fix: A bug in the Triplet finding algorithm

[konradkusiak97]

As we found out with @krasznaa, there was a bug in the current implementation of the Sycl Seedfinder algorithm. It came out in a particular case when the first part of the algorithm - the Duplet finding, didn't find any duplets. In this scenario, the Triplet finding was running forever and the code didn't terminate.

The problem appeared inside the loop of the Triplet finding.

In the current implementation, finding triplets is splitted into several parts to limit the memory allocations on the GPU. The range of the particular iteration is taken from the firstMiddle and lastMiddle indices. The current logic follows somewhat those steps:

firstMiddle = lastMiddle = 0
while  firstMiddle < MiddleSPs 
   do 
     ++lastMiddle                  // until maxMemory is reached
     numThreads = calcThreads()    // calculate the number of threads for the GPU kernel
     if numThreads != 0:
        tripletSearch(numThreads)
    else: 
        continue
    firstMiddle = lastMiddle

Currently, the increment of the lastMiddle index is performed under the condition. This condition is not satisfied if there are 0 Duplets found and therefore both firstMiddle and lastMiddle stay always 0.

The fix for this issue is to increment the lastMiddle index even when there are 0 numThreads calculated and then continue to the next iteration.

[krasznaa]

@paulgessinger, why is the CI not starting on Konrad's PR? It was not starting on his previous PR either, until I started pusing some of my own commits to it. 😕

[paulgessinger]

@krasznaa weird. I think it should, since @konradkusiak97 is not a first-time contributor anymore, so that should be not the problem. Very strange.

[codecov]

Codecov Report

Merging #1025 (4dc8095) into main (6f3abdd) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main    #1025   +/-   ##
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  Coverage   48.62%   48.62%           
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  Files         337      337           
  Lines       17334    17334           
  Branches     8192     8192           
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  Hits         8428     8428           
  Misses       3164     3164           
  Partials     5742     5742           

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[robertlangenberg]

@krasznaa CI ran through now, if this change looks good, please approve and this can go in

[krasznaa]

Ohh, yes. I'm fully on board with this. 👍