Re: Continue with learning C

From	Reinhardt Behm <rbehm@hushmail.com>
Newsgroups	comp.lang.c
Subject	Re: Continue with learning C
Date	2016-09-20 17:59 +0800
Organization	A noiseless patient Spider
Message-ID	<nrr1a0$vkl$3@dont-email.me> (permalink)
References	(12 earlier) <nro66t$nhe$1@dont-email.me> <c2903a40-202c-4296-9f95-6668b4429cd5@googlegroups.com> <nrq3l2$4v2$1@dont-email.me> <b68940ce-9481-43a8-aa11-2ccb15be903e@googlegroups.com> <nrqmpn$6h0$2@dont-email.me>

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AT Tuesday 20 September 2016 15:00, David Brown wrote:

> On 20/09/16 05:47, supercat@casperkitty.com wrote:
>> On Monday, September 19, 2016 at 8:33:39 PM UTC-5, Reinhardt Behm wrote:
>>> AT Monday 19 September 2016 23:04, supercat wrote:
>>>> Energizing the primary brake alone would be acceptable behavior.
>>>> Energizing
>>>> the secondary brake alone would also be acceptable behavior.  A
>>>> majority-vote system, however, would generate an unacceptable behavior
>>>> even though only one controller was malfunctioning.
>>>
>>> Such redundant system only make sense if the software on each system is
>>> developed according to the same requirements. Having clear requirements
>>> should prevent our scenario. With clearly specified behavior there is
>>> not "the other controller thinks ...". If it "thinks" differently it is
>>> either defective or the software was not been developed according to the
>>> requirements.
>> 
>>> Assuming that the software was developed as it should be, why should in
>>> your example the second controller come to a different conclusion about
>>> the state and usability of the primary brake? It has the same
>>> information about the brakes since it gets the same inputs. The software
>>> was developed to the same requirements so it has to come to the
>>> conclusions. There is - and may not - no random element in there. The
>>> only reason for such differences is a malfunction, either hardware or
>>> software.
>> 
>> If the programs were developed independently, floating-point rounding
>> might
>> not match precisely.  If the decision about which brake to use is a
>> sufficiently close call, a rounding difference could make the difference
>> between selecting one brake vs the other.
>> 
> 
> To a large extent, you avoid floating point precisely because it can be
> hard to get bit-perfect.  But if you /do/ need floating point, you can
> do so by being very careful to track the possible effects of rounding
> errors in order to avoid getting different results.

There is just a difference between real engineering and experimental 
programming. ;-)

