Remove null checks before GetValueOrDefault

[jamesqo]

Separated from PR #2318. Free perf.

[stephentoub]

Free perf

Can you please share your perf tests and results? What's the impact when all values are null? When some are null? When none are null? Etc.

[stephentoub]

cc: @VSadov

[mikedn]

Can you please share your perf tests and results? What's the impact when all values are null? When some are null? When none are null? Etc.

This approach should be faster if the number of nulls in the source is low. GetValueOrDefault "cheats" and returns the value field without actually checking hasValue, that avoids a bunch of things: a memory load, a 0 test and a branch.

If the number of nulls is high then this will likely be slower, especially in the decimal case. add operations that previously were simply skipped now how to be done.

Let's see what benchmarks will say :)

[jamesqo]

Just finished writing the test. Here is the test (ideone), here are the old results, here are the new ones. What are your opinions?

[stephentoub]

Thanks for sharing. Based purely on the data you shared, I don't think this is a change we should take. Where there was an improvement, it was typically significantly less than 1%, and there were plenty of regressions, including several greater than 1%, and one almost 5%.

[jamesqo]

Alright, I understand. Thanks.