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1) Message boards : Number crunching : Once in a Blue Moon Challenge (Message 151058)
Posted 48 days ago by KylePolanskyProject donor
HyperThreading/SMT performance improvements are mainly in the ability to do work on one thread while another thread is waiting for data to be fetched. This is accomplished by some extras registers that store the state of each thread such that it's very fast switch between threads.

For example, if one thread needs to fetch something from memory, another thread could run computations, and when that thread was finished computing the first thread probably has the data it needs and can continue computing. This leads to a noticable improvement in most applications that have a mix of computation and data manipulation.

However, PrimeGrid is almost entirely computation with very little data fetching. If you were to run PrimeGrid on two threads sharing the same CPU core, each thread would be "fighting" for computation units in the core (there's only a fixed number per core, it's the same with or without SMT). This would lead to extra thread switching. While very fast, this non-zero time thread switch does "waste" time in the sense that it's not used for meaningful computation.

Additionally, any time you have concurrent algorithms in programming, there will be some penalty for synchronizing the data. If two threads write to the same memory location at the same time, the data in that location likely gets corrupted. There are typically locks where one thread writes and the others wait their turn in line to write next. This slowdown can be seen by running a typical multicore program on 2 cores, and noticing it will take slightly longer than half the time of running it on one core (when you might naively expect 2 cores to be exactly twice as far as 1). The extra time is generally all of the data synchronization. With hyperthreading/SMT, you're essentially doubling the amount of worker threads, which leads to double the time wasted on data synchronization.

This is a pretty simplified overview. There are a lot more layers of computer that impact how everything works, but these are some of the pieces that I'm somewhat familiar with.
2) Message boards : Number crunching : Server sent unit to 3 hosts in a short time (Message 148321)
Posted 233 days ago by KylePolanskyProject donor
Congrats on the find!

I noticed this workunit on my DC list and was curious about the 3rd task as well.

I originally felt bad taking the DC away from the other user (at least in the discord #prime-discoveries channel), but after more investigation, it seems we were both given credit on our profiles and TdP double checker leaderboard.


To help future users searching for this information, the task output was:
<primegrid_recovery> This result was abandoned and automatically recovered on server. </primegrid_recovery> <stderr_txt> </stderr_txt>
3) Message boards : Problems and Help : Can't figure out why CPU isn't being used 100% (Message 147346)
Posted 264 days ago by KylePolanskyProject donor
That means you shouldn't run more than 1 MEGA with 4 threads (CPUs),
or 2 MEGAs with 2 threads (CPUs) each. By doing this, your CPUs will be
close to 100% and you'll do at least twice as many MEGA tasks per day.

Since you're running other things (which use L3 too), I'd recommend 1 MEGA with 4 threads.
If you weren't running other things, 2 MEGAs with 2 threads might be slightly faster.


While this is generally good advice for most other CPU apps, I don't believe GFN supports multithreading (except for GFN-21).
4) Message boards : Wieferich and Wall-Sun-Sun Prime Search : New Version Testing (Message 147228)
Posted 268 days ago by KylePolanskyProject donor
Haven't seen any AMD cpus yet, so here's a Windows CPU Multithreaded running an AMD Ryzen 5950X:

