Hello, why is it that when running the while, the last value is not the same as when defining the value of L, for example I tried directly for a value of L 1.5 and it gives me 2.44, but if I run with the while that same curve gives 2,633, the strange thing is that the same number of curves appears as programmed in the while, I can't see what the error could be.

Try this: • the reset must be placed after the alterparam command • To ensure the last iteration is performed (L=1.5) set

stop_l=1.5001

to get rid of numerical errros while incrementing

l_act

Why should that 0.0001 have to be specified? is it an ngspice bug?

no, it's not a ngspice bug. The same will probably happen in a C program. In floating point arithmetic if you add many times 0.05 to a floating point number there are rounding errors. Never check for a==b if a and b are floating point numbers and one of the two is the result of a calculation. Test this C program:

#include <stdio.h>

int main(int argc, char *argv[])
{
  double start_l = 1.0;
  double stop_l = 1.5;
  double delta_l = 0.05;
  double act_l = start_l;

  while( act_l <= stop_l) {
    printf("act_l = %g\n", act_l);
    act_l += delta_l;
  }
  return 0;
}

the output is:

schippes@asus:~$ ./test
act_l = 1
act_l = 1.05
act_l = 1.1
act_l = 1.15
act_l = 1.2
act_l = 1.25
act_l = 1.3
act_l = 1.35
act_l = 1.4
act_l = 1.45

You see the last iteration is not performed because the last

w_act

is not exactly 1.5 since adding 0,05 many times produces rounding errors. There is no exact representation of 0.05 in binary:

0,05 (dec)  = 0.000011001100110011001100110011001100110011....(bin)

I understand, that is what it is about, that is, that while is working as while(i<10) and not as (i<=10)

add a small value to the

stop_l

and you will be ok.

thanks