I am trying to use three credit pricing engines: IsdaCdsEngine, MidPointCdsEngine and IntegralCdsEngine but I am getting different NPV results from each of them. The case is like this: When I have as an input same cds spread values for different tenors, the npv values are different while when cds spread values differ for different tenors the npv result is similar(still not the same).
I would really appreciate if someone would give me an explanation how do these three engines differ from each other.
