This program illustrates the function calls to mergesort and merge in a multiple recursive implementation. Each single call is displayed in a line, along with the arguments (the start and end indeces of the original array to be sorted in that particular call).

For example, the input array [14,7,3,12,9,11,8,10] will be sorted in the following way: We first call mergesort with array[0..7] (ie the whole array). Within this call, mergesort is called again ms(0;3) with array[0..3] and so on. After the ms(0;3) exits, the algorithm continues with array[4..7], which is displayed at the same level as ms(0;3). The numbers on the left denote the depth of the function call in the stack, which equals one for ms(0;3), ms(4,7) and merge(0;3;7).

0: ms(0;7)
1:    ms(0;3)
2:          ms(0;1)
3:              ms(0;0)
3:              ms(1;1)
3:              m(0;0;1)
2:          ms(2;3)
3:              ms(2;2)
3:              ms(3;3)
3:              m(2;2;3)
2:          m(0;1;3)
1:    ms(4;7)
2:          ms(4;5)
3:              ms(4;4)
3:              ms(5;5)
3:              m(4;4;5)
2:          ms(6;7)
3:              ms(6;6)
3:              ms(7;7)
3:              m(6;6;7)
2:          m(4;5;7)
1:    m(0;3;7)