[thechao]

Preprocess your source 'cat' the results together; then, hand off to the compiler. On a 2015 MacBookPro I've seen upwards of 100kloc/s. Probably average 30--60kloc/s. With ccache my 5mloc code base takes as little as 300ms to do incremental compile & relink.

Another thing is to rely on the preprocessor for code generation; then you're dealing with memory-speed elaboration of the AST, rather than reading off of disk.

[dibanez]

I did the single file trick for the small library that I control, as a configure option. It definitely does help, 2X speedup in serial compile time typically. however, you lose the ability to compile in parallel, which with my hardware gives a 16X speedup, so for now parallel compiles are the winner.