大型矩阵的java.lang.OutOfMemoryError

Question

I have int K as an input (K will be between 0 and 1000000 (one million), inclusive) and I would like then to create a matrix of integers with height and width 2 times longer than K number, plus 1 element more.

Example if K=3, my matrix would be matrix[3*2+1][3*2+1]=matrix[7][7] if K=178754, my matrix would be matrix[357503][357503]

I got an java.lang.OutOfMemoryError: Java heap space exception in thread "main"

int height;
int width;
int [][] matrix;

    public int getKthNumber(int N, int K, String direction) {

    this.height = (K * 2) + 1;
    this.width = (K * 2) + 1;

    ****matrix = new int[this.width][this.height];****   // error here

Does anyone knows how to solve this little problem since I believe that the whole other code is OK ??

Answer 1

my matrix would be matrix[357503][357503]

Yes .That's all enough to get out of memory. JVM tries to allocate memory for 357503X357503 of integers, where as each integer carries 32 bits which resulting ~476GB almost.

What actually you are trying to do ?

Answer 2

In a 32 bit system you can have up to 2GB . On a 64 bit system you can get more.

Command line flags are:

java -Xmx2g myprogram

But in your case it seems that this will not be enough, since 357503*357503*4/1024/1024/1024 (4 for bytes for integer) which is about 476G, so I think that you should rethink your solution.