[SI-LIST] Re: Getting Hspice to accept numbers with mantissa's larger than 8 characters
- From: "Muranyi, Arpad" <arpad.muranyi@xxxxxxxxx>
- To: <si-list@xxxxxxxxxxxxx>
- Date: Wed, 5 Apr 2006 09:37:52 -0700
Taha,
As far as I know they changed to double precision in the nineties,
but this would be best answered by a Synopsys representative...
However, regarding the validity of your question, I wonder what
is the value of having that many digits as input to an iterative
solver where the solutions are inherently not exact? A lot will
depend on the tolerance settings, but even then, the solutions=20
will never be exact.
Once I wanted to generate a zero output and wrote circuit with a
resistor in parallel with a zero volt voltage source, and printed
its current. The numbers were anything but an exact zero.
Add to this the problem of converting floating point decimal
numbers to binary and back, which is what almost all computers
do for us since most of them use binary floating point units.
(There are decimal floating point units too which do not suffer
from these problems).
Depending on the precision you use (single, double, etc) sooner
or later you will start getting digits that make no sense for
even the simplest calculations. For example, I tried 10/3 in
one programming tool. Using single precision, I got:
3.333333253860473600000000000000E+0 and with double precision:
3.333333333333333500000000000000E+0.
We know that neither of these two are correct. Depending on which
programming software you use, some times an even more basic
calculation such as 10.0/1.0 (in not integer representation)
will not result in 10.000000000000000000000000.
So what are you trying to achieve with so many digits?
Arpad Muranyi
Intel Corporation
-----------------------------------------------------------------
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] =
On Behalf Of Taha Amiralli
Sent: Wednesday, April 05, 2006 6:37 AM
To: Fred Balistreri
Cc: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: Getting Hspice to accept numbers with mantissa's =
larger than 8 characters
Thanks for the reply Fred,
I have looked up the option that you had recommeneded (i.e. NUMDGT)
and the hspice manual mentions that this option is used to specify the
"Number of significant digits to print, for output variable values."
My concern is more along the lines of inputs since, from what I
understand, hspice uses single precesion floating point
representations for input values and hence, it only accepts 6-7 digts
of a mantissa.
Sincerely,
-------------------
Taha Amiralli
thamiral [A] uwo [D] ca
thamiral [A] gmail [D] com
MESc Candidate 2007, Computer Engineering
The University Of Western Ontario
BESc, BSc. 2005,
Computer Engineering & Computer Science
The University Of Western Ontario
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