Wow, it works !
Gw ga ngeh kalo implementasi method toCharArray seperti itu,
& ternyata method charAt langsung akses ke array of char yg jd storage.
Thanks, Kong Putra !
regards,
T Budi S
2008/6/4 Kong Putra <[EMAIL PROTECTED]>:
> Hi budi, dari hasil code yang gw lihat, mungkin ada sedikit yang bisa
> dioptimize.
>
> public class ConversionHelper {
> public static double stringToDouble(String s) {
> char[] cc = s.toCharArray();
> int length = cc.length;
> if (length == 0) {
> return 0;
> }
> int i = 0;
>
> double negation = 1;
> if (cc[0] == '-') {
> negation = -1;
> i++;
> }
>
> int point = -1;
> int value = 0;
> for (; i < length; i++) {
> if (cc[i] == '.') {
> point = i;
> } else {
> value = value * 10 + cc[i] - '0';
> }
> }
>
> int divider = 1;
> if (point > -1) {
> divider = pow10(length - point - 1);
> }
> return negation * value / divider;
> }
>
> public static double stringToDoubleModified(String s) {
> int length = s.length();
> if (length == 0) {
> return 0;
> }
>
> int i = 0;
>
> double negation = 1;
> if (s.charAt(0) == '-'){
> negation = -1;
> i++;
> }
>
> int point = -1;
> int value = 0;
> for (; i < length; i++) {
> char c = s.charAt(i);
> if (c == '.') {
> point = i;
> } else {
> value = value * 10 + c - '0';
> }
> }
>
> int divider = 1;
> if (point > -1) {
> divider = pow10(length - point - 1);
> }
> return negation * value / divider;
> }
>
> private static int pow10(int n) {
>
> int result = 1;
> for (int i = 0; i < n; i++) {
> result *= 10;
> }
>
> return result;
> }
>
> public static void main(String args[]) {
>
> long t1 = System.currentTimeMillis();
> for (int i = 0; i < 1000000; i++) {
> //Double.valueOf("-12.3456");
> //ConversionHelper.stringToDouble("-12.3456");
> ConversionHelper.stringToDoubleModified("-12.3456");
> }
>
> long t2 = System.currentTimeMillis();
> System.out.println("Elapsed time = " + (t2 - t1) + " ms");
>
> }
> }
>
> Memang tidak ada perubahan logic, hanya menghindari penggunaan
> String.toCharArray(), karena method ini cukup boros, didalamnya terdapat
> proses melakukan pembuatan char array baru, dan peng-copy-an char array
> dari String ke char array baru. Hasilnya cukup signifikan, dari test gw
> sktr 30-45 persen lebih cepat dari yang terakhir.
>
> -:regards:-
> Kong Putra
>
> T Budi S wrote:
>>
>> Dear juggers,
>>
>> Mumpung lg hot2nya bahas thread puts vs System.out.println,
>> gw ada 1 challenge utk optimize string to double conversion method
>> dari class java.lang.Double:
>>
>> public static Double valueOf(double d)
>>
>> Kenapa gw butuh utk optimize ini? Krn di project yg sedang gw kerjakan
>> skr, method valueOf memakan 90% ! process time dr keseluruhan process.
>> FYI, data yg dibaca sekitar 10 ribu (nantinya akan jadi ratusan ribu),
>> setiap row terdiri dari 8 column, di mana setiap column-nya berisi
>> data seperti ini:
>>
>>
>> 13.4375:17.1875:22.5:22.8125:23.4375:3:5:4:3:3:3:5:5:3:4:4:5:3:2:6:2:5:3:6:4:2:5:6:3:5:3:2:7:6:5:2:3:6:5:5:2:4:6:4:6:5:3:4:5:3:3:3:5:6:5:2:2:6:7:5:1:3:4:7:6:4:2:1:5:4:3:3:4:5:6:3:1:6:3:5:1:4:2:3:3:3.5:3.75:3.75:4:3.75:3:3.25:5.25:5:5:2.75:2.75:5.25:4.25:5.25:1.5:4:3.75:5:4.75:3:5:3.75:3.5:4.25:2.25:3.5:6.25:4.5:5.25:2.75:2.75:4.75:6.25:4.75:2.75:2.5:3.25:4:4.5:2.75:4.25:5.5:3.75:4.25:2.5:4.25:4.5:4.25:5.25:3.75:2.75:3.5
>>
>> Waktu yg dibutuhkan utk meload semua data ini adalah 4547 ms.
>>
>> Kemudian saya mencoba utk menggantikan Double.valueOf method
>> dgn method bikinan saya sendiri, & mendapatkan hasil 3718 ms.
>>
>> Code-nya adalah sbb:
>>
>> ==============================================
>> public class ConversionHelper
>> {
>>
>> public static double stringToDouble(String s)
>> {
>> char[] cc = s.toCharArray();
>> int length = cc.length;
>> if (length == 0)
>> return 0;
>>
>> int i = 0;
>>
>> double negation = 1;
>> if (cc[0] == '-')
>> {
>> negation = -1;
>> i++;
>> }
>>
>> int point = -1;
>> int value = 0;
>> for (; i<length; i++)
>> {
>> if (cc[i] == '.')
>> point = i;
>> else
>> value = value * 10 + cc[i] - '0';
>> }
>>
>> int divider = 1;
>> if (point > -1)
>> divider = pow10(length - point - 1);
>>
>> return negation * value / divider;
>> }
>>
>> private static int pow10(int n) {
>>
>> int result = 1;
>> for (int i=0; i<n; i++)
>> {
>> result *= 10;
>> }
>>
>> return result;
>> }
>>
>> }
>>
>> ==============================================
>>
>> Ditest dengan looping 1 juta kali:
>> ==============================================
>> @Test
>> public void testPerformance()
>> {
>> long t1 = System.currentTimeMillis();
>> for (int i = 0; i < 1000000; i++)
>> {
>> // Double.valueOf("-12.3456");
>> ConversionHelper.stringToDouble("-12.3456");
>> }
>>
>> long t2 = System.currentTimeMillis();
>> System.out.println("Elapsed time = " + (t2 - t1) + " ms");
>> }
>>
>> ==============================================
>>
>> Hasilnya adalah:
>> - Double.valueof(String): Elapsed time = 344 ms
>> - ConversionHelper.stringToDouble: Elapsed time = 157 ms
>>
>> Sori panjang banget :D Thx kalo udah baca smp di sini.
>> Skr saatnya utk menerima challenge utk mendapatkan hasil yg lebih
>> optimal ;)
>>
>> regards,
>> T Budi S
>>
>>
>
>
