Efficient mixed use of BigInteger and int ?

Question

I need to calculate a cost, which can be arbitrary large. To calculate this cost,
I need to do very small steps, each small step has a cost within [1,10000].
Is it a good idea to use the following strategy. Are there any better ones ?
BigInteger calculateCost() {
1__ BigInteger totalCost = BigInteger.ZERO;
2__ int smallCost = 0;
3__ while(model.step()) { //keep on stepping until done
4_____ smallCost += model.getStepCost();
5_____ if ((smallCost & 0x40000000) > 0) { //look if second bit is set
6________ totalCost = totalCost.add(BigInteger.valueOf(smallCost));
7________ smallCost = 0;
8_____ }
9__ }
10_ totalCost = totalCost.add(BigInteger.valueOf(smallCost));
11_ return totalCost;
jpwinne

Answer 1

Well, if it were me coding it, I'd eliminate the
"smallCost" variable and simply add each item to the
BigInteger. I mean, it seems the only reason you're
doing it that way is for performance. But if you're
so concerned about performance, why is the
system/component coded in java in the first place?Just because you are using Java it is not a good reason to ignore performance altogether. For many appliances, the differance between the Java and other languages aint that big as other unchangable overheads comes into play (network congestion, databases, user interaction), but if performance is ignored, this could radically change. The choice of selecting good algorithm is still a very valid consideration, or as I usually told my students in the old days "If you code a sucky bubblesort in C and an efficient quicksort in Java, does that mean Java is faster than C?". Any application that disregards performance adds to the "Java is so slow" image that it honestly does not deserve for most applications.
For "better" alternatives, I would think there is only one, and that is to use a long as remistigri suggested. Not sure thou from the context if this is a viable solution for you, since you will limit yourself to values under Long.MAX_VALUE. Double could also be an alternative, but with the known drawbacks of precision loss.
You peaked my interest on what you are doing to be honest as I yet have not been involved in an application needing the use of BigInteger, if I exclude crypthograph applications.
Regards,
Peter Norell