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</o:shapelayout></xml><![endif]--></head><body lang=EN-US link=blue vlink=purple><div class=WordSection1><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif";color:#1F497D'>Title: RFE: 64 bit pointers needed<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif";color:#1F497D'>Author: Justin Senseney<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif";color:#1F497D'>Organization: National Institutes of Health<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif";color:#1F497D'>Owner: Justin Senseney<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif";color:#1F497D'>Created: 2012/04/17<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif";color:#1F497D'>Type: Feature<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif";color:#1F497D'>State: Draft<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif";color:#1F497D'>Exposure: Open<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif";color:#1F497D'>Component: core/lang<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif";color:#1F497D'>Scope: JDK<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif";color:#1F497D'>JSR: TBD<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif";color:#1F497D'>RFE: 4963452 (4850923, 4880587, 4088441, 6292967)<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif";color:#1F497D'>Discussion: compiler-dev@openjdk.java.net<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif";color:#1F497D'>Start: 2012/Q3<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif";color:#1F497D'>Depends: <o:p></o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif";color:#1F497D'>Blocks: <o:p></o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif";color:#1F497D'>Effort: XL<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif";color:#1F497D'>Duration: L<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif";color:#1F497D'>Template: 1.0<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif";color:#1F497D'>Internal-refs: <o:p></o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif";color:#1F497D'>Reviewed-by: <o:p></o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif";color:#1F497D'>Endorsed-by: <o:p></o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif";color:#1F497D'>Funded-by: <o:p></o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif";color:#1F497D'>Summary<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif";color:#1F497D'>-------<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif";color:#1F497D'>As per the Java Language Specification, section 10.4, all array access in Java is done by using an int as index. Since an int is a signed 32bit value, this limits the total number of addressable elements of an array to 2**31 (about 2 billion). It should be possible to address an array using 64bit values.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif";color:#1F497D'>Goals<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif";color:#1F497D'>-----<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif";color:#1F497D'>Improved handling of large datasets that need to be stored in contiguous arrays.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif";color:#1F497D'>Non-Goals<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif";color:#1F497D'>---------<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif";color:#1F497D'>Not changing existing range of Integer<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif";color:#1F497D'>Success Metrics<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif";color:#1F497D'>---------------<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif";color:#1F497D'>Able to compile boolean[] a = new boolean[Long.MAX_VALUE]; <o:p></o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif";color:#1F497D'>Motivation<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif";color:#1F497D'>----------<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif";color:#1F497D'>While having access to 2 billion entries may seem sufficient, there are very compelling performance reasons to be able to use more in a single array. As an example, consider a square n*n matrix, stored as an array (either row or column major, doesn't matter which). Since an array stores at most 2**31 entries, this means that n=sqrt(2**31)=46341, thus the matrix cannot be very large. For multidimensional arrays this is an even more severe limitation (3d Tensors could at most be of size 1290).<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif";color:#1F497D'>Description<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif";color:#1F497D'>-----------<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif";color:#1F497D'>The scope of this work is extensive, however the solution may be quite technically feasible.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif";color:#1F497D'>Alternatives<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif";color:#1F497D'>------------<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif";color:#1F497D'>A workaround is to use an array of arrays (ie. double[][]). However there is no guarantee that successive rows will be laid of linearly in memory, and therefore performance may be severely penalized. Experimentally, performance may suffer by a factor of over 2, often far greater.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif";color:#1F497D'>Also, most existing matrix packages (ie. LAPACK) assumes linear storage, and are thus incompatible with a double[][] storage (requires double[]). Calling a LAPACK routine with a jagged storage thus requires extra array copying and memory allocation, and can further decrease performance and increase memory requirements.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif";color:#1F497D'>Testing<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif";color:#1F497D'>-------<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif";color:#1F497D'>It should be possible to address arrays using 64bit integers (long?), as this provides a seamless transition for users of 64bit computers. <o:p></o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif";color:#1F497D'>Risks and Assumptions<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif";color:#1F497D'>---------------------<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif";color:#1F497D'>Use of array of array constructs (use double[][] instead of double[]) possible as workaround. This feature is well implemented in C/C++ without any problem, so should be quite technically feasible to implement.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif";color:#1F497D'>Dependences<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif";color:#1F497D'>-----------<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif";color:#1F497D'>None none.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif";color:#1F497D'>Impact<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif";color:#1F497D'>------<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif";color:#1F497D'>My group has requested this feature for several years. It is currently listed as one of the top 25 RFEs on http://bugs.sun.com/top25_rfes.do. Please help Java maintain its relevance by implementing this. I have several image processing applications that are severely limited by this bug, these images cannot be opened in most Java applications. These include electron microscopy and micro-CT images where storage of a single slice requires more entries than allowable in a Java array.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif";color:#1F497D'>Thank you for considering this RFE,<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif";color:#1F497D'>Justin Senseney<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif";color:#1F497D'>BIRSS/ISL/DCB/CIT/NIH<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif";color:#1F497D'>301-594-5887<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif";color:#1F497D'>301-480-0028 (fax)<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif";color:#1F497D'>Building 12A/2015<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif"'><a href="http://mipav.cit.nih.gov">http://mipav.cit.nih.gov</a><o:p></o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif"'><a href="http://dcb.cit.nih.gov/~senseneyj">http://dcb.cit.nih.gov/~senseneyj</a><o:p></o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif"'><a href="http://image.nih.gov">http://image.nih.gov</a><o:p></o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif";color:#1F497D'><o:p> </o:p></span></p></div></body></html>