This invention relates to a method of optimization of a computer program, comprising: a first step (S11, S12, S13, S14) of determination of a call of a function having at least one input parameter, said call corresponding to a first criterion according to which said input parameter is inside an interval substantially smaller than the range of possible values for said input parameter, and to a second criterion corresponding to a desired accuracy for said call; a second step (S2) of automatic generation of an executable code for implementing said function, minimizing execution time for said input parameter being within said interval and compliant with said desired accuracy; a third step (S3) of replacing the existing code implementing said function by the executable code generated at said second step.