Thanks, this is a satisfying answer. You're probably right that the other languages are all using the C standard math library (I naïvely assumed Java would too, but I see that's not the case). And yes, as I said, it is a rather contrived (and chaotic) example.
Glen. On Feb 5, 2014, at 6:22 PM, Konrad Hinsen <googlegro...@khinsen.fastmail.net> wrote: > --On 5 Feb 2014 05:17:13 -0800 Glen Fraser <holag...@gmail.com> wrote: > >> My benchmark iteratively runs a function 100M times: g(x) <-- sin(2.3x) + >> cos(3.7x), starting with x of 0. > > A quick look at the series you are computing suggests that it has chaotic > behavior. Another quick looks shows that neither of the two values that > you see after 100M iterations is a fix point. I'd need to do a careful > numerical analysis to be sure, but I suspect that you are computing > a close to random number: any numerical error at some stage is amplified > in the further computation. > > If you get identical results from different languages, this suggests that > they all end up using the same numerical code (probably the C math library). > I suggest you try your Python code under Jython, perhaps > that will reproduce the Clojure result by also relying on the JVM > standard library. > >> In the other languages, I always got the result 0.0541718..., but in >> Clojure I get 0.24788989.... I realize this is a contrived case, but -- >> doing an identical sequence of 64-bit floating-point operations on the >> same machine should give the same answer. > > Unfortunately not. Your reasoning would be true if everyone adopted > IEEE float operations, but in practice nobody does because the main > objective is speed, not predictability. The Intel hardware is close > to IEEE, but not fully compatible, and it offers some parameters that > libraries can play with to get different results from the same operations. > > Konrad. -- You received this message because you are subscribed to the Google Groups "Clojure" group. To post to this group, send email to clojure@googlegroups.com Note that posts from new members are moderated - please be patient with your first post. To unsubscribe from this group, send email to clojure+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/clojure?hl=en --- You received this message because you are subscribed to the Google Groups "Clojure" group. To unsubscribe from this group and stop receiving emails from it, send an email to clojure+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/groups/opt_out.
