Probably because you're using 0 through 3 as the arguments to fesetround(), rather than the proper #defined values:
(e.g. on my Mac, from fenv.h) #define FE_TONEAREST 0x0000 #define FE_DOWNWARD 0x0400 #define FE_UPWARD 0x0800 #define FE_TOWARDZERO 0x0c00 You should use the defines. Glen. On Feb 6, 2014, at 1:18 PM, Bruno Kim Medeiros Cesar <brunokim...@gmail.com> wrote: > Also, I've made a test for this function for all float values in C: > https://gist.github.com/brunokim/8843039 > > Unfortunetely it doesn't work in my system, as it does not have other > rounding modes available besides the default. If anyone suceeds in running > it, please report. > > On Thursday, February 6, 2014 10:07:40 AM UTC-2, Bruno Kim Medeiros Cesar > wrote: > Just to add a bit to the thread: the Java compiler treats java.lang.Math > differently when more efficient alternatives are available. StrictMath is > used only as a fallback. > > From the java.lang.Math javadoc: > By default many of the Math methods simply call the equivalent method in > StrictMath for their implementation. Code generators are encouraged to use > platform-specific native libraries or microprocessor instructions, where > available, to provide higher-performance implementations of Math methods. > Such higher-performance implementations still must conform to the > specification for Math. > > Also, check this StackOverflow question. > > As most probably all your versions use the same native libraries or hardware > instructions, the differences must rely either on float configuration > parameters, like rounding modes, or the order of operations. > > On Wednesday, February 5, 2014 1:58:45 PM UTC-2, Glen Fraser wrote: > Thanks for the tip. After reading your comment, I looked and discovered the > Java library called StrictMath, and tried it (replacing Math/cos and Math/sin > by the StrictMath versions). I did indeed get different results than with > the regular library, but unfortunately still not the same answer as in other > languages. I guess the Java implementation(s) are indeed different. It's > not a big deal for me, just something I found confusing, wondering if I'd > done something wrong. > > Thanks, > Glen. > > On Wednesday, February 5, 2014 4:06:31 PM UTC+1, Jon Harrop wrote: > > IIRC, Java provides unusual trigonometric functions which, I'm guessing, > Clojure is using. I think the Java ones are actually more accurate (and > slower) so you may well find the answer obtained on the JVM is more precise > than the others. > > > Cheers, > > Jon. > > > From: clo...@googlegroups.com [mailto:clo...@googlegroups.com] On Behalf Of > Glen Fraser > Sent: 05 February 2014 13:17 > To: clo...@googlegroups.com > Subject: Confused by Clojure floating-point differences (compared to other > languages) > > > (sorry if you received an earlier mail from me that was half-formed, I hit > send by accident) > > > Hi there, I'm quite new to Clojure, and was trying to do some very simple > benchmarking with other languages. I was surprised by the floating-point > results I got, which differed (for the same calculation, using doubles) > compared to the other languages I tried (including C++, SuperCollider, Lua, > Python). > > > My benchmark iteratively runs a function 100M times: g(x) <-- sin(2.3x) + > cos(3.7x), starting with x of 0. > > > 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. Note that if you only run the function for > about ~110 iterations, you get the same answer in Clojure (or very close), > but then it diverges. > > > I assume my confusion is due to my ignorance of Clojure and/or Java's math > library. I don't think I'm using 32-bit floats or the "BigDecimal" type (I > even explicitly converted to double, but got the same results, and if I > evaluate the type it tells me java.lang.Double, which seems right). Maybe > Clojure's answer is "better", but I do find it strange that it's different. > Can someone explain this to me? > > > Here are some results: > > > Clojure: ~23 seconds > > (defn g [x] (+ (Math/sin (* 2.3 x)) (Math/cos (* 3.7 x)))) > > (loop [i 100000000 x 0] (if (pos? i) (recur (dec i) (g x)) x)) > > ;; final x: 0.24788989279493556 (???) > > > C++ (g++ -O2): ~4 seconds > > double g(double x) { > > return std::sin(2.3*x) + std::cos(3.7*x); > > } > > int main() { > > double x = 0; > > for (int i = 0; i < 100000000; ++i) { > > x = g(x); > > } > > std::cout << "final x: " << x << std::endl; > > return 0; > > } > > // final x: 0.0541718 > > > Lua: ~39 seconds > > g = function(x) > > return math.sin(2.3*x) + math.cos(3.7*x) > > end > > > x = 0; for i = 1, 100000000 do x = g(x) end > > -- Final x: 0.054171801051906 > > > Python: ~72 seconds > > def g(x): > > return math.sin(2.3*x) + math.cos(3.7*x) > > > x = 0 > > for i in xrange(100000000): > > x = g(x) > > > # Final x: 0.05417180105190572 > > > SClang: ~26 seconds > > g = { |x| sin(2.3*x) + cos(3.7*x) }; > > f = { |x| 100000000.do{ x = g.(x) }; x}; > > bench{ f.(0).postln }; > > // final x: 0.054171801051906 (same as C++, Lua, Python; different from > Clojure) > > > Thanks, > > Glen. > > > -- > You received this message because you are subscribed to the Google > Groups "Clojure" group. > To post to this group, send email to clo...@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+u...@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+u...@googlegroups.com. > For more options, visit https://groups.google.com/groups/opt_out. > > > -- > 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 a topic in the Google > Groups "Clojure" group. > To unsubscribe from this topic, visit > https://groups.google.com/d/topic/clojure/kFNxGrRPf2k/unsubscribe. > To unsubscribe from this group and all its topics, send an email to > clojure+unsubscr...@googlegroups.com. > For more options, visit https://groups.google.com/groups/opt_out. -- You received this message because you are subscribed to the Google Groups "Clojure" group. 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