New versions of StarAlignment and ImageIntegration

[stargazercb]

Hi Juan,

this is really great stuff and a big improvement ! Thanks !

On a side-note: On my Linux PC (Fedora 25, x86_64, 4 cores on 1 socket), StarAlignment launches 5 parallel threads while ImageIntegation correctly launches 4 parallel threads.

IMHO it should be 4 processes on a 4-core system, right ?

Tools like nproc, lscpu and /proc/cpuinfo correctly report 4 cores on this system.

Am I missing something or could there be a small issue int he counting of CPUs ?

Many thanks,

Michael.

[Juan Conejero]

Hi Michael,

Am I missing something or could there be a small issue int he counting of CPUs ?

Not at all, of course the number of logical processors available is correctly detected on all platforms.

This is the expected behavior. By default, StarAlignment uses a 20% more worker threads than the number of processors available. This is what we call thread overload. In my intensive tests before releasing the new version of SA, a moderate thread overload has shown small performance improvements. The reason is probably that if there are some spare threads available, they can be fired up as soon as other threads start waiting for I/O completion. In this way thread overload reduces idle wait states and allows to exploit the available processing power somewhat more. This technique only works in some cases for tasks where relatively long I/O operations represent a significant part of the total work.

You can control thread overload with the fileThreadOverload parameter, which can be changed by editing an instance's source code (click the Edit Instance Source Code button on the tool's window, or select the same option by right-clicking on a process icon). Set fileThreadOverload=1 to disable thread overload. The default values are 1.0 for ImageIntegration and 1.2 for StarAlignment.

[stargazercb]

Hi Juan,

thanks for the clarification ! Makes sense !

The parallelization feature is really great. Love it. Much faster than before...

Michael.

[Jules]

Juan

Thanks. my star alignment work so quickly now I thought it had failed LOL.

Regards

Julian

[Alfredo Beltran]

Juan

Based on this thread I have the following questions. Given parallelization takes advantage of several working threads, would it be better to have a very fast processor with 4-cores & 8-threads as the i7-7700k (4.2 - 4.5 GHz clock), or an 8-cores & 16 threads as the new AMD Ryzen 7 1700 (3.2 - 3.6 GHz clock) or the Xeon E5-2620 v4 (2.10 - 3.00 GHz) ? In other words, would there be more benefit from the faster processor with 4-cores than with a slower 8-cores processor?

On he other hand, since now this updated Pixinsight processes use more RAM, would it be a huge improvement to have faster RAM?