The following snippet of code:
IloNum i = 2*0.6 + 3*0.4 + 0.6 - 0.4 + 1 + 0.6 - 0.4 + 1;
IloNum j = 4.8;
cout << "i=" << i << ", j=" << j << ", (i>j)=" << (i > j) << endl;
has the following output:
i=4.8, j=4.8, (i>j)=1
Have I overlooked some details in the documentation or is this a bug?
You should remember that as soon as you do some float operations you have some tiny errors.
If I rewrite your model in OPL
float i = 2*0.6 + 3*0.4 + 0.6 - 0.4 + 1 + 0.6 - 0.4 + 1;
float j = 4.8;
execute
{
writeln("i=" , i , ", j=" ,j ,", (i>j)=" , (i > j) );;
}
float i2=i-4.8;
float j2=j-4.8;
execute
{
writeln("i2=",i2);
writeln("j2=",j2);
}
then I get
i=4.8, j=4.8, (i>j)=true
i2=8.881784197e-16
j2=0
which shows the tiny imprecision that leads to what looks like a paradox
And let me underline that
float i = 2*6 + 3*4 + 6 - 4 + 10 + 6 - 4 + 10;
float j = 48;
execute
{
writeln("i=" , i , ", j=" ,j ,", (i>j)=" , (i > j) );;
}
float i2=i-48;
float j2=j-48;
execute
{
writeln("i2=",i2);
writeln("j2=",j2);
}
gives
i=48, j=48, (i>j)=false
i2=0
j2=0