accessing GMP, MPFR, was Re: generating C or Java,

On 2/10/2011 5:02 AM, Leo T Butler wrote:
...

>
> Jon Wilkening at Berkeley has written a nice C++ wrapper around GMP,
> so that the code can look quite natural unlike C code using GMP.
>
> http://math.berkeley.edu/~wilken/code/gmpfrxx/
>
...

This might be useful, but I will mention once again, the possibility of 
just using lisp.
Loading in the generic arithmetic package  (which could be loaded into 
Maxima,
though not the GCL/Windows version),  and loading the appropriate mpfr.dll ,
one can do this in Lisp...

(use-package :mpfr)

(set-prec 100)
(setf r (into 1/3))
                      3.3333333333333333333333333333346^-1  ; I've 
indented the output

(+ r r r)
                     1.
  (sin r)
                    3.2719469679615224417334408526792^-1  ; yes, sine, 
etc   is there.

etc.

That is, the "wrapping" is done rather completely.  The cost of calling
mpfr from lisp is a small percentage of the cost of the mpfr calculation
itself.

If there is considerable "other" code written in Java or C, then this is
not a good idea.  If, however, most of the code is being "automatically
generated" then this might be quite feasible.  In case you haven't
encountered it, Lisp has features like
(loop for i from 1 to n do (print (* i i))

and arrays etc.  Though the array referencing and setting code looks like

(setf (aref b i)  (+ (aref c j)(aref c k)))

this can be easily covered over by writing a few macros;  if everything
is properly declared, it should be not much different from Fortran or C
in speed.

I'm not saying this would be trivial for you to do; I don't know enough
about your calculation and your environment, and obviously you'd
need to learn more about lisps and find a suitable one for your
setup.

I'm guessing you really want bigfloats  (MPFR),  but if you want
integers (GMP) , that's written out, too, since the lisp I was using
has its own different bignum integer package.  Some lisps already use GMP
and you need to do nothing special to access them.


RJF