There is a piece of code confuse me, which runs in windows! Here is the code:
#define point_float2uint(x) *((unsigned int *)&x)
float divide_1000(float y)
{
float v = y / 1000.0f;
return v;
}
float divide_1000(int y)
{
float v = float(y) / 1000.0f;
return v;
}
void float_test(void)
{
int num[5] = {67975500, 67251500, 67540620, 69435500, 70171500};
for (int i = 0; i < 5; ++i)
{
int a = num[i];
float af_f = divide_1000(float(a));
float af_i = divide_1000((a));
printf("src num:%d, af_f:%f, %x, af_i:%f, %x\n", num[i], af_f, point_float2uint(af_f), af_i, point_float2uint(af_i));
}
}
Here is the output, compiled by vs2005:
src num:67975500, af_f:67975.507813, 4784c3c1, af_i:67975.500000, 4784c3c0
src num:67251500, af_f:67251.507813, 478359c1, af_i:67251.500000, 478359c0
src num:67540620, af_f:67540.625000, 4783ea50, af_i:67540.617188, 4783ea4f
src num:69435500, af_f:69435.507813, 47879dc1, af_i:69435.500000, 47879dc0
src num:70171500, af_f:70171.507813, 47890dc1, af_i:70171.500000, 47890dc0
The question is: why I use the "divide_1000", get the different result in windows? This is not what I want! And I find that not all the integer result in different, but some just like the code above.
Here is the the output, comipled by gcc4.4.5 in debian:
src num:67975500, af_f:67975.507812, 4784c3c1, af_i:67975.507812, 4784c3c1
src num:67251500, af_f:67251.507812, 478359c1, af_i:67251.507812, 478359c1
src num:67540620, af_f:67540.625000, 4783ea50, af_i:67540.625000, 4783ea50
src num:69435500, af_f:69435.507812, 47879dc1, af_i:69435.507812, 47879dc1
src num:70171500, af_f:70171.507812, 47890dc1, af_i:70171.507812, 47890dc1
I get the same result in useing different function "divide_1000". That's what I want.