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From: ghh@mpq.mpg.de To: gcc-gnats@gcc.gnu.org Subject: optimization/5017: i386 floating point optimization Date: Wed, 05 Dec 2001 04:46:00 -0000 [thread overview] Message-ID: <200112051238.fB5Cc4W25044@lp27.amp.uni-hannover.de> (raw) >Number: 5017 >Category: optimization >Synopsis: i386 floating point optimization >Confidential: no >Severity: serious >Priority: medium >Responsible: unassigned >State: open >Class: wrong-code >Submitter-Id: net >Arrival-Date: Wed Dec 05 04:46:00 PST 2001 >Closed-Date: >Last-Modified: >Originator: Gerhard Heinzel >Release: 3.0.2 >Organization: Albert Einstein Institut Hannover, Germany >Environment: System: Linux lp27 2.4.4-4GB #1 Wed May 16 00:37:55 GMT 2001 i686 unknown Architecture: i686 host: i686-pc-linux-gnu build: i686-pc-linux-gnu target: i686-pc-linux-gnu configured with: ../configure >Description: The included small test program fails when compiled with gcc -O3 -o mybes mybes.c -lm It works with -O0. indication of failure is the following output. The first line starting with "5.00" is garbage. There should not be any "nan" 4.00 18 4.0944813915730677499e-11 11.301921952136330496 4.00 19 4.3099804121821765789e-12 11.301921952136330496 4.00 20 4.3099804121821765788e-13 11.301921952136330496 4.00 21 4.1047432496973110274e-14 11.301921952136330496 4.00 22 3.7315847724521009341e-15 11.301921952136330496 4 11.301921952136330773 6.62406158447265625 5.00 1 nan 1 5.00 2 nan nan 5.00 3 nan nan 5.00 4 nan nan 5.00 5 nan nan >How-To-Repeat: #include <stdio.h> double mybesi0 (double x) { int k = 0; long double sum = 0; long double add = 1; long double x2 = x / 2.; if (x == 0) return 1; if (x < 0) x = -x; if (x > 50) { fprintf (stderr, "argument to mybesi0 too large:%g\n", x); exit (1); } add = 1; for (;;) { sum += add * add; add /= (++k); add *= x2; printf("%4.2f %3d %30.20Lg %30.20Lg\n",x,k,add,sum); if (add / sum < 1e-15) break; } return sum; } float bessi0 (float x) { float ax, ans; double y; if ((ax = fabs (x)) < 3.75) { y = x / 3.75; y *= y; ans = 1.0 + y * (3.5156229 + y * (3.0899424 + y * (1.2067492 + y * (0.2659732 + y * (0.360768e-1 + y * 0.45813e-2))))); } else { y = 3.75 / ax; ans = (exp (ax) / sqrt (ax)) * (0.39894228 + y * (0.1328592e-1 + y * (0.225319e-2 + y * (-0.157565e-2 + y * (0.916281e-2 + y * (-0.2057706e-1 + y * (0.2635537e-1 + y * (-0.1647633e-1 + y * 0.392377e-2)))))))); } return ans; } void main (void) { double x; for (x = 0; x <= 50; x += 1) printf ("%.20g %.20g %.20g\n", x, mybesi0 (x), bessi0(x)); } >Fix: >Release-Note: >Audit-Trail: >Unformatted:
next reply other threads:[~2001-12-05 12:46 UTC|newest] Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top 2001-12-05 4:46 ghh [this message] 2001-12-05 20:14 rodrigc 2001-12-05 20:16 rodrigc
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