Changeset 1029 for docs/PACT2011


Ignore:
Timestamp:
Mar 25, 2011, 7:15:50 PM (8 years ago)
Author:
lindanl
Message:

section 7

Location:
docs/PACT2011
Files:
2 edited

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  • docs/PACT2011/07-avx.tex

    r1004 r1029  
    105105benefits of the reduced SIMD instruction count are achieved only
    106106in the AVX 128-bit version.  In this case, the benefits of 3-operand
    107 form seem to fully translate to performance benefits.   Bizarrely,
    108 perhaps, the performance of Parabix2 in the 256-bit AVX implementation
     107form seem to fully translate to performance benefits. 
     108Based on the reduction of overall Bitwise-SIMD instructions we expected a 11\% improvement in performance.
     109Instead, perhaps bizzarely the performance of Parabix2 in the 256-bit AVX implementation
    109110does not improve significantly and actually degrades for files with
    110 higher markup density.  We believe that this is primarily due to
    111 the current AVX implemention in Sandy Bridge, with significant
    112 latency in many of the 256-bit instructions in comparison to their
    113 128-bit counterparts.   If these latency issues can be addressed
    114 in future AVX implementations, further substantial performance
    115 and energy benefits could be realized in XML parsing with Parabix2
     111higher markup density (average 10\%). Dew.xml, on which Bitwise-SIMD instructions reduced by 39\%, we saw a performance improvement of 8\%.
     112We believe that this is primarily due to the intricacies of the first generation AVX implemention in Sandy Bridge,
     113with significant latency in many of the 256-bit instructions in comparison to their
     114128-bit counterparts. The 256-bit instructions also have different scheduling constraints that seem to reduce overall SIMD throughput.   If these latency issues can be addressed
     115in future AVX implementations, further substantial performance and energy benefits could be realized in XML parsing with Parabix2.
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