48) Message boards : Number crunching : Drop in WU size? (Message 729)
Posted 6 Feb 2018 by Sergei Chernykh
Post:
The speed increase for GPU over CPU depends on how well a WU can be parallelized, but it's hard to predict without actually running each WU. It's even different between various GPU models. CPUs are more stable because they don't run that many parallel threads. That's why WUs were normalized for CPUs.
49) Message boards : Random stuff : Up to date list of project badges (Message 726)
Posted 1 Feb 2018 by Sergei Chernykh
Post:
That's definitely not an e-mail sent by the project. Check "From: " field again. It must have been someone else - free-dc.org, signature.statseb.fr or some other BOINC stats tracking site. You should ask them to fix this.
50) Message boards : Random stuff : Up to date list of project badges (Message 724)
Posted 1 Feb 2018 by Sergei Chernykh
Post:
What Turbo badge?


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