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From: "debian-gcc at lists dot debian dot org" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug libgcj/16122] New: gij - Incorrect result due to computations in extended precision on x86 Date: Mon, 21 Jun 2004 19:58:00 -0000 [thread overview] Message-ID: <20040621195829.16122.debian-gcc@lists.debian.org> (raw) [forwarded from http://bugs.debian.org/255525] 3.3.4 release and 3.4.1 branch, bug submitter writes: Concerning the following Java source: ------------------------------------------------------------------ // $Id: test.java 3734 2004-06-21 15:36:52Z lefevre $ public class test { public static void main(String[] args) throws Exception { test t = new test(); t.doTest(); } volatile double x, y, z, d; public void doTest() { x = 9007199254740994.0; /* 2^53 + 2 */ y = 1.0 - 1/65536.0; z = x + y; d = z - x; System.out.println("z = " + z); System.out.println("d = " + d); } } ------------------------------------------------------------------ I've compiled it with "gcj -C test.java" (GCC 3.3.4). Both IBM's and Sun's JVM give the correct result: greux:~/wd/src/fp> /global/greux/lefevre/IBMJava2-131/jre/bin/java test z = 9.007199254740994E15 d = 0.0 greux:~/wd/src/fp> /usr/local/j2re1.4.1/bin/java test z = 9.007199254740994E15 d = 0.0 but not gij: greux:~/wd/src/fp> /usr/bin/gij test z = 9.007199254740996E15 d = 2.0 gij should switch the FPU of the x86 processor (Pentium III in my case) to rounding in double precision to avoid the effect of the "double rounding" (you may find some information about this effect here: <http://www.srware.com/linux_numerics.txt>). -- Summary: gij - Incorrect result due to computations in extended precision on x86 Product: gcc Version: 3.4.1 Status: UNCONFIRMED Severity: normal Priority: P2 Component: libgcj AssignedTo: unassigned at gcc dot gnu dot org ReportedBy: debian-gcc at lists dot debian dot org CC: gcc-bugs at gcc dot gnu dot org,java-prs at gcc dot gnu dot org GCC host triplet: i486-linux http://gcc.gnu.org/bugzilla/show_bug.cgi?id=16122
next reply other threads:[~2004-06-21 19:58 UTC|newest] Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top 2004-06-21 19:58 debian-gcc at lists dot debian dot org [this message] 2004-06-21 20:24 ` [Bug libgcj/16122] " pinskia at gcc dot gnu dot org 2004-06-22 6:04 ` vincent at vinc17 dot org 2004-06-22 6:05 ` vincent at vinc17 dot org 2004-06-22 16:51 ` mckinlay at redhat dot com
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