Date: Sat, 14 May 2016 18:33:09 -0700 From: Conrad Meyer <cem@FreeBSD.org> To: Adrian Chadd <adrian@freebsd.org> Cc: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: Re: svn commit: r299751 - head/sys/dev/bwn Message-ID: <CAG6CVpXZgaykWX54nUnp2UVPqGj=fnS0sMc9adAdT1FH8rZEhw@mail.gmail.com> In-Reply-To: <201605141952.u4EJq4jP017501@repo.freebsd.org> References: <201605141952.u4EJq4jP017501@repo.freebsd.org>
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On Sat, May 14, 2016 at 12:52 PM, Adrian Chadd <adrian@freebsd.org> wrote: > Author: adrian > Date: Sat May 14 19:52:04 2016 > New Revision: 299751 > URL: https://svnweb.freebsd.org/changeset/base/299751 > > Log: > [bwn] migrate sqrt and add another couple of util routines. > > ... > > +unsigned int > +bwn_sqrt(struct bwn_mac *mac, unsigned int x) > +{ > + /* Table holding (10 * sqrt(x)) for x between 1 and 256. */ > + static uint8_t sqrt_table[256] = { > + 10, 14, 17, 20, 22, 24, 26, 28, > ... > + }; > + > + if (x == 0) > + return (0); > + if (x >= 256) { > + unsigned int tmp; > + > + for (tmp = 0; x >= (2 * tmp) + 1; x -= (2 * tmp++) + 1) > + /* do nothing */ ; > + return (tmp); Does this approximation method have a name? > + } > + return (sqrt_table[x - 1] / 10); Why do we store the table as 10*sqrt() if we're just going to divide every entry by ten? Best, Conrad
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