> .\WWcpu-win64.exe 18446744013709551615 18446744073709551615 -t 16 WWcpu version 1.03 by Bryan Little and Yves Gallot Compiled Dec 28 2020 with GCC 8.1.0 A Wieferich and WallSunSun prime number search program Based on wwww by Mark Rodenkirch Starting search at: 18446744013709551615 Stopping search at: 18446744073709551615 Detected 32 logical processors. Using 16 threads. Beginning a new search with parameters from the command line ... Workunit time: 291 sec Checksum: 509DE6503B2A6E8E > Get-Content results-WW.txt 509DE6503B2A6E8E > .\WWcpu-win64.exe 1 6e10 -t 16 WWcpu version 1.03 by Bryan Little and Yves Gallot Compiled Dec 28 2020 with GCC 8.1.0 A Wieferich and WallSunSun prime number search program Based on wwww by Mark Rodenkirch START below minimum. Starting search at 127 Starting search at: 127 Stopping search at: 60000000000 Detected 32 logical processors. Using 16 threads. Beginning a new search with parameters from the command line ... Workunit time: 224 sec Checksum: 8B77D2DA053842DD > Get-Content results-WW.txt 127 is a Wieferich special instance (+1 +9 p) 127 is a WallSunSun special instance (+0 +13 p) ... 59755020131 is a Wieferich special instance (-1 -487 p) 59856984349 is a Wieferich special instance (-1 -322 p) 8B77D2DA053842DD > .\WWcpu-win64.exe 227630e10 227636e10 -t 16 WWcpu version 1.03 by Bryan Little and Yves Gallot Compiled Dec 28 2020 with GCC 8.1.0 A Wieferich and WallSunSun prime number search program Based on wwww by Mark Rodenkirch Starting search at: 2276300000000000 Stopping search at: 2276360000000000 Detected 32 logical processors. Using 16 threads. Beginning a new search with parameters from the command line ... Workunit time: 241 sec Checksum: 6522CBC4CA2E4CFF > Get-Content results-WW.txt 2276306935816523 is a Wieferich special instance (-1 -3 p) 6522CBC4CA2E4CFF > .\WWcpu-win64.exe 338772621946054253 338772681946054253 -t 16 WWcpu version 1.03 by Bryan Little and Yves Gallot Compiled Dec 28 2020 with GCC 8.1.0 A Wieferich and WallSunSun prime number search program Based on wwww by Mark Rodenkirch Starting search at: 338772621946054253 Stopping search at: 338772681946054253 Detected 32 logical processors. Using 16 threads. Beginning a new search with parameters from the command line ... Workunit time: 255 sec Checksum: 589A69274A6AB5A8 > Get-Content results-WW.txt 338772621946054253 is a WallSunSun special instance (+0 +91 p) 589A69274A6AB5A8


Here's another Windows NVidia GPU datapoint for performance comparison:

