D for scientific computing

[Rob T]

On Thursday, 24 January 2013 at 10:17:50 UTC, Walter Bright wrote:
> On 1/23/2013 6:36 PM, Rob T wrote:
>> BTW the D version of my sqlite3 lib is at least 1/3 smaller 
>> than the C++
>> version, and not only is it smaller, but it is far more 
>> flexible due to the use
>> of templates (I just could not make much use out of C++ 
>> templates). A reduction
>> like that is very significant. For large projects. it's a 
>> drastic reduction in
>> development costs and perhaps more so in long term maintenance 
>> costs.
>
> Interesting. I found the same percentage reduction in 
> translating C++ code to D.

I wonder what the main reasons are for the reduction? I did make 
my D version of the sqlite3 lib slightly better by removing some 
redundancies, but that had only a ~100 line effect on the size 
difference. I know that the basic design is pretty much the same, 
so there's no radical design change that would account for the 
difference.

It could be that I did a better job in subtle ways when 
converting over from C++ because of the experience gained from 
the original work, for example I think the error detection and 
reporting I have in the D version is much simpler, and likely 
accounts for some of the size difference. The question though, is 
could I have implemented the same changes in the C++ version just 
as easily? I'm not so sure about that because when I program in 
D, it "feels" better in terms of being much less tedious to work 
with, so there must be more going on than just a few design 
choices. I also find that I get into these "ah ha" moments, where 
I realize that I don't have to do much of anything extra to make 
something new work - hard to explain without real examples, but I 
know I run into these when working with D more so than when 
working with C++.

An interesting test would be to translate a D program into a C++ 
one, to see if the C++ version will shrink due to subtle 
improvements, but I think that would be very difficult to do if 
there are templates involved. You just cannot make heavy use out 
of templates in C++ like you can in D.

Have you ever translated from D to C++?

--rt