Quote Originally Posted by accord99 View Post
Because the WPrime score is given in seconds and where lower is better, you use the inverse of what you are suggesting. Or you can think of it this way, the 2500K does 32M digits in 10.37 seconds, or the equivalent of 3.086 million digits per second. The 2600K does 4.4 million digits per second or 42.6% more work (faster) than the 2500K.
Just to formalize what you two are at:
  • Speedup = Time_Old / Time_New
  • Time = CPI * Instr_in_prog / Clk_freq
    (CPI = cycles per instruction, the inverse of IPC)


Quote Originally Posted by Lanek View Post
A little question about FMA4 and XOP instructions set ( AVX-AMD Intel use FMA3 and not the same AVX ( no XOP )... Can thoses different instruction set have an impact somewhere if the software, or codes, use a specific compiler ( from intel or AMD ).

I think specially on some synthetic benchmarks as SandraSys, where the benchmarks use FMA and AVX instructions, but i think we can count easely see them in "real " appliccations. Otherwise, does the softwares code need be updated or optimised taking in count thoses different instructions set ?
To start from the beginning, additions to the ISA are will most-always require updates to the compiler and hence re-compile of the code. By using an applicable optimizing compiler (like Intel's ICC or AMD's x86 Open64), just compiling with the new instruction MIGHT be enough to exploit the instruction set well enough, heavily depending on how the original code was written.

I'm not quite an expert when it comes to modern compilers and what commonly is necessary for the programmer to prod at... but in the case of FMA4 (and FMA3), the target programs should at least already be written using intrinsics (a way to express SIMD structures to the compiler) and already have the related operations part of the algorithm. This is more applicable to software using image/signal processing methods.

To summarize, compilers that are updated to use (and hopefully optimize) for the new instructions are all that's needed to use them with your code. However, it's usually the case that the code has to be written (from an algorithmic and somewhat syntax perspective) such that the compiler knows what to do.