Make Show Detectors multi-threaded

[Stuart Campbell]

If you right click on a workspace and select "Show Detectors" then this can take a while (around 20-30 seconds for HYSPEC).

Looking at 'top' it looks like this calculation is single threaded.

[Nick Draper]

Moved to milestone 2.4

[Nick Draper]

Moved at the code freeze for release 2.4

[Nick Draper]

Moved to r2.6 at the end of r2.5

[Nick Draper]

Moved to backlog at the code freeze for R2.6

[Nick Draper]

Bulk move to assigned at the introduction of the triage step

[Federico Montesino Pouzols]

"Show detectors" parallelized with an OpenMP loop, re #5675

Changeset: 3638d676b607256db0a5a98bc9d74b9d0d3a5910

[Federico M Pouzols]

The show detectors loop is now parallel and working fine. But it is running too fast on my computer (around 1/2 a second with this HYSPEC dataset, or WISH, as available in the systemtests repo). Run times are around 0.5-0.55 s. Looking for a data file with many more detectors, to see if we can confirm any significant speedup...

[Federico M Pouzols]

Now I tried with some MERLIN data files. These have 69632 detectors which is enough to start noticing a bit of speedup.

The run times (just 5 repetitions) are in the following ranges (s):

• Without parallel loop: 2.84-2.99
• With parallel loop: 1.90-1.96

So I'll take this as sufficient evidence that it is not only working but also running faster for large (many detectors) datasets.

This has been run on a debian virtual machine that uses half of my i7 processor. Not as great results as it can sometimes be with OpenMP but still a decent speedup.

If you'd like to test this with similar data, from an ISIS windows workstation you can get MERLIN data here:
Isis\inst$\NDXPOLARIS\Instrument\data\

[Andrei Savici]

I am using Ubuntu 14.04. I loaded an empty instrument (TOPAZ), then tried show detectors. It is extremely slow (I stopped it after 40 minutes), because it keeps outputting "QPixmap: It is not safe to use pixmaps outside the GUI thread" message for every pixel (millions)

[Federico Montesino Pouzols]

Don't call QtGUI methods (setText) outside the GUI thread, Re #5675

Changeset: 206c283a09fb16789d4ce816117bc58da775c76e

[Federico M Pouzols]

Oops, my bad. I had left the setText() calls inside the multithreaded loop, and those cannot be safely called outside of the normal Qt GUI thread. Somehow I hadn't got those warning messages.

Now it should be working safely, at the cost of a bit of overhead. Actually, it seems that that overhead has been compensated by a few other minor changes, and it even looks like splitting the loop into two had a positive effect. The new run times for the same 69632 detectors are:

• without parallel loop: 2.57-2.60
• with parallel loop: 1.35-1.38

[Andrei Savici]

Merge remote-tracking branch 'origin/feature/5675_multithreaded_show_detectors'

Full changeset: ​29660a278d285a7a234f3c7fdb48088e27f8c7ba

[Andrei Savici]

A similar speed up was observed on TOPAZ (from 40 seconds to 20)

[Stuart Campbell]

This ticket has been transferred to github issue ​6521