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    * YOUR C COMPILER / HARDWARE HAS NON-COMMUTATIVE ARITHMETIC!!!   *
    *                                                                *
    * Your C compiler believes that x*y-y*x can be different from    *
    * zero.  This may be the result of inconsistent rounding in      *
    * your computers hardware when multiply-add instructions are     *
    * used.                                                          *
    *                                                                *
    * On some systems, a Multiply-Add combination whose results are  *
    * different from a Multiply and an Add can cause this to happen. *
    * Results on this system, if it alleges to be IEEE, will differ  *
    * from IEEE systems where arithmetic is commutative.             *
    *                                                                *
    * At least one vendor views this behavior as a feature; if       *
    * commutative arithmetic is important to you, consider using     *
    * compilation options to reduce the amount of optimization or    *
    * eliminate the use of Multiply-Add (this may reduce             *
    * performance but will make it possible to compare computations  *
    * on different systems).                                         *
    *                                                                *
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