This:
long t = millis();
float a = 1.2;
float b = -7.8;
float c;
float d = 0;
for(long i = 0; i < 1000000; i++)
{
c = a + b;
c = c - a;
c = a*c;
c = c/a;
d += c;
}
t = millis()-t;
Serial.print("Time: ");
Serial.println(t);
runs in 10.1 seconds on a Melzi (RepRap Arduino controller with an ATmega1284P clocked at 16 Mhz), and 1.29 seconds on a Due.
Adrian Bowyer
RepRapPro Ltd