Walking Jun

LSL NSieve Bits Benchmark - Second Life Wiki
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の 篩にビット列を使う方 も試してみました
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若干速い? w
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リストもあげておきます

//

// File: NSieve2.lsl

// Date            Author        number of nodes

// 2008/6/25       walkinglint   68

//

//

// The Great Computer Language Shootout

// http://shootout.alioth.debian.org/

// 

// contributed by Isaac Gouy

// modified by Babbage Linden

//

string hexc = "0123456789ABCDEF";

string setBitArray(integer numbits) {

    string result = "";

    integer i;

    for (i = 0; i < numbits; i += 4) {

        result += "F";

    }

    result += "F";

    return result;

}

string replace(string s, integer index, string char) {

    string result = "";

    if (index >= 1) {

        result += llGetSubString(s, 0, index - 1);

    }

    result += char;

    if (index < (llStringLength(s) - 1)) {

        result += llGetSubString(s, index + 1, -1);

    }

    return result;

}

integer get(string s, integer index) {

    integer charIndex = index / 4;

    integer bitIndex = index % 4;

    integer bits = (integer)("0x" + llGetSubString(s, charIndex, charIndex));

    return bits & (1 << bitIndex);

}

string set(string s, integer index) {

    integer charIndex = index / 4;

    integer bitIndex = index % 4;

    integer bits = (integer)("0x" + llGetSubString(s, charIndex, charIndex));

    bits = bits | (1 << bitIndex);

    return replace(s, charIndex, llGetSubString(hexc, bits, bits));

}

string unset(string s, integer index) {

    integer charIndex = index / 4;

    integer bitIndex = index % 4;

    integer bits = (integer)("0x" + llGetSubString(s, charIndex, charIndex));

    integer mask = 0xF & ~(1 << bitIndex);

    bits = bits & mask;

    return replace(s, charIndex, llGetSubString(hexc, bits, bits));

}

test() {

    integer m = 128;

    string bits = setBitArray(m);

    integer count = 0;

    integer i;

    for (i = 2; i <= m; i++) {

        if (get(bits, i)) {

            integer k;

            for (k = i + i; k <= m; k += i) {

                bits = unset(bits, k);

            }

            count++;

        }

    }

    llSay(0, "Primes up to " + (string)m + " " + (string)count);

}

time() {

    llResetTime();

    llSay(0, "Starting tests...");

    test();

    llSay(0, "Finished tests in " + (string)llGetTime() + "s");

}

default {

    state_entry() {

        time();

    }

    touch_start(integer num) {

        time();

    }

}

あれ? なんで 4? とか思ってしまった...
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0 1 からなる情報をコンパクトに持ちたい時 流用できそうですね w