From: <keith.briggs@bt.com>
To: <gsl-discuss@sourceware.org>
Subject: RE: Not clear to understand :)
Date: Thu, 22 Nov 2007 11:40:00 -0000 [thread overview]
Message-ID: <6546343904687E41B19D8E5A26AB9F530175DA0C@E03MVB2-UKBR.domain1.systemhost.net> (raw)
In-Reply-To: <1195731261.5477.14.camel@localhost.localdomain>
These are *not* equivalent in floating point, of course. The first is better.
Even better:
for (i = 1; i <= n; i++)
{
m_x += (x[i * xstride] - m_x) / i;
m_y += (y[i * ystride] - m_y) / i;
}
Keith
-----Original Message-----
From: gsl-discuss-owner@sourceware.org
[mailto:gsl-discuss-owner@sourceware.org]On Behalf Of Serhiy Lisovenko
Sent: 22 November 2007 11:34
To: gsl-discuss@sourceware.org
Subject: Not clear to understand :)
in file fit/linear.c
for (i = 0; i < n; i++)
{
m_x += (x[i * xstride] - m_x) / (i + 1.0);
m_y += (y[i * ystride] - m_y) / (i + 1.0);
}
and other same...
code equivalent to
for (i = 0; i < n; i++)
{
m_x +=x[i * xstride];
m_y +=y[i * ystride];
}
m_x/=(double)n;
m_y/=(double)n;
But the second code is more clear and some faster (no extra divisions).
next prev parent reply other threads:[~2007-11-22 11:40 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-11-22 11:33 Serhiy Lisovenko
2007-11-22 11:40 ` keith.briggs [this message]
2007-11-22 16:13 ` Patrick Alken
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