[fpc-pascal] fast sqrt routine
Pianoman
pianoman at centrum.sk
Sat Mar 11 13:44:52 CET 2006
Hi, I need to perform very fast squareroot (sqrt) operations on double type
nukmbers.
I tried this
function mysqrt(a:double):double;
var y,yn:double;
begin
yn:=a;
repeat
y:=yn;
yn:=(y*y+a)/(2*y);
until abs(yn-y) < 10e-16;
mysqrt:=yn;
end;
but it is quite slow (FPC uses Heron iterations) which is 10 times faster
than this code but I need even faster sqrt routin.
Any ideas for optimizing the function written above would be appreciated.
Pianoman
----- Original Message -----
From: <fpc-pascal-request at lists.freepascal.org>
To: <fpc-pascal at lists.freepascal.org>
Sent: Saturday, March 11, 2006 12:00 PM
Subject: fpc-pascal Digest, Vol 19, Issue 17
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> Today's Topics:
>
> 1. problem setting up serial port (Marc Santhoff)
> 2. Re: problem setting up serial port (Sebastian G?nther)
> 3. Re: problem setting up serial port (Michael Van Canneyt)
> 4. Re: problem setting up serial port (Marc Santhoff)
> 5. Re: problem setting up serial port (Marc Santhoff)
> 6. makeskel --update (Vincent Snijders)
> 7. Re: makeskel --update (Michael Van Canneyt)
> 8. Re: problem setting up serial port (Marc Santhoff)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Fri, 10 Mar 2006 15:51:46 +0100
> From: Marc Santhoff <M.Santhoff at t-online.de>
> Subject: [fpc-pascal] problem setting up serial port
> To: FPC-Pascal users discussions <fpc-pascal at lists.freepascal.org>
> Message-ID: <1142002306.316.7.camel at localhost.das.netz>
> Content-Type: text/plain
>
> Hi,
>
> I'm trying to use a serial port at 1200baud, 7N2 with this code
> sequence:
>
> <snip>
> fCom := fpOpen('/dev/cuaa0', O_RDWR OR O_NOCTTY );//OR O_NONBLOCK);
> if (fCom < 0) then begin
> writeln(stderr, 'Couldn''t open serial port.');
> halt(1);
> end;
>
> r := 0;
> fillchar(tios, sizeof(tios), #0);
>
> cfsetispeed(tios, B1200);
> cfsetospeed(tios, B1200);
>
> tios.c_cflag := CREAD or CLOCAL or CS7 or CSTOPB;
> tios.c_oflag := 0;
> tios.c_iflag := IGNBRK OR IGNPAR;
> tios.c_lflag := 0;
> r := tcsetattr(fCom, TCSANOW, tios);
> if (r = -1) then begin
> writeln(stderr, 'tcsetattr failed!');
> fpClose(fCom);
> halt(1);
> end;
> </snip>
>
> and all I get when running it is: 'tcsetattr failed!'. The rights are
> okay and running as root does make no difference. The hardware is
> working, connections are checked okay ... another program doing mostly
> the same is working as it should.
>
> Maybe I have looked at it for too long, where is the problem?
>
> TIA,
> Marc
>
>
>
> ------------------------------
>
> Message: 2
> Date: Fri, 10 Mar 2006 16:46:06 +0100
> From: Sebastian G?nther <sguenther at gmx.de>
> Subject: Re: [fpc-pascal] problem setting up serial port
> To: FPC-Pascal users discussions <fpc-pascal at lists.freepascal.org>
> Message-ID: <44119F3E.10704 at gmx.de>
> Content-Type: text/plain; charset=ISO-8859-15; format=flowed
>
> Marc Santhoff schrieb:
> >
> > Maybe I have looked at it for too long, where is the problem?
>
> just by the way, there is a unit called 'serial' in Free Pascal. Perhaps
> you might want to use this one, or at least have a look at the source
> code...
>
>
> Regards,
> Sebastian
>
> ------------------------------
>
> Message: 3
> Date: Fri, 10 Mar 2006 17:06:37 +0100 (Romance Standard Time)
> From: Michael Van Canneyt <michael at freepascal.org>
> Subject: Re: [fpc-pascal] problem setting up serial port
> To: FPC-Pascal users discussions <fpc-pascal at lists.freepascal.org>
> Message-ID: <Pine.WNT.4.63.0603101705390.2448 at gru.wisa.be>
> Content-Type: text/plain; charset="iso-8859-1"
>
>
>
> On Fri, 10 Mar 2006, Sebastian Günther wrote:
>
> > Marc Santhoff schrieb:
> >>
> >> Maybe I have looked at it for too long, where is the problem?
> >
> > just by the way, there is a unit called 'serial' in Free Pascal. Perhaps
you
> > might want to use this one, or at least have a look at the source
code...
>
> Better yet, the german Magazine Toolbox distributes a unit by Rainer
> Reush, with a 'TSerial' component.
> AFAIK: Cross-platform and cross-delphi-lazarus...
>
> Michael.
