what is the problem when running the code 2 times?

when i run my code i get the results(for example values of snr and mse), but when i run second time the same code and without changing any thing i get another results with the difference of 1,.. or 0.5 and so on. what is the problem?

[Star Strider]

We have no idea.

We cannot run it at all!

[Kaushik Lakshminarasimhan]

Try clear all before running the code.

[Jan]

Maybe a rand() inside the code? Or is it a script and you forgot to initialize a variable? How could we know without seeing the code?