Most efficient way to find the greatest of three ints

How about

return i > j? (i > k? i: k): (j > k? j: k);

two comparisons, no use of transient temporary stack variables...

To find the greatest you need to look at exactly 3 ints, no more no less. You're looking at 6 with 3 compares. You should be able to do it in 3 and 2 compares.

int ret = max(i,j);
ret = max(ret, k);
return ret;

Pseudocode:

result = i
if j > result:
  result = j
if k > result:
  result = k
return result