program to find largest double...

Robert G. Brown rgb at
Fri Apr 20 07:28:31 PDT 2001

Dear Listvolken,

Just for the heck of it, I wrote a little program to evaluate the
largest double precision number that isn't "infinite" on a box.  It uses
ISOC99 calls to test for "infinity" (I tried using signals on an FPE but
it is too painful and not easy to understand anyway).

It seems to work, and tells me that the largest float on my PIII is:

  Biggest double that isn't infinite: 8.9884656743115795e+307

I require 1079 loop passes in a binary search that could probably be
shortened considerably with a little log-scale forethought.

I attach the source tarball (it's small) for the person who (long ago)
wanted this.


Robert G. Brown	             
Duke University Dept. of Physics, Box 90305
Durham, N.C. 27708-0305
Phone: 1-919-660-2567  Fax: 919-660-2525     email:rgb at

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