change(generatePrimesCPU): Now aborting at half of candidate

Numbers larger than the half of a number are not able to divide a number

main.go

@@ -33,12 +33,18 @@ func printProgress(progress <-chan float32, message string) {
 }
 
 func checkIsDivisibleByPrime(number int64, offset, stride int, primes *[]int64, resultChannel chan bool, ctx context.Context) {
+	threshold := number / 2
 	for i := offset; i < len(*primes); i += stride {
 		select {
 			case <-ctx.Done():
 				resultChannel <- false
 				return
 			default:
+				// no need to continue checking if number is greater than half our number, division is already impossible
+				if (*primes)[i] > threshold {
+					resultChannel <- false
+					return
+				}
 				// only have to check primes, because all other numbers are multiple of primes.
 				// if a number is divisible by a multiple of a prime, it is by definition also divisible by the prime itself.
 				if number % (*primes)[i] == 0 {