Hi every body I have a questoin about subject matter. when computation doing and number of iteration increases ,why velocity of computation decreases? for example 5 iterations in start of calculate takes 5 sec. but in iteration from 1000 to 1005 it takes 5 minutes. tanks alot.

it completely depends on the problem that you are trying to solve. if later in the problem, the number of computations that need to be done per iteration increase, obviously time required per iteration will increase.

also if you are using a window machine, check if you are using enough virtual memory.