Arduino calculate prime numbers
I wrote some code to stress test my Arduino. The code below will make your Arduino calculate prime numbers.
long start = 0;
int max_seconds = 30;
long i = 2; // Start at 2
long found = 0; // Number of primes we've found
void setup() {
Serial.begin(115200);
while (!Serial) { }
Serial.println("");
Serial.print("Running prime benchmark for ");
Serial.print(max_seconds);
Serial.println(" seconds...");
start = millis();
}
void loop() {
int prime = is_prime(i); // Check if the number we're on is prime
if (prime == 1) {
found++;
if (found % 2000 == 0) {
Serial.print(".");
}
if (found % 50000 == 0) {
Serial.print("\n");
}
}
int running_seconds = (millis() - start) / 1000;
if (max_seconds > 0 && (running_seconds >= max_seconds)) {
Serial.print("\nFound ");
Serial.print(found);
Serial.print(" primes in ");
Serial.print(max_seconds);
Serial.println(" seconds");
delay(10000);
i = 2;
found = 0;
start = millis();
}
i++;
}
int is_prime(long num) {
// Only have to check for divisible for the sqrt(number)
int upper = sqrt(num);
// Check if the number is evenly divisible (start at 2 going up)
for (long cnum = 2; cnum <= upper; cnum++) {
long mod = num % cnum; // Remainder
if (mod == 0) {
return 0;
} // If the remainer is 0 it's evenly divisible
}
return 1; // If you get this far it's prime
}
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February 28th 2022 - random
Should be 3 times faster
uint32_t start = 1;
uint32_t max_seconds = 10;
uint32_t i = 11; // Start at 11
uint16_t found = 4; // Number of primes we've found, start with 4 as there are 4 primes prior 11
void setup() {
Serial.begin(115200);
while (!Serial) { }
Serial.println("");
Serial.print("Prime benchmark for ");
Serial.print(max_seconds);
Serial.println(" seconds...");
start = millis();
}
void loop() {
is_prime(); // to cancel out all numbers modulo 2 or 3 = 0
i+=2; // Odd + 2 = odd
is_prime();
i+=4; //9%3=0 so 11+2+2 would be %3 = 0 so we add here 4 instead of 2
//we could filter out other Prime dividables as 5,7,... but this woud be a mess here
if (millis() >= (start + ((max_seconds)*1000))) {
Serial.print("nFound ");
Serial.print(found);
Serial.print(" primes in ");
Serial.print(max_seconds);
Serial.println(" seconds");
Serial.print(" searched to ");
Serial.print(i-4);
delay(5000);
i = 11;
found = 4;
start = millis();
}
}
boolean is_prime() { // could be void, but my esp did not like it so here with boolean
// Only have to check for divisible for the sqrt(number)
uint32_t upper = sqrt(i);
// Check if the number is evenly divisible (start at 2 going up)
for (uint32_t cnum = 5; cnum <= upper; cnum+=4) { //Same +2 ... +4 trick as before
if (((i % cnum) == 0)) {
return 0;
}
cnum+=2;
if (((i % cnum) == 0)) {
return 0;
}
}
found++;
//Serial.print(i);
//Serial.print("n");
return 1; // If you get this far it's prime
}