METHOD(| <RKF> | <EUL> | <RK4> |);It is used in a type C node to set the integration method of the differential equations in the node. If RKF is used, the method will be a Runge Kutta method of fourth order with a fifth order calculation to estimate the error (Runge Kutta Fehlberg). The integration path is changed according to the error. If RK4 is used, the method will be a Runge Kutta of fourth order. If EUL is used, the method will be the simple Euler method of the first order. RKF is the more exact and slower. EUL is the less exact and faster.
EABS and EREL are used with RKF method of integration to change the integration step when the error in one step exceeds, respectively in absolute or relative value, the values of these variables. Default options are EABS = 0.00001 EREL = 0.0001.
This procedure may be used only in C type nodes. If used, it must be put at the beginning of the code.
Example:
Growth (C) :: METHOD(RK4); Size' := K_Growth * (1 - Size / MaxSize) * Size; Quantity' := MaxQuant - K_Incr * Quantity; Biomass := SpGr * Size * Quantity; HeatEffect (C) :: METHOD(EUL); K_Growth' := K_Growth_Max - Ctg(Temp) * K_Growth; K_Incr' := K_Incr_Max - Cti(Temp) * K_Incr;It is supposed that K_Growth and K_Incr growth very slowly with Temp so that a less exact but more fast integration method may be used.