Discussion Thread for the Continuous GW Search known as O2MD1 (now O2MDF - GPUs only)

In this message in the O2AS discussion thread, I posted data for crunch times for the V1.09 GPU app when running on 4 different CPU/GPU combinations for task multiplicities up to 4x.  The results showed significant improvement in output (ie reduction in secs/task) in all cases when using the higher multiplicities.  With the advent of the O2MD1 search using GPUs, I'm keen to get similar information for the new V1.10 app.  It's a different type of search (directed at specific targets rather than covering the whole sky) so performance is likely to be quite different.

I decided to use 2 hosts that were used in the previous tests, the Q6600/RX 460 and the i5-3470/RX 570 which were the 1st and 4th from the previous list.  Both hosts got work for frequencies around the 215Hz mark so well above the low end values that were reported by others earlier on.

I found these tasks were able to crunch very quickly.  There are already enough returned results to provide some information about expected crunch times so I'll give details here using the same format (columns, abbreviations, etc) as previously.  Each concurrent GPU task had access to the support of a full CPU core.

CPU / GPU (Cores / Threads / GHz)    Tsks     Multi   Pnd  Val   Inc   Inv   Err   Productivity values (secs/task)
=================================    ====     =====   ===   ===   ===   ===   ===   ===============================
Q6600 / RX 460 (4C / 4T / 2.4 GHz)     20     1,2,3     20    0     0     0     0   1300s,  975s,  712s
i5-3470/RX 570 (4C / 4T / 3.2 GHz)     28     1,2,3,4   28    0     0     0     0    586s,  380s,  330s,  312s

Only small numbers were crunched at the lowest multiplicities - just enough to get a basic value for the crunch time.  The bulk of the results were at 3x for the RX 460 and 4x for the RX 570.  The crunch times seemed to become rather more variable for the 570 at 4x so I didn't try 4x for the 460 or anything higher than 4x for the 570.  There was good consistency in the times for both hosts up to 3x.

The CPU time component for each task was surprisingly constant irrespective of multiplicity.  I guess that suggests a fairly constant amount of CPU work per task which shows as a relatively uniform time if there's always a full core available.  The slower CPU will use more time to provide that constant amount of work.  Here is a small table to show the typical values of elapsed time/CPU time for both hosts at the multiplicities used.

GPU Type     Multi     Elapsed     CPU     Tsks
========      =====     =======     ===     ====
RX 460         1x         1300      496        1
RX 460         2x         1950      509        4
RX 460         3x         2135      452       15
RX 570         1x          586      278        1
RX 570         2x          760      278        4
RX 570         3x          990      286        3
RX 570         4x         1246      310       20

All results so far are pending.  Since it may be a while before any validations are performed, I've switched the hosts back to FGRPB1G until it becomes clear that validation is OK.  I don't see much point in crunching more until we see how validation goes.