A user-annotated reference implementation identifies variable values generated by the reference implementation during its execution. A software implementation under analysis is executed. Variable values in the running memory of the program code of the software implementation under analysis, during its execution, are identified and copied. The variable values traced from the running memory of the program code are compared against the annotated variable values generated by the reference implementation, to determine a similarity between the program code under analysis, and the reference implementation. An output is generated that is indicative of whether the traced variables from the program code under analysis are the same as the annotated variable values generated by the reference implementation.