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* [Bug c++/31179] New: strange behaviour of floor rounding
@ 2007-03-15 1:45 hobiger at nict dot go dot jp
2007-03-15 5:37 ` [Bug middle-end/31179] " pinskia at gcc dot gnu dot org
0 siblings, 1 reply; 3+ messages in thread
From: hobiger at nict dot go dot jp @ 2007-03-15 1:45 UTC (permalink / raw)
To: gcc-bugs
This following small program will show the problem
# report.cpp
#include <cmath>
#include <iostream>
int main(int argc, char* argv[])
{
double A=140.70;
double x=floor((A*100));
std::cout << "Testing: A = " << A << " --> A*100 = " << A*100 << " but
floor(A*100) = " << x << "\n";
double B=140.60;
double y=floor((B*100));
std::cout << "Testing: B = " << B << " --> B*100 = " << B*100 << " but
floor(B*100) = " << y << "\n";
}
The program was compiled simply by "g++ report.cpp -o report."
For all machines available here I obtained
Testing: A = 140.7 --> A*100 = 14070 but floor(A*100) = 14069
Testing: B = 140.6 --> B*100 = 14060 but floor(B*100) = 14060
The latter result is as expected but for A=128.7,129.7,130.7....163.7 floor
rounding gives wrong results. This bug has been verified on several
architectures (PIII,P3, WinXP - Cygwin) and under several versions of gcc/g++
(4.1.1 - on FC6, 4.0.2 - on RH, 3.4.6 -on RH)
Any ideas where this comes frome ???
--
Summary: strange behaviour of floor rounding
Product: gcc
Version: unknown
Status: UNCONFIRMED
Severity: critical
Priority: P3
Component: c++
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: hobiger at nict dot go dot jp
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=31179
^ permalink raw reply [flat|nested] 3+ messages in thread
[parent not found: <bug-31179-4@http.gcc.gnu.org/bugzilla/>]
end of thread, other threads:[~2021-09-12 2:51 UTC | newest]
Thread overview: 3+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2007-03-15 1:45 [Bug c++/31179] New: strange behaviour of floor rounding hobiger at nict dot go dot jp
2007-03-15 5:37 ` [Bug middle-end/31179] " pinskia at gcc dot gnu dot org
[not found] <bug-31179-4@http.gcc.gnu.org/bugzilla/>
2021-09-12 2:51 ` pinskia at gcc dot gnu.org
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