prog8/examples/bsieve.p8

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%import textio
%import floats
%zeropage basicsafe
%option no_sysinit
; The "Byte Sieve" test. https://en.wikipedia.org/wiki/Byte_Sieve
; Note: this program is compatible with C64 and CX16.
main {
sub start() {
c64.SETTIM(0, 0, 0)
const ubyte ITERS = 10
uword count
uword i
uword prime
uword k
const uword SIZEPL = 8191
uword flags_ptr = memory("flags", SIZEPL, $100)
txt.print("calculating...\n")
repeat ITERS {
sys.memset(flags_ptr, SIZEPL, 1)
count = 0
for i in 0 to SIZEPL-1 {
if @(flags_ptr+i) {
prime = i + i + 3
k = i + prime
while k <= SIZEPL-1 {
@(flags_ptr + k) = false
k += prime
}
; txt.print_uw(prime)
; txt.spc()
count++
}
}
}
txt.print_uw(count)
txt.print(" primes\n")
float time = c64.RDTIM16() / 60.0
floats.print_f(time)
txt.print(" sec total = ")
floats.print_f(time/ITERS)
txt.print(" sec per iteration\n")
}
}