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Re: Solving the Floating-Point Goldilocks Problem!

Cross-posted to 2 groups.

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Peter Flass wrote:
> On 8/31/2011 12:38 PM, Terje Mathisen wrote:
>> Andy "Krazy" Glew wrote:
>>> On 8/31/2011 1:39 AM, Terje Mathisen wrote:
>>>> As you know LRB have two opcodes for this, to do 1:1:1:1:1 and
>>>> 2:1:2:1:2:1 interleaving.
>>>>
>>>> With this much hw support it becomes most practical to keep the (x,y,z)
>>>> indices separate and merge them before use.
>>>
>>> You are missing one of the other uses of bit-interleaved formats:
>>> They provide scalability.
>>>
>>> Both in online (serial) arithmetic, and in network distribution.
>>>
>>> E.g. you may want to send bit interleaved data with N bits per component
>>> around the network. At the points where you realize that this data is
>>> only ever going to be displayed on a small screen whose viewport you
>>> already know, you start truncating the bitstream.
>>
>> OK, that only works if your world coordinates are big endian, in
>> something like a 0.0 to 1.0 range: In that case you can stop the
>> transmission as soon as you have sent enough bits for the local
>> resolution, i.e. a 640x480 screen would need the top 19 bits or so (you
>> probably need some wiggle room for fractional pixel coords).
>>>
>>> People used to build graphics devices that sent data around like this,
>>> bit serially.
>>
>> With unknown (to the sender) local resolution?
>>>
>>> We may do so again.
>>>
>>> (One of my pet peeves is people assuming, for a non-lossy
>>> transformation, that A->B is necessary, but B->A is not necessary. There
>>> may not be a business case for making the reverse transformation fast.
>>> But nearly always this is a short sighted optimization.)
>>
>> So you desire unpack opcodes as well, something that can quickly extract
>> every second or every third bit?
>>
>
> This is something that would be useful for a lot of things, but should
> be general-purpose.  (thanks to DEC for PDP-10) have source and
> destination pointers in registers, with byte address, bit index and
> number of bits to extract, and increment in bits.  Extract, e.g. an
> arbitrary bit field from the source and store it at an arbitrary bit
> position in the destination.  Then update the pointers, so you could REP
> it, or have a repeat counter.  If I had a nickle for every time I've
> wanted such an instruction...
>
Don't forget the indirect addressing (not to be confused with indexing).

/BAH

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Re: Solving the Floating-Point Goldilocks Problem! jmfbahciv <See.above@aol.com> - 2011-09-01 13:39 +0000
  Re: Solving the Floating-Point Goldilocks Problem! "Andy \"Krazy\" Glew" <andy@SPAM.comp-arch.net> - 2011-09-01 08:18 -0700
    Re: Solving the Floating-Point Goldilocks Problem! jmfbahciv <See.above@aol.com> - 2011-09-02 13:44 +0000
      Re: Solving the Floating-Point Goldilocks Problem! "Andy \"Krazy\" Glew" <andy@SPAM.comp-arch.net> - 2011-09-02 09:37 -0700
        Re: Solving the Floating-Point Goldilocks Problem! Patrick Scheible <kkt@zipcon.net> - 2011-09-02 10:21 -0700
          Re: Solving the Floating-Point Goldilocks Problem! rpw3@rpw3.org (Rob Warnock) - 2011-09-05 06:11 -0500
        Re: Solving the Floating-Point Goldilocks Problem! jmfbahciv <See.above@aol.com> - 2011-09-03 14:57 +0000
          Re: Solving the Floating-Point Goldilocks Problem! Peter Flass <Peter_Flass@Yahoo.com> - 2011-09-03 13:13 -0400
            Re: Solving the Floating-Point Goldilocks Problem! rpw3@rpw3.org (Rob Warnock) - 2011-09-05 06:41 -0500
              Re: Solving the Floating-Point Goldilocks Problem! Peter Flass <Peter_Flass@Yahoo.com> - 2011-09-05 08:21 -0400
              Re: Solving the Floating-Point Goldilocks Problem! jmfbahciv <See.above@aol.com> - 2011-09-05 13:26 +0000
            Re: Solving the Floating-Point Goldilocks Problem! Patrick Scheible <kkt@zipcon.net> - 2011-09-05 22:48 -0700
              Re: Solving the Floating-Point Goldilocks Problem! Quadibloc <jsavard@ecn.ab.ca> - 2011-09-06 16:51 -0700
                Re: Solving the Floating-Point Goldilocks Problem! Morten Reistad <first@last.name> - 2011-09-07 14:14 +0200
                Re: Solving the Floating-Point Goldilocks Problem! Patrick Scheible <kkt@zipcon.net> - 2011-09-07 09:45 -0700
                Re: Solving the Floating-Point Goldilocks Problem! Rob Doyle <radioengr@gmail.com> - 2011-09-07 18:54 -0700
                Re: Solving the Floating-Point Goldilocks Problem! Quadibloc <jsavard@ecn.ab.ca> - 2011-09-08 00:53 -0700
                Re: Solving the Floating-Point Goldilocks Problem! MitchAlsup <MitchAlsup@aol.com> - 2011-09-08 08:00 -0700

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