Changes between Initial Version and Version 1 of Ticket #38766, comment 4


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Timestamp:
Apr 13, 2013, 9:49:27 AM (11 years ago)
Author:
Veence (Vincent)
Comment:

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  • Ticket #38766, comment 4

    initial v1  
    11Hallo!
    22
    3 Clang 3.2 has been released with a bug in the AVX assembler, so if you try to compile it on a recent hardware, it will produce a faulty code. The bug has been fixed early in the clang3.3 stage, so it is a logical choice to use it as a compiler, even though it is only a developement version. If you use clang3.2 or gcc instead, you have to give up using AVX and downgrade to SSE, and you lose 50% bandwidth.
     3Clang 3.2 has been released with a bug in the AVX assembler, so if you try to compile Atlas on a recent hardware, it will produce a faulty code. The bug has been fixed early in the clang3.3 stage, so it is a logical choice to use it as a compiler, even though it is only a developement version. If you use clang3.2 or gcc instead, you have to give up using AVX and downgrade to SSE, and you lose 50% bandwidth.
    44
    55As for the memory use, I’d bet this is not caused directly by Clang, but by the way Atlas probes the machine in order to pick up the best parameters for compilation: it tries every possible combination and then evaluate the resulting code by running it in a loop. By the way, Atlas has precompiled values for gcc47, so it has not to go through this time-consuming phase. However, since clang failed to pass most of the tests up to the 3.3 version, no values are available for it.