From: "David C. Hoos, Sr." <david.c.hoos.sr@ada95.com>
Subject: Re: Calculating SQRT in ADA
Date: 1999/03/25
Date: 1999-03-25T00:00:00+00:00 [thread overview]
Message-ID: <gGUJY5yd#GA.202@pet.hiwaay.net> (raw)
In-Reply-To: 7dei9a$dvo$1@nnrp1.dejanews.com
Mark A Biggar wrote in message <36FAA3DF.42C31CF@lmco.com>...
>Hans Marqvardsen wrote:
>>
>> John Herro wrote:
>
>No,no,no,no!
>
>This algorithm has quadratic convergence. This means that each time
through the
>loop doubles the number of correct bits in the answer. So with IEEE double
>precession float you need loop at most 6 times, and even with extended
float
>7 times, so don't test against a torerance at all, just loop 6 or 7 times
>and be done with it.
>
No,no,no,no! (to coin a phrase)
The number of correct bits doubles with every iteration, only if you are
counting place holding bits as well as mantissa bits. So,
if you take the square root of 2.0e100, for example, 173 iterations are
required if the argument is used as the initial estimate.
similar number is required for 0.5e-100, but only six iterations are
required for 2.0e00 or 0.5e00.
This is why as Robert stated first, and I reiterated in my earlier post, the
coice of the initial estimate is very important, if
you're concerned about execution time.
If the machine representation is known, an improved initial estimate can be
made using the halving the exponent method I outlined
in my earlier post.
next prev parent reply other threads:[~1999-03-25 0:00 UTC|newest]
Thread overview: 55+ messages / expand[flat|nested] mbox.gz Atom feed top
1999-03-24 0:00 Calculating SQRT in ADA cmcrae
1999-03-23 0:00 ` Chris Morgan
1999-03-24 0:00 ` Marin David Condic
[not found] ` <36F913E0.75F51763@lmco.com>
1999-03-24 0:00 ` John Herro
1999-03-24 0:00 ` Hans Marqvardsen
[not found] ` <36FAA3DF.42C31CF@lmco.com>
1999-03-26 0:00 ` Tom Moran
1999-03-25 0:00 ` robert_dewar
1999-03-25 0:00 ` robert_dewar
1999-03-25 0:00 ` John Herro
1999-03-24 0:00 ` Hans Marqvardsen
1999-03-25 0:00 ` David C. Hoos, Sr.
1999-03-25 0:00 ` robert_dewar
1999-03-25 0:00 ` David C. Hoos, Sr. [this message]
1999-03-26 0:00 ` Howard W. LUDWIG
1999-03-26 0:00 ` Ole-Hjalmar Kristensen
1999-03-27 0:00 ` robert_dewar
1999-03-29 0:00 ` Robert I. Eachus
1999-03-30 0:00 ` robert_dewar
1999-04-02 0:00 ` Robert I. Eachus
1999-03-30 0:00 ` robert_dewar
1999-04-02 0:00 ` Robert I. Eachus
1999-04-03 0:00 ` robert_dewar
1999-03-25 0:00 ` robert_dewar
1999-03-26 0:00 ` Calculating SQRT in Ada John Herro
1999-03-26 0:00 ` David C. Hoos, Sr.
1999-03-26 0:00 ` John Herro
1999-03-24 0:00 ` Ada 83 - Sometimes still chosen Richard D Riehle
1999-03-25 0:00 ` robert_dewar
1999-03-25 0:00 ` Richard D Riehle
1999-03-25 0:00 ` Marin David Condic
1999-03-26 0:00 ` robert_dewar
1999-03-25 0:00 ` robert_dewar
1999-03-25 0:00 ` Richard D Riehle
1999-03-25 0:00 ` Larry Kilgallen
1999-03-26 0:00 ` robert_dewar
1999-03-26 0:00 ` Richard D Riehle
1999-03-26 0:00 ` Tom Moran
1999-03-26 0:00 ` Larry Kilgallen
1999-03-29 0:00 ` Marin David Condic
1999-03-29 0:00 ` Tarjei Tj�stheim Jensen
1999-03-27 0:00 ` Matthew Heaney
1999-03-26 0:00 ` Tom Moran
1999-03-26 0:00 ` Tarjei Tj�stheim Jensen
1999-03-27 0:00 ` robert_dewar
1999-03-27 0:00 ` Tarjei Tj�stheim Jensen
1999-03-25 0:00 ` Calculating SQRT in ADA robert_dewar
1999-03-24 0:00 ` Howard W. LUDWIG
1999-03-25 0:00 ` Larry Kilgallen
1999-03-24 0:00 ` bob
1999-03-24 0:00 ` Niklas Holsti
1999-03-26 0:00 ` als0045
1999-03-26 0:00 ` als0045
1999-03-26 0:00 ` bob
1999-03-26 0:00 ` Marin David Condic
1999-03-26 0:00 ` David C. Hoos, Sr.
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