some basic questions
Dr. Ing. Carlos López
clv2clv at adinet.com.uy
Thu Dec 21 17:17:56 CET 2006
Chris Saunders wrote:
> Hi Carlos
> I am not a GMP expert but I am a programmer who uses GMP.
> As to your first question GMP has three number types integer, real and
> rational each of these types has its own separate representation in memory.
> Each of these types can consume as much memory as the particular computer
> use will allow.
Well... it is not obvious to me the relationship between available memory
and the way a number is represented.
To clarify a little bit: I am looking for something like "... a GMP real
is represented with a mantissa of NMANT bits and an exponent of NEXP bits,
being NMANT user defined, and NEXP defined at compile time..."
> I am not certain of the answer to the second question but I believe the
> answer is no.
OK, but how to estimate a reliable tolerance given the (yet unknown to me)
user defined parameters?
> For the third question the answer is that the more memory your computer
> then the largest floating point number can be larger.
This might be true or not, depending on the way they are represented. To
say something, the largest representable double precision number is unrelated
with the available memory. Another thing is the largest total number of double
precision number which might fit into memory.
I might agree that the above looks confusing: I am looking for the Overflow
Level (largest finite and positive representable number), the Underflow level
(i.e. smallest positive, non zero representable number), etc. all of them
as functions of the (yet unkown to me) user defined parameters (like NMANT,
> I hope this is clear enough and helpful.
> Chris Saunders
> -----Original Message-----
> From: gmp-discuss-bounces at swox.com [mailto:gmp-discuss-bounces at swox.com]
> Behalf Of Dr. Ing. Carlos López
> Sent: Thursday, December 21, 2006 8:16 AM
> To: gmp-discuss at swox.com
> Subject: Some basic questions
> Hello everybody:
> I would like to know if there is a place where to find some basic
> about GMP. By "basic" I meant non-programmer info, but general one.
> I am looking for:
> .- How a number is represented in GMP
> .- Is there something equivalent to the machine epsilon in GMP? If not,
> may I estimate a "tolerance" from the parameters which define the GMP
> .- Which is the largest representable floating point? An the underflow
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