[Feat]: GetLines()

[andy-wrks]

What is your idea?

Currently there's

• GetLine() for single lines
• GetAllLines() for all lines in the file

A common use case is to get all lines of a specific type, like all IfcElements or all IfcPropertySingleValues. This can result in tens of thousands of lines. Getting them all in a loop as single lines has a lot of overhead. It's lots of calls to WASM which has inut/output overhead.

What would be very useful:
A GetLines() method that takes an Array or Set of expressIds and returns the line objects as an Array or Map. That way, only one call to WASM would have to be made instead of tens of thousands.

Thanks for considering this and thanks for the great work :-)

[andy-wrks]

I'll document some numbers from my performance tests here and I'd be happy to test again, if the proposed method should get implemented. I wanted to get a feeling about the WASM i/o overhead. However, I soon realized that GetAllLines() does only return expressIds, not the full line objects. So there was nothing to really compare the performance of single GetLine() calls against. Still, some numbers:

Model 1 is 174 MB and has around 2 300 000 lines in total, of which 774 480 IfcPropertySingleValues were fetched from web-ifc

• Time to get all lines (774k WASM calls) --> 4551 ms (4.5 s)

Model 2 is 535 MB and has around 8 500 000 lines in total, of which 1 419 526 IfcPropertySingleValues were fetched from web-ifc

• Time to get all lines (1.4m WASM calls) --> 7727 ms (7.7 s)

Times were measured in Chrome on an older i7 CPU in a kind of "best of 10 attempts" manner.
Firefox was consistently slower, although it was consistently 15-20% faster than Chrome in initially parsing the model.

I hope these numbers can be of interest in finding out how much time is actually being spent "inside" WASM and how much overhead is added through hundreds of thousands of individual method calls and i/o conversions.