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Java Forum / Virtual Machine / May 2006What FPU intructions JDK support
Anyone knows if jdk does support FPU instructions? I'm particularly interested in atan and exp functions.. I've googled around for a time but didn't found anything of specific Thanks Dimitri > Anyone knows if jdk does support FPU instructions? > I'm particularly interested in atan and exp functions.. > I've googled around for a time but didn't found anything of specific Are you asking whether the JVM will actually use certain particular CPU/FPU instructions when executing your code, or are you asking if there exists an API which can perform the equivalent of the above mentioned function, without regards as to what instructions the CPU/FPU will actually execute to implement those functions? - Oliver > Are you asking whether the JVM will actually use certain particular >CPU/FPU instructions when executing your code, or are you asking if there >exists an API which can perform the equivalent of the above mentioned >function, without regards as to what instructions the CPU/FPU will actually >execute to implement those functions? I'm a little drunk but the first that you said, Oliver, >JVM will actually use certain particular >CPU/FPU instructions Thanks, sorry if wasn't clear > I'm a little drunk but the first that you said, Oliver, OK well that's not a question about what the JVM *supports*, it's a question about what the JVM *uses*, isn't it? The answer to that can only be another couple of questions: *which* JVM, *which* CPU? In general, a hint as to the answer is right there in java.lang.Math: '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.' ok, so? how can i know if the jdk 1.6 or 1.5 for linux and windows uses fpu instructions? and which one it uses? I've googled around but I'couldn't find anything clear.. Must I use a debugger to dicover it? Thanks Dimitri Dimitri Ognibene schrieb: > ok, so? > how can i know if the jdk 1.6 or 1.5 for linux and windows uses fpu > instructions? and which one it uses? I've googled around but I'couldn't > find anything clear.. Must I use a debugger to dicover it? The JSE uses StrictMath, which calles native code. So it depends on the JVM implementation what happens. You can download the source of the JVM and look how it's implemented. (Carefully read the licence first.) Timo ok i'll try this, Thanks Dimitri > how can i know if the jdk 1.6 or 1.5 for linux and windows uses fpu > instructions? and which one it uses? I've googled around but I'couldn't > find anything clear.. Must I use a debugger to dicover it? You can probably find out exactly what code is used by using JVMTI, but I've never done that myself, so I can't say how easy or difficult it would be (my guess is that it's pretty tricky). Also, you may find this link relevant: http://blogs.sun.com/roller/page/jag?entry=transcendental_meditation James Gosling writing about the implementation of transcendental functions in Java. -- chris Free MagazinesGet these publications absolutely FREE for up to 12 months. There are no hidden fees and no obligation. Simply choose a title, complete the application form and submit it. Read more ...
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