Re: [boost] Interest in updated expression template library?

Subject: Re: [boost] Interest in updated expression template library?
From: Larry Evans (cppljevans_at_[hidden])
Date: 2017-01-11 03:00:03

On 01/10/2017 04:22 PM, Mathias Gaunard wrote:
> On 10 January 2017 at 20:07, Zach Laine <whatwasthataddress_at_[hidden]>
> wrote:
>
>>
>> I agree with all of these complaints.  This is in fact why I wrote Yap.
>> The compile times are very good, even for an obnoxious number of terminals
>> (thousands), and there is no memory allocated at all -- or did you mean
>> compiler memory usage?  I haven't looked at that.
>>
>
> Compiler memory usage of course.
> When a TU takes 4GB to compile or more, it leads to lots of problems, even
> if RAM is cheap and you could put hundreds of gigabytes in your build
> server.

Zach, w.r.t. compile-time benchmarking,
Louis has a compiler benchmark library here:

https://github.com/ldionne/metabench

I did have a brief look at it; however, I didn't see an easy way
to vary parameters of the benchmark, for example, the size of
expressions, and compare the results (it uses embedded ruby, and
I couldn't figure out from that how to do what I want).

Instead, I resorted to gmake for loops, as shown here:

https://github.com/cppljevans/spirit/blob/get_rhs/workbench/x3/rule_defns/Makefile#L97

resulting in output shown here:

https://github.com/cppljevans/spirit/blob/get_rhs/workbench/x3/rule_defns/bench.tmp

Interestingly enough, the method that performed worse was the
one (RULE2RHS_CTX_LIST) which stored the rule2rhs information
in the context.  In contrast, the GET_RHS_CRTP stored this
information by overloading functions generated by macros.
What's interesting is that, based on what Brook Milligan says
in his message, proto uses a context as well, but your library
uses a set of function overloads.

With regard to the gmake method of comparing compiler times,
I realize that's sorta kludgy, and, years ago, I used a series
of python programs to do the equivalent.  I you find the
gmake-for-loop method unacceptable, I can try to find the
python method instead.

HTH.

-regards,
Larry