Quad Versus 80-bit Arithmetic

[Alan Karp]

I am conducting a survey of those people who need more precision than
provided by IEEE double precision.  I would appreciate any insight you
might have from your PERSONAL experience.  (We've got lots of hearsay
evidence; I want something admissable in court.)

1. Is your need met by a 64-bit mantissa?

2. If you need more than 64 bits in the mantissa, how many more do you
   need?

3. How important is the performance of the extra precision part of
   your code?

4. At what ratio of performance to double precision would you consider
   using higher precision more often - never, only if the performance
   were the same as double precision, 2x slower, 10x slower, up to
   100x slower (e.g., I can't do without it)?

A brief, 100 words or less, summary of your application, why more
precision is needed, and where the extra precision is needed (if not
throughout) would be appreciated.

If I get enough responses, I'll post a summary.