standalone compilation fails

[srlantz]

GCC has started complaining about a type mismatch in Event.cc. The line in question is

SVector6 &c = h.error_nc();

GCC reports that the type of the RHS as SMatrixSym33&, not SVector6&. The error can be "fixed" by overruling C++ type safety,

SVector6 &c = reinterpret_cast<SVector6&>(h.error_nc());

@dan131riley traced the difference to the PR from Mario that was merged Jan. 17, cms-sw#47106. It changes the type of the hit error matrix returned by error_nc() in Hit.h.

I imagine the right way to fix this in Event.cc is to change the type of c to match the new type, and to subscript c properly in the subsequent code. However, there could be something simpler/kludgier that still preserves type safety, maybe at the cost of making a copy. Probably @osschar should make the call here.

The containing function kludge_cms_hit_errors() appears to be little used in any case.

[osschar]

Phew ... this is super old stuff, I don't even remember why we have Event::kludge_cms_hit_errors() (where this thing happens). I think this was from Kevin, maybe?

Proper fix is to use the new type -- SMatrix might even provide the same array access. Otherwise index order is for bottom left triangle.

I'd say an even more proper fix is to remove the kludge function in Event and config in ConfigStandalone --- unless somebody remembers why it was there in the first place :)

[dan131riley]

The PR by @osschar (7 years ago) says:

• Option to set a lower limit on hit errors (15mum in xy and 30mum in z) ... this is done under --kludge-cms-hit-errors option.

Probably not important for what the standalone mkFit is currently used for, so removal should be ok.

[srlantz]

OK, I'll prepare a PR to sweep out the clutter.

[srlantz]

Made PR cms-sw#47476 directly to cms-sw - actually I meant to make a PR to trackreco first, just for previewing, but apparently GitHub's default for this repo is to make the PR to upstream. Anyway, it shouldn't be a controversial commit.

[osschar]

Yup, that's exactly it -- thank you! :)