A computer-implemented method evaluates credit exposure of a portfolio of financial instruments. A deal object is established for each instrument. The deal object comprises a representation of the instrument and a valuation function for representing how the value of the instrument is related to underlying market variables. Risk factor model are established with each model representing a market variable which may affect the value of the instruments. A deal parabolic function is established representing each deal object valuation function by operation of the deal object valuation function on each risk factor model to which it is sensitive. The coefficients of each deal parabolic function established at a same instant from the deal objects represented in the portfolio are summed in order to build a portfolio parabolic function approximating the overall portfolio value for that instant.