SE250:lab-3:tlou006

Q1

Using the code

int main()
{
 int i,j,t0;
 ArrayList alist;
 arraylist_init( &alist );

for( j=0; j<10; j++ ) {
 t0 = clock();
 for( i=0; i<1000000; i++ ) {
  arraylist_push( &alist, 0 );
  }
 printf("time taken : %d\n", clock() - t0);
 arraylist_clear( &alist );
}

 arraylist_clear( &alist );
 return 0;
}

will hopefully give me the time taken to insert the number 0 one million times into the array list.

The loop is repeated 10times to give me an average.

I made the following change to the code

arraylist_push( &alist, i );

this should add a different number one million times into the array list.

My results showed that, apart from random errors, there is no difference in timing between adding the

same number and adding different numbers to the array list.

Q2

First of all I changed the array growth factor from 2.0 to a number lower than 1; eg 0.9

The result was an instant crash of the program. As expected ^___^

Changing the growth factor to 3.0 saw an increase in performance by about 3-4 milliseconds, this must

be because the function to expand the array had to be called less. I expected this performance boost to

increase as the growth factor increased until the calculation was almost instant, when the array only needed

to be expanded once due to the large growth factor.

Q3

I added

printf("time taken : %d for j = %d \n size is %d \n", j, clock() - t0, alist.capacity);

Hopefully this will help me spot the time changes.

Setting ARRAYLIST_MIN_ALLOC to 10000000 (a lot of memory so the array never runs out of space).

The performance was slower by about ~30milliseconds for a loop putting a number into the array one

million times. This was unexpected. I thought it would be slightly faster, as the array would never run

out of space and the growth calculations won't be needed each time.

Maybe it took time to allocate such a large amount of memory to something.

Q4

Added the line

ensure_capacity( &alist, 10000000 );

at the start of the code.

The time now was the same as the previous sections, ie. before ARRAYLIST_MIN_ALLOC was set to 10000000

faster by ~30milliseconds.

Ran out of time :( spent too long reading the code trying to understand

will finish later