Posts

Showing posts from January, 2016

The WeakReference class, monitoring memory leak and garbage collection in a Java application

-
Image
 Below is a Stack implementation that uses an internal resizeable array structure.  public class MyStack< T > implements Stack< T > { private static final int CAPACITY = 100 ; private Object[] array ; private int pos = 0 ; public MyStack () { this . array = new Object[ CAPACITY ] ; } @Override public void push ( T item) { if ( pos >= array . length / 2 ) { Object[] newArray = new Object[ pos * 2 ] ; System. arraycopy ( array , 0 , newArray , 0 , array . length ) ; array = newArray ; } array [ pos ++] = item ; } @Override public T pop () { if (isEmpty()) { throw new RuntimeException( "empty stack" ) ; } @SuppressWarnings ( "unchecked" ) T item = ( T ) array [ pos - 1 ] ; pos -= 1 ; return item ; } @Override @SuppressWarnings ( "unchecked" ) public T peek...
Post a Comment
Read more

Pulse Motorunun İncelenmesi

-
Pulse sisteminde bir pozisyonun değerlendirilmesi Evaluation sınıfı ile gerçekleşmektedir. class Evaluation { int evaluate(Position position) { int myColor = position. activeColor ; int oppositeColor = opposite(myColor); int value = 0 ; int materialScore = (evaluateMaterial(myColor, position) - evaluateMaterial(oppositeColor, position)) * materialWeight / MAX_WEIGHT; value += materialScore; int mobilityScore = (evaluateMobility(myColor, position) - evaluateMobility(oppositeColor, position)) * mobilityWeight / MAX_WEIGHT; value += mobilityScore; return value; } //... } Burada önce pozisyondaki materyal skoru bulunmaktadır. Örneğin bir piyon fazlası var ise materyal skoru 1 olarak bulunur. Ardından mobilite skoru bulunmaktadır. Örneğin bir fil, çapraz karelerde serbest olarak dolaşabiliyorsa mobilite skoru yüksek olur. Satranç motorları güçlendikçe değerlendirme kriterleri de artmakta ve kod d...
Post a Comment
Read more

FEN Notasyonu ve UCI Protokolü

-
FEN NOTASYONU Forsyth-Edwards Notasyonu, satranç pozisyonlarını ASCII karakter seti kullanarak ifade etmeye yarayan bir standarttır. Satranç programcıları için standart bir pozisyon notasyonu çok önemlidir çünkü böylece pozisyon veritabanlarını birbirleri ile paylaşabilirler. Satranç motorlarının test edilmesinde bu veritabanları önemli yer tutar ve yorucu veri girişi işlemlerinden kurtulmayı sağlar. [1] FEN tanımlaması tek satırdan oluşur ve 6 alandan ibarettir: İlk alan, taşların yerleşimini ifade eder. Taşların dizilimi 8. satırdan başlanarak gösterilir. Beyaz taşlar için "PNBRQK" şeklinde büyük harfler kullanılırken, siyah taşlar için küçük harfler kullanılır. İkinci alan aktif rengi ifade etmektedir. Eğer sıra beyazda ise "w" değerini alır. Üçüncü alan rok yapma iznini ifade eder. Eğer her iki taraf da rok yapamıyorsa "-" değerini alır. Eğer beyaz, şah tarafına rok yapabiliyorsa "K", vezir tarafına rok yapabiliyo...
Post a Comment
Read more

Notes on Parallel Programming

-
In the past, the performance of microprocessors increased on average, 50% per year. In this period, you could simply wait to buy the next generation of microprocessors that will speed up your applications. But since 2002, single processor performance has slowed down. By 2005, most manufacturers decided to go on in the direction of paralellism. They started to put multiple processors on a single circuit. But this does not magically improve the performance of serial applications. It may be a silly question to ask: why do we need ever increasing performance? But why do they manufacture multi-core hardware? Because as the speed of transistor increase, so does the power consumption. The circuit becomes too hot and is not reliable anymore. And if the integrated circuit industry stop producing new and better products, those companies dissapear. So today, CPU clock speed is not increasing, and manufacturers does not design complex processors. Most of the time, it is not possible to automat...
Post a Comment
Read more

Popular posts from this blog

Trie Data Structure and Finding Patterns in a Collection of Words

-
Image
 I faced a very hard problem recently about finding substrings based on a collection of patterns.  Example For  words = ["Apple", "Melon", "Orange", "Watermelon"]  and  parts = ["a", "mel", "lon", "el", "An"] , the output should be  findSubstrings(words, parts) = ["Apple", "Me[lon]", "Or[a]nge", "Water[mel]on"] . While  "Watermelon"  contains three substrings from the  parts  array,  "a" ,  "mel" , and  "lon" ,  "mel"  is the longest substring that appears first in the string. Note: Number of words and number of parts can be huge! A brute force method or careless usage of Java String methods would make it impossible to handle a large number of words and parts (patterns). Solution Approach Whenever we want to search patterns inside a string, we should think about the Trie data structure:  https://en.wikipedia....
Read more

My Crappy Looking Solution to "Binary Tree Common Ancestor" Problem

-
I was able to solve this problem and make all the tests pass: https://www.hackerrank.com/challenges/binary-search-tree-lowest-common-ancestor/problem But I'm not happy with the code, so later I need to refactor the code. Here it is: static Node lca(Node root, int v1, int v2) { ArrayList result = new ArrayList<>(); Node result2 = traverse (root, v1, v2, result); if (result.isEmpty()) return result2; return result.get( 0 ); } private static Node traverse(Node root, int v1, int v2, ArrayList result) { if (!result.isEmpty()) { return result.get( 0 ); } if (root. left == null && root. right == null ) { return root; } if (root. data == v1 || root. data == v2) { return root; } Node node1 = null , node2 = null ; if (root. left != null ) node1 = traverse (root. left , v1, v2, result); if (root. right != null ) node2 = traverse (root. right , v1, v...
Read more

A Graph Application in Java: Using WordNet to Find Outcast Words

-
Image
I'll explain our intent with an example: Let's say we have the following words: horse, zebra, cat, bear, table Which one is the outcast? The table.. But how can a computer system find this? We are talking about the whole English language and any word can be in this list. The number of words in the list can be huge, so the solution should use appropriate data structures and algorithms.  We'll use WordNet which is a graph of English words. It contains the semantic relationships between words and our concern is the "is a" relationship. For our example, we know that horse and cat are both animals. "Table" is not an animal and it is the outcast in this situation. But we even have the ability to tell that horse and zebra is very close. Below is a unit test that shows a high level view of our application in Java: public class OutcastTest {     private WordNet wordNet;     private Outcast outcast;     @Before ...
Read more