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https://github.com/uestla/sparse-matrix
C++ implementation of sparse matrix using CRS (Compressed Row Storage) format
https://github.com/uestla/sparse-matrix
cpp crs matrix sparse
Last synced: about 2 months ago
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C++ implementation of sparse matrix using CRS (Compressed Row Storage) format
- Host: GitHub
- URL: https://github.com/uestla/sparse-matrix
- Owner: uestla
- Created: 2014-03-23T23:51:49.000Z (almost 11 years ago)
- Default Branch: master
- Last Pushed: 2020-08-08T18:21:32.000Z (over 4 years ago)
- Last Synced: 2023-03-12T17:15:39.065Z (almost 2 years ago)
- Topics: cpp, crs, matrix, sparse
- Language: C++
- Homepage:
- Size: 95.7 KB
- Stars: 92
- Watchers: 7
- Forks: 47
- Open Issues: 8
-
Metadata Files:
- Readme: README.md
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README
# Sparse Matrix
C++ implementation of sparse matrix using [CRS format](http://netlib.org/linalg/html_templates/node91.html#SECTION00931100000000000000).
[](https://www.paypal.com/cgi-bin/webscr?cmd=_s-xclick&hosted_button_id=KWQJ7VTXZMZLS)
## Usage
### Creation
SparseMatrix comes as a template class, so we have to specify the element type.
```cpp
SparseMatrix::SparseMatrix matrix(3); // 3×3 matrix of integers
SparseMatrix::SparseMatrix matrix2(4, 5); // 4×5 matrix - 4 rows, 5 columns
SparseMatrix::SparseMatrix matrix3(matrix); // copy constructor
SparseMatrix::SparseMatrix matrix4 = matrix2; // deep copy assignment
```
All values are now equal to `()`, which for type `int` is `0`.
### Values
To set or get value, use methods `set()` and `get()`:
```cpp
int val;
matrix.set(-5, 2, 3); // sets -5 on 2nd row and 3rd column
val = matrix.get(2, 3); // val = -5
val = matrix.get(1, 1); // val = 0
```
When accessing invalid coordinates, `InvalidCoordinatesException` is thrown. Please note that **rows and columns are indexed from 1**.
### Operations
SparseMatrix is implemented as an immutable object - all operations create new matrix instead of changing the matrix the operation is called on.
#### Matrix-Vector multiplication
Number of columns in the matrix has to be the same as the size of the vector, otherwise `InvalidDimensionsException` is thrown.
```cpp
SparseMatrix::SparseMatrix mat(4, 5);
std::vector vec(5, 2);
std::vector result;
result = mat.multiply(vec); // method
result = mat * vec; // operator
```
#### Matrix-Matrix multiplication
Number of columns in the left matrix must be same as number of rows in the right matrix, otherwise `InvalidDimensionsException` is thrown.
```cpp
SparseMatrix::SparseMatrix matrixA(2, 3);
SparseMatrix::SparseMatrix matrixB(3, 4);
SparseMatrix::SparseMatrix product; // will be of size 2×4
product = matrixA.multiply(matrixB); // method
product = matrixA * matrixB; // operator
```
#### Matrix-Matrix addition / subtraction
You can also add and subtract matrices together. Both matrices has to have same dimentions, otherwise `InvalidDimensionsException` is thrown.
```cpp
SparseMatrix::SparseMatrix matrixA(4, 7);
SparseMatrix::SparseMatrix matrixB(4, 7);
SparseMatrix::SparseMatrix sum;
sum = matrixA.add(matrixB); // method
sum = matrixA + matrixB; // operator
SparseMatrix::SparseMatrix diff;
diff = matrixA.subtract(matrixB); // method
diff = matrixA - matrixB; // operator
```
#### Matrix-Matrix comparison
```cpp
SparseMatrix::SparseMatrix matrixA(3);
SparseMatrix::SparseMatrix matrixB(3);
bool areSame = matrixA == matrixB; // true
```
#### Dimensions
To access matrix dimensions use simple getters:
```cpp
int rows = matrix.getRowCount();
int cols = matrix.getColumnCount();
```
#### Printing matrix
Basic output streaming is implemented. Note that output operator must be implemented for the element type as well.
```cpp
SparseMatrix::SparseMatrix matrix(3, 4);
matrix.set(2, 1, 1);
matrix.set(7, 1, 3);
matrix.set(4, 2, 2);
matrix.set(1, 3, 4);
std::cout << matrix << std::endl;
/*
2 0 7 0
0 4 0 0
0 0 0 1
*/
```
### Custom element type
If integers/floats are not enough, you can always use your own element type.
Make sure your type implements:
* empty constructor (which represents the zero value)
* copying constructor
* comparison `operator ==` so that it is possible to tell whether a value is zero-ish
* adding `operator +`
* subtracting `operator -`
* product `operator *`
* output `operator <<` to be able to nicely output the matrix
You can see a simple custom element example in [the tests](tests/cases/custom-type.cpp).
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Any questions / issues / pull requests / [donations](https://www.paypal.com/cgi-bin/webscr?cmd=_s-xclick&hosted_button_id=KWQJ7VTXZMZLS) are very welcome! :-)