Re: [Swarm-Modelling] Floating point arithmetic

[Marcus G. Daniels]

Russell Standish wrote:

> I am very *unconvinced* that we need yet another computer language to
> solve the issues. C++ works extremely well in a high performance
> setting, and its curious that it wasn't mentioned in any of those
> articles (only Fortran, which is becoming more C++ like by the year).
>  
I agree that C++ is versatile enough to provide the scalability sought 
by Chapel and Fortress.  Existing commercial OpenMP compilers go a fair 
ways toward that, as do packages POOMA 
(http://savannah.nongnu.org/projects/freepooma).  The question is how 
many people will run screaming in the process.   Both Microsoft and Sun 
apparently felt C++'s user domain was limited, thus we have C# and Java.

The design of these two new languages is motivated by the DARPA HPCS 
initative to improve programmer productivity for scientific and 
engineering applications.  In other words, make it easy to learn a 
modern object-oriented language while still providing crucial control 
over locality and numerics, that, for example, Java lacks. 

Besides control, both languages contribute new functional ideas absent 
in C++.   Fortress offers an object model based on Traits 
(http://www.cse.ogi.edu/~black/publications/TR_CSE_02-012.pdf) and 
Chapel introduces structural abstractions and operators on them from the 
ZPL language 
(http://www.cs.washington.edu/research/zpl/papers/papers.html).  For 
example, in ZPL, one can declare that an array is sparse, and the 
compiler will encode and traverse it appropriately. 

In terms of transparency to scientific users, Fortress facilitates 
direct use of mathematical notion in programs.  This talk 
(http://research.sun.com/sunlabsday/docs/Talks/Track1/1.02_steele.pdf) 
has a variety of examples of that.

To me, the appeal of both languages is the emphasis is on performance 
and full exploitation of logical concurrency.   Both companies have 
novel multithreading products (Cray's MTA and Sun's Niagara/Rock), so 
one can expect these companies to be motivated to implement these 
languages and make them work well in the horizon of the 2007-2010 HPCS 
delivery date.  
Cray, IBM, and Sun's contracts are each about $50 million US.

Here are some slides on IBM's project, and its language called X10.
http://www.research.ibm.com/vee04/Sarkar.pdf