>
> ------------------------------
>
> Message: 4
> Date: Fri, 10 Mar 2006 17:11:32 +0100
> From: Marc Santhoff <M.Santhoff at t-online.de>
> Subject: Re: [fpc-pascal] problem setting up serial port
> To: fpc-pascal at lists.freepascal.org
> Message-ID: <1142007093.316.13.camel at localhost.das.netz>
> Content-Type: text/plain; charset=ISO-8859-15
>
> Am Freitag, den 10.03.2006, 16:46 +0100 schrieb Sebastian Günther:
> > Marc Santhoff schrieb:
> > >
> > > Maybe I have looked at it for too long, where is the problem?
> >
> > just by the way, there is a unit called 'serial' in Free Pascal. Perhaps
> > you might want to use this one, or at least have a look at the source
> > code...
>
> Yes, I know and used it at first, but since it does not give result
> codes back I had to rip it up to create a test program for detecting why
> it doesn't work.
>
> Thank you anyways,
> Marc
>
>
>
> ------------------------------
>
> Message: 5
> Date: Fri, 10 Mar 2006 21:01:46 +0100
> From: Marc Santhoff <M.Santhoff at t-online.de>
> Subject: Re: [fpc-pascal] problem setting up serial port
> To: fpc-pascal at lists.freepascal.org
> Message-ID: <1142020906.316.19.camel at localhost.das.netz>
> Content-Type: text/plain; charset=ISO-8859-15
>
> Am Freitag, den 10.03.2006, 17:06 +0100 schrieb Michael Van Canneyt:
> >
> > On Fri, 10 Mar 2006, Sebastian Günther wrote:
> >
> > > Marc Santhoff schrieb:
> > >>
> > >> Maybe I have looked at it for too long, where is the problem?
> > >
> > > just by the way, there is a unit called 'serial' in Free Pascal.
Perhaps you
> > > might want to use this one, or at least have a look at the source
code...
> >
> > Better yet, the german Magazine Toolbox distributes a unit by Rainer
> > Reush, with a 'TSerial' component.
> > AFAIK: Cross-platform and cross-delphi-lazarus...
>
> Yes, but it is not open source, I'd need something under BSD or LGPL
> style licence.
>
> And my code should work ... ;)
>
> Marc
>
>
>
> ------------------------------
>
> Message: 6
> Date: Fri, 10 Mar 2006 22:18:24 +0100
> From: Vincent Snijders <vsnijders at quicknet.nl>
> Subject: [fpc-pascal] makeskel --update
> To: FPC-Pascal users discussions <fpc-pascal at lists.freepascal.org>
> Message-ID: <4411ED20.9090004 at quicknet.nl>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>
> Hi,
>
> If I use the makeskel --update parameter, what is the best way to merge
> the resulting file to the existing file?
>
> Vincent
>
> ------------------------------
>
> Message: 7
> Date: Fri, 10 Mar 2006 22:50:20 +0100 (Romance Standard Time)
> From: Michael Van Canneyt <michael at freepascal.org>
> Subject: Re: [fpc-pascal] makeskel --update
> To: FPC-Pascal users discussions <fpc-pascal at lists.freepascal.org>
> Message-ID: <Pine.WNT.4.58.0603102250040.1376 at home-office>
> Content-Type: TEXT/PLAIN; charset=US-ASCII
>
>
>
> On Fri, 10 Mar 2006, Vincent Snijders wrote:
>
> > Hi,
> >
> > If I use the makeskel --update parameter, what is the best way to merge
> > the resulting file to the existing file?
>
> Copy and paste.
>
> Michael.
>
> ------------------------------
>
> Message: 8
> Date: Sat, 11 Mar 2006 00:51:52 +0100
> From: Marc Santhoff <M.Santhoff at t-online.de>
> Subject: Re: [fpc-pascal] problem setting up serial port
> To: fpc-pascal at lists.freepascal.org
> Message-ID: <1142034712.316.31.camel at localhost.das.netz>
> Content-Type: text/plain
>
> Hi again,
>
> from trying and decoding error messages I know the call to tcsetattr
> fails with an invalid input. The problem is caused by trying to set the
> field termios.c_ospeed, if left out the call is successfull. So I went
> the way trough the sources and have found something.
>
> On FreeBSD 4.11 termios is defined like this:
>
> /usr/include/termios.h -> sys/termios.h
>
> struct termios {
> tcflag_t c_iflag; /* input flags */
> tcflag_t c_oflag; /* output flags */
> tcflag_t c_cflag; /* control flags */
> tcflag_t c_lflag; /* local flags */
> cc_t c_cc[NCCS]; /* control chars */
> speed_t c_ispeed; /* input speed */
> speed_t c_ospeed; /* output speed */
> };
>
>
> The fpc source file "" defines it as:
>
> <fpc-2.0.2>/share/src/fpc-2.0.2/rtl/freebsd/termios.inc
>
> type
> Termios = packed record
> c_iflag,
> c_oflag,
> c_cflag,
> c_lflag : longint;
> c_line : char;
> c_cc : array[0..NCCS-1] of byte;
> {$IFDEF BSD}
> c_ispeed,
> c_ospeed : longint;
> {$endif}
> end;
> TTermios=Termios;
>
> Note the line in pascal saying "c_line: char" which is missing in the
> systems declaration. This is an error, insn't it?
>
> Marc
>
>
>
> ------------------------------
>
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