Performance portability

Article: Introduction to OpenCL
By: EduardoS (no.delete@this.spam.com), December 12, 2010 9:04 am
Room: Moderated Discussions
David Kanter (dkanter@realworldtech.com) on 12/11/10 wrote:
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>Yes, but you can't treat them as totally separate. Each set of registers has a
>limited number of ports, so if you only use X registers...you're really screwed.

Your argument invalidates your point... Each lane is a different register set with own ports, in the case there are only one read port per register set and three clocks for reading.

If the programmer use float4 the most obvious think to do is placing each component in a different register set, this is enough to avoid running out of register ports, if instead, the programmer only uses float then the most obvious think to do is to spread over register set to allow more ILP, in fact if the programmer declares float a, b the compilers have more reasons to put them on R1.x and R1.y than on R1.x and R2.x, the statement "To fully utilize teh RF, you need to store 128-bit wide values (for AMD)." doesn't make sense.
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          It is difficult to runtime optimize away the difference between a CPU and GPUMark Roulo2010/12/12 01:20 PM
            It is difficult to runtime optimize away the difference between a CPU and GPUhobold2010/12/12 03:31 PM
              It is difficult to runtime optimize away the difference between a CPU and GPUanon2010/12/12 04:24 PM
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        Specially when the language provides almost no hardware abstraction (NT)EduardoS2010/12/11 10:53 AM
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        Performance portabilityEduardoS2010/12/11 08:23 PM
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    OpenCL - why are there any pointers at all?EduardoS2010/12/16 01:51 PM
      OpenCL - why are there any pointers at all?Rob Thorpe2010/12/17 03:19 AM
        OpenCL - why are there any pointers at all?Richard Cownie2010/12/17 07:02 AM
          OpenCL - why are there any pointers at all?Rob Thorpe2010/12/17 08:29 AM
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              OpenCL - why are there any pointers at all?Rob Thorpe2010/12/17 10:03 AM
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                  OpenCL - why are there any pointers at all?Rob Thorpe2010/12/17 11:19 AM
                    OpenCL - why are there any pointers at all?Richard Cownie2010/12/17 11:51 AM
                OpenCL - why are there any pointers at all?hobold2010/12/17 11:06 AM
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              OpenCL - why are there any pointers at all?Richard Cownie2010/12/18 02:39 PM
  OpenCL article onlineEmil Briggs2010/12/19 06:40 AM
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