Re: Why does Ada compile slower than Python?

[olivermkellogg@gmail.com]

On Tuesday, October 3, 2017 at 11:08:59 PM UTC+2, Victor Porton wrote:
> Victor Porton wrote:
> [...]
> According this test (valid only for very short programs) compiling Ada is 
> slower only two times.
> 
> Maybe I was under a wrong impression, because I got this impression when I 
> compiled tens of Ada files in a row and my brain was focused on total 
> compilation time rather than compilation time for one file?
> 
> Is GNAT really much slower than Python? or was it a false impression?

When compiling many interdependent packages GNAT is definitely slower than it could be. This has to do with the fact that GCC/GNAT can only handle one file at a time. E.g. if you provide 100 files on a single gcc command line then gcc loads and compiles each file separately as though you were providing 100 commands with one file per command.
Some years ago I had started an experiment to add AST (abstract syntax tree) caching to GNAT and had gotten as far as the Ada frontend (GNAT trees); however, the major effort for making this work is in the later stages of the compiler (GNU trees, etc).

Oliver