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Allen Millers Software quad precision module

 
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ckatholi



Joined: 23 Mar 2006
Posts: 4

PostPosted: Thu Aug 30, 2012 7:07 am    Post subject: Allen Millers Software quad precision module Reply with quote

I sometimes need quad precision in a few calculations where speed is not
the primary concern. I have found a quad precision module at The Allen Miller
Fortran software site and have given it a try. It seems to work but I wondered if anyone else has tried this or knows of an alternative.

Thank you

Charles
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Malcolm Bibby



Joined: 16 Nov 2009
Posts: 33

PostPosted: Sat Sep 01, 2012 11:03 am    Post subject: Reply with quote

Hi Charles. I assume you mean ALAN Miller. He references double-double and quad-double from a Berkeley site. I have used these for several years and found them very reliable. Which particular package, from Alan Miller's site are you using? He seems to have several depending on which compiler you are using!

Malcolm
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ckatholi



Joined: 23 Mar 2006
Posts: 4

PostPosted: Sat Sep 01, 2012 7:03 pm    Post subject: Alan Miller quad precision Reply with quote

Hi Malcolm,

I have been playing with the version called quad_df.f90 (as opposed to quad.f90) the difference being that the latter seems to assume the 80 bit
8087 register structure while the former does not. I compiled with the
compiler option -O0 and it seems to work fine. His test program compiles
and runs and the results seem reasonable. Sadly, so far I have not figured out a clever way to check the results by printing out the result of a known
computation as a long decimal number. I can think of a number of ways of doing this by hand be looking that the binary representation of the two
double precision pieces and converting to decimal...but I am too lazy. Thus
your experience is encouraging. Any tips will be greatly appreciated.

Charles
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