> .\WWocl-win64.exe 18446744013709551615 18446744073709551615 WWocl version 1.03 by Bryan Little and Yves Gallot Compiled Dec 27 2020 with GCC 8.1.0 A Wieferich and WallSunSun prime number search program Based on wwwwcl by Mark Rodenkirch and primesieve by Kim Walisch Starting search at: 18446744013709551615 Stopping search at: 18446744073709551615 init_data.xml not found, using device 0. GPU Info: Name: GeForce GTX 1080 Vendor: NVIDIA Corporation Driver: 460.89 Compute Units: 20 Beginning a new search with parameters from the command line Starting search... ... Workunit complete. Average speed: 38.64 Million primes per second. Checksum: 509DE6503B2A6E8E > Get-Content results-WW.txt 509DE6503B2A6E8E > .\WWocl-win64.exe 1 6e10 WWocl version 1.03 by Bryan Little and Yves Gallot Compiled Dec 27 2020 with GCC 8.1.0 A Wieferich and WallSunSun prime number search program Based on wwwwcl by Mark Rodenkirch and primesieve by Kim Walisch START below minimum. Starting search at 127 Starting search at: 127 Stopping search at: 60000000000 init_data.xml not found, using device 0. GPU Info: Name: GeForce GTX 1080 Vendor: NVIDIA Corporation Driver: 460.89 Compute Units: 20 Beginning a new search with parameters from the command line Starting search... ... Workunit complete. Average speed: 87.04 Million primes per second. Checksum: 8B77D2DA053842DD > Get-Content results-WW.txt 127 is a Wieferich special instance (+1 +9 p) 127 is a WallSunSun special instance (+0 +13 p) ... 59755020131 is a Wieferich special instance (-1 -487 p) 59856984349 is a Wieferich special instance (-1 -322 p) 8B77D2DA053842DD > .\WWocl-win64.exe 227630e10 227636e10 WWocl version 1.03 by Bryan Little and Yves Gallot Compiled Dec 27 2020 with GCC 8.1.0 A Wieferich and WallSunSun prime number search program Based on wwwwcl by Mark Rodenkirch and primesieve by Kim Walisch Starting search at: 2276300000000000 Stopping search at: 2276360000000000 init_data.xml not found, using device 0. GPU Info: Name: GeForce GTX 1080 Vendor: NVIDIA Corporation Driver: 460.89 Compute Units: 20 Beginning a new search with parameters from the command line Starting search... ... Workunit complete. Average speed: 51.42 Million primes per second. Checksum: 6522CBC4CA2E4CFF > Get-Content results-WW.txt 2276306935816523 is a Wieferich special instance (-1 -3 p) 6522CBC4CA2E4CFF > .\WWocl-win64.exe 338772621946054253 338772681946054253 WWocl version 1.03 by Bryan Little and Yves Gallot Compiled Dec 27 2020 with GCC 8.1.0 A Wieferich and WallSunSun prime number search program Based on wwwwcl by Mark Rodenkirch and primesieve by Kim Walisch Starting search at: 338772621946054253 Stopping search at: 338772681946054253 init_data.xml not found, using device 0. GPU Info: Name: GeForce GTX 1080 Vendor: NVIDIA Corporation Driver: 460.89 Compute Units: 20 Beginning a new search with parameters from the command line Starting search... ... Workunit complete. Average speed: 43.72 Million primes per second. Checksum: 589A69274A6AB5A8 > Get-Content results-WW.txt 338772621946054253 is a WallSunSun special instance (+0 +91 p) 589A69274A6AB5A8
5) Message boards : Wieferich and Wall-Sun-Sun Prime Search : New Version Testing (Message 147152)
Posted 269 days ago by KylePolanskyProject donor
Windows CPU Singlethreaded results:
CPU: Intel Core i9-10900K

> .\WWcpu-win64.exe 18446744013709551615 18446744073709551615 WWcpu version 1.03 by Bryan Little and Yves Gallot Compiled Dec 28 2020 with GCC 8.1.0 A Wieferich and WallSunSun prime number search program Based on wwww by Mark Rodenkirch Starting search at: 18446744013709551615 Stopping search at: 18446744073709551615 Running single threaded. Beginning a new search with parameters from the command line ... Workunit time: 4808 sec Checksum: 509DE6503B2A6E8E > Get-Content results-WW.txt 509DE6503B2A6E8E > .\WWcpu-win64.exe 1 6e10 WWcpu version 1.03 by Bryan Little and Yves Gallot Compiled Dec 28 2020 with GCC 8.1.0 A Wieferich and WallSunSun prime number search program Based on wwww by Mark Rodenkirch START below minimum. Starting search at 127 Starting search at: 127 Stopping search at: 60000000000 Running single threaded. Beginning a new search with parameters from the command line ... Checksum: 8B77D2DA053842DD > Get-Content results-WW.txt 127 is a Wieferich special instance (+1 +9 p) 127 is a WallSunSun special instance (+0 +13 p) ... 59856984349 is a Wieferich special instance (-1 -322 p) 8B77D2DA053842DD > .\WWcpu-win64.exe 227630e10 227636e10 WWcpu version 1.03 by Bryan Little and Yves Gallot Compiled Dec 28 2020 with GCC 8.1.0 A Wieferich and WallSunSun prime number search program Based on wwww by Mark Rodenkirch Starting search at: 2276300000000000 Stopping search at: 2276360000000000 Running single threaded. Beginning a new search with parameters from the command line ... Workunit time: 3794 sec Checksum: 6522CBC4CA2E4CFF > Get-Content results-WW.txt 2276306935816523 is a Wieferich special instance (-1 -3 p) 6522CBC4CA2E4CFF > .\WWcpu-win64.exe 338772621946054253 338772681946054253 WWcpu version 1.03 by Bryan Little and Yves Gallot Compiled Dec 28 2020 with GCC 8.1.0 A Wieferich and WallSunSun prime number search program Based on wwww by Mark Rodenkirch Starting search at: 338772621946054253 Stopping search at: 338772681946054253 Running single threaded. Beginning a new search with parameters from the command line ... Workunit time: 4030 sec Checksum: 589A69274A6AB5A8 > Get-Content results-WW.txt 338772621946054253 is a WallSunSun special instance (+0 +91 p) 589A69274A6AB5A8
6) Message boards : Wieferich and Wall-Sun-Sun Prime Search : New Version Testing (Message 147145)
Posted 269 days ago by KylePolanskyProject donor
Here's another Windows NVidia GPU result:

