Slow performance compared to C++, ideas?

[John Colvin]

On Sunday, 2 June 2013 at 15:53:58 UTC, Roy Obena wrote:
> On Sunday, 2 June 2013 at 14:34:43 UTC, Manu wrote:
>> On 2 June 2013 21:46, Joseph Rushton Wakeling
>
>> Well this is another classic point actually. I've been asked 
>> by my friends
>> at Cambridge to give their code a once-over for them on many 
>> occasions, and
>> while I may not understand exactly what their code does, I can 
>> often spot
>> boat-loads of simple functional errors. Like basic programming 
>> bugs;
>> out-by-ones, pointer logic fails, clear lack of understanding 
>> of floating
>> point, or logical structure that will clearly lead to 
>> incorrect/unexpected
>> edge cases.
>> And it blows my mind that they then run this code on their big 
>> sets of
>> data, write some big analysis/conclusions, and present this 
>> statistical
>> data in some journal somewhere, and are generally accepted as 
>> an authority
>> and taken seriously!
>
> You're making this up. I'm sure they do a lot of data-driven
> tests or simulations that make most errors detectable. They may
> not be savvy programmers, and their programs may not be
> error-free, but boat-loads of errors? C'mon.

I really wish he was making it up. Sadly, he's not.

A lot of HPC scientific code is, at best, horribly fragile.