what are formula groups in Calc?

File > Properties > Statistics displays “formula groups.” What are they?

A formula group is a continuous range in a column that contains the same token sequence.
For instance if cells B1 through B3 each contain a formula of =A1 + 3 through =A3 + 3, that would be one formula group.

The document property is the total of all such ranges found on all sheets.

Thank you. Any thoughts about why it would be helpful to know how many formula groups in a spreadsheet?

A thought? Yes, Knowledge? No. The thought that’s probably wrong:
Technically the formula for a range of (say) 1000 cells only needs to be saved once together with a bit of information about the range (5 integer numbers in the way a RangeAddress is treated by the API). It’s like you do it: Enter the formula once and expand the range to apply it as needed.
However, the OpenDocument specifications for .ods don’t use this way to efficiency.
Why? Donno! @drewjensen might know?

Honestly - I didn’t know the property existed on the Statistics page of the Property dialog till reading your question here.

So - at the moment the best I can offer is a reference to this property during a presentation at the 2015 LibreOffice conference. “Improved Automated Error Checking (pg 12)”

Also asked a few other people this same question, just this morning - will let you know what I hear

@Lupp “might know” what? Why the ODF spec ended up the way it did? No.

Drew, I respect your ability to find such a reference.
It seems like a round-about way to find out about user error.

Computation of formula groups can be parallelized more efficiently since LibreOffice 6.4: commit “Thread a group of formula-groups together if possible”