i := struct.force.update()

Flags the cycling logic so that a geometry update is performed at the start of the next cycle. Normally this update is performed at the start of cycling, and in large-strain mode at the geometry update interval. Changes to gridpoint mass and gravity caused by density and stiffness changes may not actually affect the calculation unless an update is performed. The return value is ignored.

Note that calling this function every step will slow cycling down, and may in certain cases (most notably cases where the timestep is changing frequently, as in creep) disable checks that prevent instability in a static analysis. Generally it is not necessary to call this more than once every 10 steps at most.

Returns:i - the integer 0