> .\WWocl-win64.exe 18446744013709551615 18446744073709551615 WWocl version 1.03 by Bryan Little and Yves Gallot Compiled Dec 27 2020 with GCC 8.1.0 A Wieferich and WallSunSun prime number search program Based on wwwwcl by Mark Rodenkirch and primesieve by Kim Walisch Starting search at: 18446744013709551615 Stopping search at: 18446744073709551615 init_data.xml not found, using device 0. GPU Info: Name: Quadro P400 Vendor: NVIDIA Corporation Driver: 451.48 Compute Units: 2 Resuming search from checkpoint. Current: 18446744045170737540 Starting search... ... Workunit complete. Average speed: 2.90 Million primes per second. Checksum: 509DE6503B2A6E8E > .\WWocl-win64.exe 1 6e10 WWocl version 1.03 by Bryan Little and Yves Gallot Compiled Dec 27 2020 with GCC 8.1.0 A Wieferich and WallSunSun prime number search program Based on wwwwcl by Mark Rodenkirch and primesieve by Kim Walisch START below minimum. Starting search at 127 Starting search at: 127 Stopping search at: 60000000000 init_data.xml not found, using device 0. GPU Info: Name: Quadro P400 Vendor: NVIDIA Corporation Driver: 451.48 Compute Units: 2 Beginning a new search with parameters from the command line Starting search... ... Workunit complete. Average speed: 6.28 Million primes per second. Checksum: 8B77D2DA053842DD > .\WWocl-win64.exe 227630e10 227636e10 WWocl version 1.03 by Bryan Little and Yves Gallot Compiled Dec 27 2020 with GCC 8.1.0 A Wieferich and WallSunSun prime number search program Based on wwwwcl by Mark Rodenkirch and primesieve by Kim Walisch Starting search at: 2276300000000000 Stopping search at: 2276360000000000 init_data.xml not found, using device 0. GPU Info: Name: Quadro P400 Vendor: NVIDIA Corporation Driver: 451.48 Compute Units: 2 Beginning a new search with parameters from the command line Starting search... ... Workunit complete. Average speed: 3.94 Million primes per second. Checksum: 6522CBC4CA2E4CFF > .\WWocl-win64.exe 338772621946054253 338772681946054253 WWocl version 1.03 by Bryan Little and Yves Gallot Compiled Dec 27 2020 with GCC 8.1.0 A Wieferich and WallSunSun prime number search program Based on wwwwcl by Mark Rodenkirch and primesieve by Kim Walisch Starting search at: 338772621946054253 Stopping search at: 338772681946054253 init_data.xml not found, using device 0. GPU Info: Name: Quadro P400 Vendor: NVIDIA Corporation Driver: 451.48 Compute Units: 2 Beginning a new search with parameters from the command line Starting search... ... Workunit complete. Average speed: 3.30 Million primes per second. Checksum: 589A69274A6AB5A8
7) Message boards : Wieferich and Wall-Sun-Sun Prime Search : New Version Testing (Message 147143)
Posted 269 days ago by KylePolanskyProject donor
I'll reserve Windows CPU Singlethreaded
8) Message boards : Number crunching : WW testing (Message 144889)
Posted 329 days ago by KylePolanskyProject donor
In testing an old AMD Radeon HD 6750, I got the following error:

line 18: error: can't enable all OpenCL extensions or unrecognized OpenCL extension #pragma OPENCL EXTENSION cl_khr_int64_base_atomics : enable ^ line 222: error: function "atom_add" declared implicitly atom_add( &checksum[0], w_quot & UINT32_MAX ); ^ 2 errors detected in the compilation


