a program , an apparatus and a method verify a program that efficiently verifies a concurrent / parallel program , allowing interactively debugging the current / parallel program . the program causes a computer to execute a detection step that detects the function that has been altered and the function that uses a shared variable influenced by the alteration out of the program to be verified before and after the alteration and also detects the part that is influenced by the alteration , the control structure part and the other parts , a model generation step that generates a model on the basis of the outcome of the detection in the detection step and a verification step that verifies the program to be verified after the alteration by comparing the model of the program to be verified before the alteration and the model of the program to be verified after the alteration .