Is there anything I can do about it? Install an optimization library? Change some setting? How can difference in floating point arithmetic be explained?
I would not rely on this software for benchmarking on linux. Here is a thread of complaints about the fact that geekbench mysterious profiles 32-bit linux systems faster than 64-bit systems on the same 64-bit hardware.
I suppose it's not inconceivable that that be accurate, but it seems pretty unlikely that gcc -- which compiles all GNU/linux binary distros and is possibly the most widely used compiler in the world -- would be so flawed and yet no one else has said boo about it. Meanwhile the makers of geekbench admit:
We've been able to reproduce the problem you reported. From what we can tell it's a problem with the compiler used to build Geekbench for Linux; the 64-bit code it generates is slower than the 32-bit code it generates. We're looking into ways to work around this issue.
In the meantime if you're not satisfied with Geekbench please let me know and I would be happy to refund your purchase.
They don't say which compiler they used to build geekbench, perhaps because if they did, the claim that "the 64-bit code it generates is slower than the 32-bit code" could be evaluated and investigated. It's certainly a very serious claim and one wonders why they would continue to use that compiler if this is the case.
No doubt geekbench is something that makes it nice and easy to print scores. I'm not sure how well it would score itself, however.