public class SparseObjectMatrix2D extends ObjectMatrix2D
Implementation:
Note that this implementation is not synchronized.
Uses a OpenIntObjectHashMap, which is a compact and performant hashing technique.
Memory requirements:
Cells that
trimToSize().
worst case: memory [bytes] = (1/minLoadFactor) * nonZeros * 13.
best case: memory [bytes] = (1/maxLoadFactor) * nonZeros * 13.
Where nonZeros = cardinality() is the number of non-zero cells.
Thus, a 1000 x 1000 matrix with minLoadFactor=0.25 and maxLoadFactor=0.5 and 1000000 non-zero cells consumes between 25 MB and 50 MB.
The same 1000 x 1000 matrix with 1000 non-zero cells consumes between 25 and 50 KB.
Time complexity:
This class offers expected time complexity O(1) (i.e. constant time) for the basic operations
get, getQuick, set, setQuick and size
assuming the hash function disperses the elements properly among the buckets.
Otherwise, pathological cases, although highly improbable, can occur, degrading performance to O(N) in the worst case.
As such this sparse class is expected to have no worse time complexity than its dense counterpart DenseObjectMatrix2D.
However, constant factors are considerably larger.
Cells are internally addressed in row-major. Performance sensitive applications can exploit this fact. Setting values in a loop row-by-row is quicker than column-by-column, because fewer hash collisions occur. Thus
for (int row=0; row < rows; row++) {
for (int column=0; column < columns; column++) {
matrix.setQuick(row,column,someValue);
}
}
is quicker than
for (int column=0; column < columns; column++) {
for (int row=0; row < rows; row++) {
matrix.setQuick(row,column,someValue);
}
}
cern.colt.map,
OpenIntObjectHashMap,
Serialized FormserialVersionUID| Constructor and Description |
|---|
SparseObjectMatrix2D(int rows,
int columns)
Constructs a matrix with a given number of rows and columns and default memory usage.
|
SparseObjectMatrix2D(int rows,
int columns,
int initialCapacity,
double minLoadFactor,
double maxLoadFactor)
Constructs a matrix with a given number of rows and columns using memory as specified.
|
SparseObjectMatrix2D(Object[][] values)
Constructs a matrix with a copy of the given values.
|
| Modifier and Type | Method and Description |
|---|---|
int |
cardinality()
Returns the number of cells having non-zero values.
|
void |
ensureCapacity(int minCapacity)
Ensures that the receiver can hold at least the specified number of non-zero cells without needing to allocate new internal memory.
|
Object |
getQuick(int row,
int column)
Returns the matrix cell value at coordinate [row,column].
|
ObjectMatrix2D |
like(int rows,
int columns)
Construct and returns a new empty matrix of the same dynamic type as the receiver, having the specified number of rows and columns.
|
ObjectMatrix1D |
like1D(int size)
Construct and returns a new 1-d matrix of the corresponding dynamic type, entirelly independent of the receiver.
|
void |
setQuick(int row,
int column,
Object value)
Sets the matrix cell at coordinate [row,column] to the specified value.
|
void |
trimToSize()
Releases any superfluous memory created by explicitly putting zero values into cells formerly having non-zero values;
An application can use this operation to minimize the
storage of the receiver.
|
aggregate, aggregate, assign, assign, assign, assign, assign, copy, equals, equals, get, getNonZeros, like, set, toArray, toString, viewColumn, viewColumnFlip, viewDice, viewPart, viewRow, viewRowFlip, viewSelection, viewSelection, viewSorted, viewStridescheckShape, checkShape, columns, rows, size, toStringShortclonepublic SparseObjectMatrix2D(Object[][] values)
The values are copied. So subsequent changes in values are not reflected in the matrix, and vice-versa.
values - The values to be filled into the new matrix.IllegalArgumentException - if for any 1 <= row < values.length: values[row].length != values[row-1].length.public SparseObjectMatrix2D(int rows,
int columns)
rows - the number of rows the matrix shall have.columns - the number of columns the matrix shall have.IllegalArgumentException - if rows<0 || columns<0 || (double)columns*rows > Integer.MAX_VALUE.public SparseObjectMatrix2D(int rows,
int columns,
int initialCapacity,
double minLoadFactor,
double maxLoadFactor)
OpenIntObjectHashMap.rows - the number of rows the matrix shall have.columns - the number of columns the matrix shall have.initialCapacity - the initial capacity of the hash map.
If not known, set initialCapacity=0 or small.minLoadFactor - the minimum load factor of the hash map.maxLoadFactor - the maximum load factor of the hash map.IllegalArgumentException - if initialCapacity < 0 || (minLoadFactor < 0.0 || minLoadFactor >= 1.0) || (maxLoadFactor <= 0.0 || maxLoadFactor >= 1.0) || (minLoadFactor >= maxLoadFactor).IllegalArgumentException - if rows<0 || columns<0 || (double)columns*rows > Integer.MAX_VALUE.public int cardinality()
cardinality in class ObjectMatrix2Dpublic void ensureCapacity(int minCapacity)
This method never need be called; it is for performance tuning only. Calling this method before tt>set()ing a large number of non-zero values boosts performance, because the receiver will grow only once instead of potentially many times and hash collisions get less probable.
ensureCapacity in class AbstractMatrixminNonZeros - the desired minimum number of non-zero cells.public Object getQuick(int row, int column)
Provided with invalid parameters this method may return invalid objects without throwing any exception. You should only use this method when you are absolutely sure that the coordinate is within bounds. Precondition (unchecked): 0 <= column < columns() && 0 <= row < rows().
getQuick in class ObjectMatrix2Drow - the index of the row-coordinate.column - the index of the column-coordinate.public ObjectMatrix2D like(int rows, int columns)
like in class ObjectMatrix2Drows - the number of rows the matrix shall have.columns - the number of columns the matrix shall have.public ObjectMatrix1D like1D(int size)
like1D in class ObjectMatrix2Dsize - the number of cells the matrix shall have.public void setQuick(int row,
int column,
Object value)
Provided with invalid parameters this method may access illegal indexes without throwing any exception. You should only use this method when you are absolutely sure that the coordinate is within bounds. Precondition (unchecked): 0 <= column < columns() && 0 <= row < rows().
setQuick in class ObjectMatrix2Drow - the index of the row-coordinate.column - the index of the column-coordinate.value - the value to be filled into the specified cell.public void trimToSize()
Background:
Cells that
trimToSize in class AbstractMatrixJas4pp 1.5 © Java Analysis Studio for Particle Physics