#include <stdio.h>
#define ITERS 1000000000ul
int main( int argc, char **argv ) {
__int64 start;
int i;
double d;
getch();
start = GetTickCount64();
if( argc > 1 ) {
printf( "%u integer divisions: ", ITERS );
start = GetTickCount64();
for( i = 1; i < ITERS; i++ )
d = 1 / i;
printf( "Took %I64d ticks\n", GetTickCount64() - start );
}
else {
printf( "%u integer multiplications: ", ITERS );
start = GetTickCount64();
for( i = 1; i < ITERS; i++ )
d = 1 * i;
printf( "Took %I64d ticks\n", GetTickCount64() - start );
}
}
And on my 64-bit processor, for 32-bit ints I got: C:\test>muldiv-b 1
1000000000 integer divisions: Took 3432 ticks
C:\test>muldiv-b
1000000000 integer multiplications: Took 2917 ticks
The numbers vary ~+-30 ticks for individual runs, but division is always ~10% slower than multiplication. I put this down the subsequent promotion of the result to a double rather than the opcode itself.
Conversely, if I use 64-bit ints division is almost 7X slower than multiplication: C:\test>muldiv-b
1000000000 integer multiplications: Took 3011 ticks
C:\test>muldiv-b 1
1000000000 integer divisions: Took 20764 ticks
This is think is due to the fact that two 64-bit registers are involved in the result.
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