divRemain(); returns nDivides( / ) and nRemainder( % )

[SixTsevN]

Hey there,
I'm trying to run tests on the speed and efficiency of my function.

It's called divRemain() and it's purpose is to take a dividend, an empty int, a divisor and return the number of divisions and number remainder.

I was querying the performance counter either side of my function and either side of the divide operator ( / ) and the modulus operator ( % ); to compare their speeds. Problem is I kept getting a weird deltaTime from the operators.
Is this because they are too fast to measure?

I just want some feedback on my function and constructive criticism on how to make it better.

Here it is:

void divRemain(int& nDivides, int& nRemain, int divisor)
{
	// Working Variables
	//---------------------------------------------------------
	int       i(0);             // index iterator
	int       counter(0);       // bit counter
	bool      empty(false);     // is-empty trigger
	bitset<2> negative = { 0 }; // negative double trigger

	// IF, dividend is negative:
	if (nDivides < 0)
		negative[0] = 1; // trigger

	// IF, divisor is negative:
	if (divisor < 0)
	{
		negative[1] =  1; // trigger

		divisor    *= -1; // negate
	}

	// Initialise the bitset
	bitset<32> bin(nDivides);

	// Assign zero value to nDivides and nRemain
	//---------------------------------------------------------
	nDivides = 0;
	nRemain  = 0;

	// WHILE, bitset is not empty, LOOP:
	while (!empty)
	{
		// IF, 1's place is set:
		if (bin[0] == 1)
		{
			// add 1 to counter
			counter++; 

			// IF, counter is full:
			if (counter == divisor)
			{
				nDivides++;  // add 1 to nDivides

				counter = 0; // reset counter
			}

			// set 1's place to zero
			bin.set(0, 0); 
		}

		// IF, 1's place is not set:
		if (bin[0] == 0)
		{
			// Search for the next set bit
			//---------------------------------------------------------
			// WHILE, not at last element, LOOP:
			while (i <= 31)
			{
				// IF, found next set bit:
				if (bin[i] == 1)
				{
					// add 1 to counter
					counter++;     

					// IF, counter is full:
					if (counter == divisor)
					{
						nDivides++;  // add 1 to nDivides

						counter = 0; // reset counter
					}

					// unset bit
					bin.set(i, 0); 

					// Record the (bitset - 1)
					//---------------------------------------------------------  
					// WHILE, more than zero, LOOP:
					while (i > 0)
					{
						i--;        // iterate down bitset

						bin.set(i); // set bit
					}

					break;
				}
				// ELSE IF, next set bit not found:
				else if (bin[i] == 0 && i != 31)
				{
					i++; // continue search

					continue;
				}
				// ELSE IF, bitset empty:
				else if (bin[i] == 0 && i == 31)
				{
					empty = true; // trigger

					break;
				}
			}
		}

		// IF, bitset is empty and counter is not zero:
		if (empty && counter != 0)
			nRemain = counter;  // empty counter into nRemainder

		// IF, result is negative and the bitset is empty:
		if (negative.any() && !negative.all() && empty)
		{
			nDivides *= -1; // negate nDivides
			nRemain  *= -1; // negate nRemain
		}
	}
}

Thank you for your time,
SixT

[kbw]

I haven't quite followed the algorithm not can I see your timing points and timer, so I'm not sure, but I I have a could of other comments.

The order of comparison is important. So you should swap the order of these tests as int equality is faster than a bitset lookup in these

else if (bin[i] == 0 && i != 31)

Have you seen div?
http://en.cppreference.com/mwiki/index.php?title=Special%3ASearch&search=div

[SixTsevN]

"The order of comparison is important. So you should swap the order of these tests as int equality is faster than a bitset lookup in these

else if (bin[i] == 0 && i != 31)
"

Thanks, I see what you mean.

//---------------------------------------------------------

I took a look at std::div.

Let me guess, it does exactly what my function does but, better?

Could you show me an example of how to use it?

EDIT:
//---------------------------------------------------------
Nevermind, I looked in the cplusplus.com references:
http://www.cplusplus.com/reference/cstdlib/div/

Thank you for your help.

[kbw]

#include <stdlib.h>
#include <stdio.h>

int main()
{
        div_t d;
        d = div(7, 3);
        printf("7 / 3 = %d remainder %d\n", d.quot, d.rem);

        return 0;
}