Class IntArray2D

java.lang.Object

smile.util.IntArray2D

public class IntArray2D
extends Object

2-dimensional array of integers. Java doesn't have real multidimensional arrays. They are just array of arrays, which are not friendly to modern CPU due to frequent cache miss. The extra (multiple times) array index checking also significantly reduces the performance. This class solves these pain points by storing data in a single 1D array of int in row major order. Note that this class is simple by design, as a replacement of int[][] in case of row by row access. For advanced matrix computation, please use Matrix.

See Also:

• Matrix

Constructor Summary

Constructors

Constructor	Description
IntArray2D(int[][] A)	Constructor.
IntArray2D(int nrow, int ncol)	Constructor of all-zero matrix.
IntArray2D(int nrow, int ncol, int value)	Constructor.
IntArray2D(int nrow, int ncol, int[] value)	Constructor.

Method Summary

Modifier and Type	Method	Description
IntArray2D	add(int x)	A += x.
int	add(int i, int j, int x)	A[i, j] += x.
IntArray2D	add(IntArray2D B)	A += B.
int	apply(int i, int j)	Returns A[i, j].
IntArray2D	div(int x)	A /= x.
int	div(int i, int j, int x)	A[i, j] /= x.
IntArray2D	div(IntArray2D B)	A /= B.
int	get(int i, int j)	Returns A[i, j].
IntArray2D	mul(int x)	A *= x.
int	mul(int i, int j, int x)	A[i, j] *= x.
IntArray2D	mul(IntArray2D B)	A *= B.
int	ncol()	Returns the number of columns.
int	nrow()	Returns the number of rows.
void	set(int i, int j, int x)	Sets A[i, j].
IntArray2D	sub(int x)	A -= x.
int	sub(int i, int j, int x)	A[i, j] -= x.
IntArray2D	sub(IntArray2D B)	A -= B.
long	sum()	Returns the sum of all elements.
String	toString()
String	toString(boolean full)	Returns the string representation of matrix.
String	toString(int m, int n)	Returns the string representation of matrix.

Methods inherited from class Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Constructor Details

IntArray2D

public IntArray2D(int[][] A)

Constructor.

Parameters:

A - the array of matrix.

IntArray2D

public IntArray2D(int nrow,
 int ncol)

Constructor of all-zero matrix.

Parameters:

nrow - the number of rows.

ncol - the number of columns.

IntArray2D

public IntArray2D(int nrow,
 int ncol,
 int value)

Constructor. Fill the matrix with given value.

Parameters:

nrow - the number of rows.

ncol - the number of columns.

value - the initial value.

IntArray2D

public IntArray2D(int nrow,
 int ncol,
 int[] value)

Constructor.

Parameters:

nrow - the number of rows.

ncol - the number of columns.

value - the array of matrix values arranged in row major format.

Method Details

nrow

public int nrow()

Returns the number of rows.

Returns:

the number of rows.

ncol

public int ncol()

Returns the number of columns.

Returns:

the number of columns.

apply

public int apply(int i,
 int j)

Returns A[i, j]. Useful in Scala.

Parameters:

i - the row index.

j - the column index.

Returns:

A[i, j].

get

public int get(int i,
 int j)

Returns A[i, j].

Parameters:

i - the row index.

j - the column index.

Returns:

A[i, j].

set

public void set(int i,
 int j,
 int x)

Sets A[i, j].

Parameters:

i - the row index.

j - the column index.

x - the value.

add

public int add(int i,
 int j,
 int x)

A[i, j] += x.

Parameters:

i - the row index.

j - the column index.

x - the operand.

Returns:

the updated cell value.

sub

public int sub(int i,
 int j,
 int x)

A[i, j] -= x.

Parameters:

i - the row index.

j - the column index.

x - the operand.

Returns:

the updated cell value.

mul

public int mul(int i,
 int j,
 int x)

A[i, j] *= x.

Parameters:

i - the row index.

j - the column index.

x - the operand.

Returns:

the updated cell value.

div

public int div(int i,
 int j,
 int x)

A[i, j] /= x.

Parameters:

i - the row index.

j - the column index.

x - the operand.

Returns:

the updated cell value.

add

public IntArray2D add(IntArray2D B)

A += B.

Parameters:

B - the operand.

Returns:

this object.

sub

public IntArray2D sub(IntArray2D B)

A -= B.

Parameters:

B - the operand.

Returns:

this object.

mul

public IntArray2D mul(IntArray2D B)

A *= B.

Parameters:

B - the operand.

Returns:

this object.

div

public IntArray2D div(IntArray2D B)

A /= B.

Parameters:

B - the operand.

Returns:

this object.

add

public IntArray2D add(int x)

A += x.

Parameters:

x - the operand.

Returns:

this object.

sub

public IntArray2D sub(int x)

A -= x.

Parameters:

x - the operand.

Returns:

this object.

mul

public IntArray2D mul(int x)

A *= x.

Parameters:

x - the operand.

Returns:

this object.

div

public IntArray2D div(int x)

A /= x.

Parameters:

x - the operand.

Returns:

this object.

sum

public long sum()

Returns the sum of all elements.

Returns:

the sum of all elements.

toString

public String toString()

Overrides:

toString in class Object

toString

public String toString(boolean full)

Returns the string representation of matrix.

Parameters:

full - Print the full matrix if true. Otherwise, print only top left 7 x 7 submatrix.

Returns:

the string representation of matrix.

toString

public String toString(int m,
 int n)

Returns the string representation of matrix.

Parameters:

m - the number of rows to print.

n - the number of columns to print.

Returns:

the string representation of matrix.