DetectorChecksum.cpp: fix a typo

[veprbl]

BEGINRELEASENOTES

• A typo was fixed in the string representation used for checksum calculation. Checksums reported by DD4hepDetectorChecksum plugin will change.

ENDRELEASENOTES

[github-actions]

Test Results

       6 files         6 suites   6h 11m 19s ⏱️
   356 tests    350 ✔️ 0 💤   6 ❌
1 058 runs  1 044 ✔️ 0 💤 14 ❌

For more details on these failures, see this check.

Results for commit 262c20c.

♻️ This comment has been updated with latest results.

[andresailer]

So in the vein of "there are no trivial changes" this changes the checksum calculation.

[veprbl]

Fair point. My understanding was that the feature was experimental. Also, it's not clear that avoiding false negatives is part of the contract here, users should expect checksums mismatch for no apparent reason. In any case, I've added changelog notice, then a decision can be made when and if to merge this.

[andresailer]

Maybe we should have a runtime flag (Environment variable) that makes this switch, and then people can check if the checksum is actually due to our change here, or something else? And in the next version, we make this the default.

[veprbl]

I would assume that users need to be switched to the latest checksumming version ASAP. Supporting calculating with an older algorithm variants is a fine idea. I can look into implementing this.

[MarkusFrankATcernch]

@wdconinc
Hi Wouter,
AFAIK you are the only users of the detector checksum up to now. Could you comment if we can merge this one or not.
Clearly it would invalidate all existing checksums, but there are also reasons of beauty ;-)

[wdconinc]

Our reasons for the checksum are consistency usually within the same version of dd4hep, i.e. making sure that the same geometry was used on simulation and reconstruction, but usually within the same environment and with the same version of dd4hep. I think we would have no problem with changing the checksum with this PR.

I hope someone ran a spell-check so we don't find another typo the day after merging this... ;-)

[MarkusFrankATcernch]

@wdconinc Thanks a lot Wouter. I will then fix the tests and update the repository.

[MarkusFrankATcernch]

Changes incorporated in PR: #1201