Seeking the fastest numerical library for quadruple precision in C/C++/Fortran

[Michael]

Seeking the fastest numerical library for quadruple precision in C/C++/Fortran
Hi all,

I have some computation and simulation which need quadruple precision. I
mean, the double precision is not enough, while high precision such as 1000
digits is not needed, and that's too slow. I guess quadruple precision
exactly fits my problem and should be much faster than double precision.

Could anybody tell me if MS Visual C++, or Intel C, Intel Fortran have
already got quadruple precision in them and they are fully supported on
Intel based cpus? I guess Intel Fortran has quadruple precision, but since I
prefer C/C++ so my first choices are within C/C++ languages.

Moreover, do GSL, Intel MKL, and IMSL etc. have got quadruple precision
support? I only need +, -, *, /, exp, and log.

I eventually have to do everything in C/C++ so I am primarily looking for
numerical libraries, instead of Matlab or Maple or Mathematica's symbolic
capability.

But if you know how to "simulate" quadruple precision in Matlab or Maple, or
Mathematica, in order to see if an algorithm will overslow when converting
into C/C++/Fortran, please let me know. I want to do the algorithm design in
Matlab, and test if it will overflow, before converting everything into
C/C++/Fortran.

If you know how to "simulate" quadruple precision in Matlab, Maple or
Mathematica even with the symbolic toolbox, please let me know too... this
is for algorithm design and testing...

Moreover, are there popular quadruple precision packages? Please recommend
the fastest one. I am really in huge need of speed.

Thank you very much!