-- 
Reinhardt

Thread

Continue with learning C Alla _ <modelling.data@gmail.com> - 2016-09-15 05:11 -0700
  Re: Continue with learning C "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2016-09-15 05:29 -0700
  Re: Continue with learning C Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-09-15 15:01 +0100
  Re: Continue with learning C Richard Heathfield <rjh@cpax.org.uk> - 2016-09-15 15:32 +0100
    Re: Continue with learning C Alla _ <modelling.data@gmail.com> - 2016-09-15 08:10 -0700
    Re: Continue with learning C luser droog <luser.droog@gmail.com> - 2016-09-15 12:06 -0700
      Re: Continue with learning C Richard Heathfield <rjh@cpax.org.uk> - 2016-09-15 21:38 +0100
        Re: Continue with learning C Malcolm McLean <malcolm.mclean5@btinternet.com> - 2016-09-16 21:02 -0700
          Re: Continue with learning C "Osmium" <r124c4u102@comcast.net> - 2016-09-17 08:03 -0500
          Re: Continue with learning C Richard Heathfield <rjh@cpax.org.uk> - 2016-09-17 22:38 +0100
            Re: Continue with learning C "James R. Kuyper" <jameskuyper@verizon.net> - 2016-09-17 18:14 -0400
              Re: Continue with learning C raltbos@xs4all.nl (Richard Bos) - 2016-09-18 10:47 +0000
              Re: Continue with learning C Alla _ <modelling.data@gmail.com> - 2016-09-19 01:25 -0700
                Re: Continue with learning C Ian Collins <ian-news@hotmail.com> - 2016-09-19 20:51 +1200
                Re: Continue with learning C James Kuyper <jameskuyper@verizon.net> - 2016-09-19 09:49 -0400
                Re: Continue with learning C Richard Heathfield <rjh@cpax.org.uk> - 2016-09-19 15:15 +0100
                Re: Continue with learning C Keith Thompson <kst-u@mib.org> - 2016-09-19 11:39 -0700
                Re: Continue with learning C Reinhardt Behm <rbehm@hushmail.com> - 2016-09-20 09:55 +0800
                Re: Continue with learning C David Brown <david.brown@hesbynett.no> - 2016-09-20 08:50 +0200
                Re: Continue with learning C Reinhardt Behm <rbehm@hushmail.com> - 2016-09-20 18:04 +0800
                Re: Continue with learning C David Brown <david.brown@hesbynett.no> - 2016-09-20 13:25 +0200
                Re: Continue with learning C Reinhardt Behm <rbehm@hushmail.com> - 2016-09-20 20:18 +0800
                Re: Continue with learning C David Brown <david.brown@hesbynett.no> - 2016-09-20 15:25 +0200
                Re: Continue with learning C Jerry Stuckle <jstucklex@attglobal.net> - 2016-09-20 08:45 -0400
                Re: Continue with learning C Reinhardt Behm <rbehm@hushmail.com> - 2016-09-20 22:05 +0800
                Re: Continue with learning C Jerry Stuckle <jstucklex@attglobal.net> - 2016-09-20 10:56 -0400
                Re: Continue with learning C Rosario19 <Ros@invalid.invalid> - 2016-09-19 18:55 +0200
                Re: Continue with learning C Anton Shepelev <anton.txt@gmail.com> - 2016-09-25 01:08 +0300
            Re: Continue with learning C Malcolm McLean <malcolm.mclean5@btinternet.com> - 2016-09-17 17:08 -0700
              Re: Continue with learning C Richard Heathfield <rjh@cpax.org.uk> - 2016-09-18 01:11 +0100
                Re: Continue with learning C Jerry Stuckle <jstucklex@attglobal.net> - 2016-09-17 21:32 -0400
                Re: Continue with learning C David Brown <david.brown@hesbynett.no> - 2016-09-18 16:27 +0200
                Re: Continue with learning C Jerry Stuckle <jstucklex@attglobal.net> - 2016-09-18 16:08 -0400
                Re: Continue with learning C Malcolm McLean <malcolm.mclean5@btinternet.com> - 2016-09-18 07:30 -0700
                Re: Continue with learning C Jerry Stuckle <jstucklex@attglobal.net> - 2016-09-18 16:07 -0400
                Re: Continue with learning C David Brown <david.brown@hesbynett.no> - 2016-09-18 16:38 +0200
                Re: Continue with learning C BartC <bc@freeuk.com> - 2016-09-18 16:37 +0100
                Re: Continue with learning C Reinhardt Behm <rbehm@hushmail.com> - 2016-09-18 23:54 +0800
                Re: Continue with learning C Malcolm McLean <malcolm.mclean5@btinternet.com> - 2016-09-18 16:56 -0700
                Re: Continue with learning C Richard Heathfield <rjh@cpax.org.uk> - 2016-09-18 17:05 +0100
                Re: Continue with learning C "James R. Kuyper" <jameskuyper@verizon.net> - 2016-09-18 12:28 -0400
                Re: Continue with learning C Malcolm McLean <malcolm.mclean5@btinternet.com> - 2016-09-18 17:00 -0700
                Re: Continue with learning C Alla _ <modelling.data@gmail.com> - 2016-09-19 01:40 -0700
                Re: Continue with learning C "Osmium" <r124c4u102@comcast.net> - 2016-09-19 08:55 -0500
                Re: Continue with learning C "Osmium" <r124c4u102@comcast.net> - 2016-09-18 11:31 -0500
                Re: Continue with learning C Ian Collins <ian-news@hotmail.com> - 2016-09-19 07:25 +1200
                Re: Continue with learning C Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-09-18 20:36 +0100
                Re: Continue with learning C "James R. Kuyper" <jameskuyper@verizon.net> - 2016-09-18 15:45 -0400
                Re: Continue with learning C Rosario19 <Ros@invalid.invalid> - 2016-09-19 18:58 +0200
                Re: Continue with learning C "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2016-09-18 09:55 -0700
                Re: Continue with learning C "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2016-09-18 10:12 -0700
                Re: Continue with learning C luser droog <luser.droog@gmail.com> - 2016-09-18 13:11 -0700
                Re: Continue with learning C David Brown <david.brown@hesbynett.no> - 2016-09-18 21:54 +0200
                Re: Continue with learning C supercat@casperkitty.com - 2016-09-18 15:58 -0700
                Re: Continue with learning C Richard Heathfield <rjh@cpax.org.uk> - 2016-09-19 07:09 +0100
                Re: Continue with learning C David Brown <david.brown@hesbynett.no> - 2016-09-19 10:04 +0200
                Re: Continue with learning C BartC <bc@freeuk.com> - 2016-09-19 10:38 +0100
                Re: Continue with learning C David Brown <david.brown@hesbynett.no> - 2016-09-19 13:29 +0200
                Re: Continue with learning C supercat@casperkitty.com - 2016-09-19 08:04 -0700
                Re: Continue with learning C Reinhardt Behm <rbehm@hushmail.com> - 2016-09-20 09:33 +0800
                Re: Continue with learning C supercat@casperkitty.com - 2016-09-19 20:47 -0700
                Re: Continue with learning C David Brown <david.brown@hesbynett.no> - 2016-09-20 09:00 +0200
                Re: Continue with learning C Reinhardt Behm <rbehm@hushmail.com> - 2016-09-20 17:59 +0800
                Re: Continue with learning C Ike Naar <ike@iceland.freeshell.org> - 2016-09-20 17:24 +0000
                Re: Continue with learning C David Brown <david.brown@hesbynett.no> - 2016-09-20 08:57 +0200
                Re: Continue with learning C supercat@casperkitty.com - 2016-09-20 10:53 -0700
                Re: Continue with learning C Reinhardt Behm <rbehm@hushmail.com> - 2016-09-19 13:19 +0800
                Re: Continue with learning C Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-09-19 01:30 +0100
      Re: Continue with learning C Alla _ <modelling.data@gmail.com> - 2016-09-19 01:15 -0700
  Re: Continue with learning C Barry Schwarz <schwarzb@dqel.com> - 2016-09-15 12:38 -0700
  Re: Continue with learning C fir <profesor.fir@gmail.com> - 2016-09-21 11:42 -0700
    Re: Continue with learning C fir <profesor.fir@gmail.com> - 2016-09-21 12:40 -0700
      Re: Continue with learning C fir <profesor.fir@gmail.com> - 2016-09-21 12:49 -0700
      Re: Continue with learning C fir <profesor.fir@gmail.com> - 2016-09-23 14:47 -0700
        Re: Continue with learning C fir <profesor.fir@gmail.com> - 2016-09-23 14:59 -0700

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