In talking with mfl0p on Discord, it appears that the graphics card must support the "cl_khr_int64_base_atomics" (64 bit atomic operations) OpenCL extension.

I assume this requirement will be better documented when the project goes live, just wanted to put a note here incase anyone else happens to come across this issue.
9) Message boards : Number crunching : WW testing (Message 144886)
Posted 330 days ago by KylePolanskyProject donor
I'm not a mac user, but I decided to give this a try on a friend's mac mini to see what would happen.

Running binary from commit 84a5282 I got the following error:

./WW_opencl_macintel64 461168595e10 461168602e10 -debug WWocl version 1.0 by Bryan Little Compiled Oct 29 2020 with GCC Apple LLVM 12.0.0 (clang-1200.0.32.2) A Wieferich and WallSunSun prime number search program Based on wwwwcl by Mark Rodenkirch and primesieve by Kim Walisch Debug info enabled. END exceeds maximum. Stopping search at 4611686018427387904 Starting search at: 4611685950000000000 Stopping search at: 4611686018427387904 init_data.xml not found, using device 0. GPU Info: Name: Intel(R) UHD Graphics 630 Vendor: Intel Inc. Driver: 1.2(Aug 31 2020 22:24:18) Compute Units: 24 Compiling clearn... Kernel workgroup size: 256 Compiling wieferich... Error on buildProgram RequestingInfo Build Log for wieferich_program: <program source>:117:15: warning: comparison of integers of different signs: 'long' and 'ulong' (aka 'unsigned long') if (xb_rem >= thePrime) { xb_rem -= thePrime; } ~~~~~~ ^ ~~~~~~~~ <program source>:169:14: warning: comparison of integers of different signs: 'long' and 'ulong' (aka 'unsigned long') if (xb_rem >= thePrime) { xb_rem -= thePrime; } ~~~~~~ ^ ~~~~~~~~ error: undefined reference to `_Z8atom_addPVU8CLglobalmm()' error: backend compiler failed build. CL_BUILD_PROGRAM_FAILURE


This error is pretty cryptic, so i'm not sure if this is an error with the binary, using integrated GPUs, or even a driver/opencl install error. I suspect BOINC won't run on integrated GPUs so it's likely not a valid test, but decided to post here incase it helps out.

Other computer stats:
Model: Mac mini (2018)
Processor: 3.2 GHz 6-Core Intel Core i7
OS: Version 10.15.7
Graphics: Intel UHD Graphics 630 1536MB
10) Message boards : Number crunching : WW testing (Message 144500)
Posted 340 days ago by KylePolanskyProject donor
Here's more Linux CPU Singlethreaded Results:

1) ./WWcpu-linux64 461168595e10 461168602e10
Workunit time: 14361 sec
Checksum: 67029FBFBC1AEFB0

2) ./WWcpu-linux64 1 6e10
Workunit time: 11863 sec
Checksum: 2F32CAD23BA5B1CA

3) ./WWcpu-linux64 227630e10 227636e10
Workunit time: 12807 sec
Checksum: B8B040FA3813FEB2


Computer Info:
CPU: Intel(R) Xeon(R) CPU E5-2673 v4 @ 2.30GHz
OS: 20.04.1 LTS (Focal Fossa)

Notes: Ran inside a pod on AKS (Azure Kubernetes Service) Version 1.17.9, Node Size Standard_D2s_v3


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