[PCB_FORUM] Re: Metric to English - English to Metric

  • From: "Austin Franklin" <austin@xxxxxxxxxxxx>
  • To: <icu-pcb-forum@xxxxxxxxxxxxx>
  • Date: Wed, 24 Aug 2005 17:25:48 -0400

Hi Richard,

Perhaps more than a decade ago, the CPU and code speed may have been an
issue.  But, in the realm we are talking about (a printed circuit board and
the range of numbers and precision necessary) IMO and IME the compiler
imposes no significant restrictions, nor does the "math processor" in the
CPU.  Again, it is simply a matter of knowing where the decimal point is.

In Allegro, you don't convert because the tool can not handle it.  In a tool
that can adequately handle it, this is not an issue.

Regards,

Austin

 -----Original Message-----
From: icu-pcb-forum-bounce@xxxxxxxxxxxxx
[mailto:icu-pcb-forum-bounce@xxxxxxxxxxxxx]On Behalf Of richard moffat
Sent: Wednesday, August 24, 2005 5:15 PM
To: icu-pcb-forum@xxxxxxxxxxxxx
Subject: [PCB_FORUM] Re: Metric to English - English to Metric


  Cadence is probably making a compromise for speed.  The way that other
tools may allow a seemless interchange is to have a greater length of
significant numbers in the internal database, especially converting
metric->imperial.

  The programmers are restricted to that they are given:  The C compiler,
and the maths processor on the CPU.

  In short:  don't convert!


  >>> austin@xxxxxxxxxxxx 25/08/2005 9:08:15 a.m. >>>

  Hi,

  > Conversely, 1/10 (0.1) cannot be exactly represented in base 2...

  I design ASICs, and I have done a LOT of arithmetic functions in ASICs,
and
  use decimal points all the time.  All hardware arithmetic functions are
done
  in base 2.  It's simply a matter of knowing where the decimal point is and
  using enough digits.  Yet, it goes on to explain the solution (as I said,
  knowing where the decimal point is)...so I fail to see the *real* problem.

  As was pointed out, PADS has no problem switching back and forth between
the
  two unit systems, so I simply don't believe Allegro can't do it as well.
It
  seems like this may be a self imposed restriction:

  > The real issue is that some numbers can't be represented exactly in the
  > standard floating point representation.

  Why do they have to use "standard" floating point representation anyway?
  Sounds like someone programmed themselves into a corner, and instead
fixing
  it, they are trying to come up with explanations...instead of solutions.
  Sigh.  To me, this is a huge weakness of Allegro.

  Regards,

  Austin

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