Infinite loop when decimals are added
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Leonel Sternberg
on 30 Jul 2022
Moved: Walter Roberson
on 22 Jan 2023
I am making a simple program to calculate the number of times a decimal number has to be multiplied (by positive integers) so that the decimal part (mod1) will = 0.
Example of the code:
%Decimal
ro=0.5854;
n=1;
while mod(ro*n,1)~=0
n=n+1;
end
n
In this case the answer is 5000.
I want to be able to change the last digit of the decimal point. But I am having a problem when I make a small change in the program. I get an infinite loop. The changed program is shown below:
%Decimal
ro=0.585+0.0004;
n=1;
while mod(ro*n,1)~=0
n=n+1;
end
n
I can't understand why I get an infinite loop with this small change - the value of ro changed acordingly but I get an infinite "while" loop. Please explain.
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Accepted Answer
Stephen23
on 30 Jul 2022
Moved: Walter Roberson
on 22 Jan 2023
"Please explain"
Different accumulated floating point error combined with an algorithm that does not take into account the behavior of binary floating point numbers. Also note that the values are not the same:
fprintf('%.30f\n', 0.5854, 0.585+0.0004)
Read more about binary floating point numbers:
This is worth reading as well:
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