It is entirely possible that the 68020 etc uses "extended"
precision (using 64 bit fractions instead of 53 bits) for
floating point registers. It would be surprising though if
this explained how answers differed in the last 8 decimal places.
Regarding wiki, I may have missed its recent evolution,
but the idea of an entirely "democratic" encyclopedia in
which anyone can write about anything seems to me to have distinct
disadvantages for readers who want some authoritative
information.
RJF
Camm Maguire wrote:
> Greetings!
>
> James Amundson <amundson@fnal.gov> writes:
>
>
>>On Thu, 2002-09-19 at 11:09, Richard Fateman wrote:
>>
>>
>>>for i:1 thru 60 do print ([i,is (1.0d0=1.0d0+2^(-i))]); double
>>>for i:1 thru 60 do print ([i,is (1.0=1.0+2^(-i))]); single
>>>
>>>for the first one, you should get i=22 for the first true.
>>>for the second one, i=53 should be the first true.
>>>
>>Ah ha. By that test, single precision float are being implemented as
>>doubles by all three of GCL, Clisp and CMUCL under Linux.
>>
>>Camm, what do you get?
>>
>>
>
> Indeed, I get 53 on both. I'm giving Rick Younie's suggestion of
> -ffloat-store a try. Apparently, the m68k can keep more precision for
> doubles than standard IEEE dictates.
>
>
>>>The way I debug lisp functions is first to make sure
>>>the same answer happens when the code is interpreted rather
>>>than compiled. (if not, it is a compiler error!)
>>>Then if they are the same, by using trace. You can
>>>trace the two different versions and see where they
>>>give different answers. Rarely I
>>>insert in the lisp code (break "id") or output statements
>>>like (format t "~% location xx with values ~s ~s " x y)
>>>
>>>Which all brings to mind the possibility that suggestions
>>>like this should be in a FAQ ... How do I debug lisp code
>>>in Maxima.
>>>
>>Yes. Absolutely. CY was going to start a Wiki. What happened to it?
>>(I'll confess that I've never really used a Wiki, but I believe it is
>>supposed to be a more flexible implementation of a FAQ.)
>>
>>
>
> From my lowly perspective as a C person, having a tool with the same
> functionality as gdb for lisp, as is apparently the case as described
> in Dr. Schelter's docs for dbl mode, but which I have been unable to
> reproduce, would be *very* attractive for people new to the language.
>
> Take care,
>
>
>>--Jim
>>
>>
>>
>