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Re: Solving the Floating-Point Goldilocks Problem!

Cross-posted to 2 groups.

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On 9/2/2011 6:44 AM, jmfbahciv wrote:
> Andy "Krazy" Glew wrote:
>> On 9/1/2011 6:39 AM, jmfbahciv wrote:
>>> 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).
>>
>> Seems that you guys may be pulling my leg.
>
> [puzzled emoticon here]  No.  The PDP-10 had LDB, DPB, ILDB, IDPB.
> I could specify the size of the byte, use the all the hardware
> addressing calculation, which included indexing, indirection.
> The limitation was that a byte had a maximum of 36 bits which
> was the width of a word.  How young are you?  I ask because you
> may not know defintions of word and other terms.
>
> Oh, shit.  I've noticed these posts have been going to comp.arch.
> My apologies.  I'll stop after this one.
>
> /BAH

No, please, I have been enjoying it.

comp.arch is about generic "is this a good idea".

alt.folklore.computers is about "what was done on such and such a machine".

There is a lot of overlap.

comp.arcj is not really interested in the grotty details of which 
version of MVS had which feature.  But is interested in the features.




I thought that you might be pulling my leg because I am often accused of 
pushing for CISCy instructions - and you were pushing my comfort zone.




If you were serious:


What applications made you want these features?

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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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