Re: Calculator problem on ARM board

[Nicolas Pitre <nico@xxxxxxx>]

On Wed, 5 Nov 2008, kartikay Malhotra wrote:

> Hello All,
> 
> I am facing a problem. I have a calculator application, which has 14 bit
> screen. When I add two numbers, number1 += number2, where both number1 and
> number2 are double, and one of the numbers is very large, and the other
> number is small, I get an error in result.
> 
> For example, 10000000000000 + 1 gives 1e+13, instead of 10000000000001. This
> is because the result string  is actually 10000000000000.99.
> 
> Is there a problem in the compiler, or is double precision arithmetic
> incorrect? The same application complied for x86 gives no error.

What is your compiler version?

I wrote this little test code:

#include <stdio.h>
#include <stdlib.h>
int main(int argc, char*argv[])
{
        double a = strtod(argv[1], NULL);
        double b = strtod(argv[2], NULL);
        printf("%f + %f = %f\n", a, b, a + b);
        return 0;
}

And here's the result I obtain:

$ double_add_test 10000000000000 1
10000000000000.000000 + 1.000000 = 10000000000001.000000

This is with gcc 4.1.2 configured for an EABI environment using 
soft-float.


Nicolas

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