Matrix Initialization

Here we cover the handful of ways slap provides for initializing matrices.

From an Array

As a lightweight wrapper around a raw double*, Matrix is best initialized from a pointer, along with the size information:

Matrix slap_MatrixFromArray(int rows, int cols, sfloat *data)

Wraps existing data in a Matrix class.

This is the most common way to “create” a matrix. Typical usage will look something like this:

// Stack-allocated memory
sfloat data_stack[24];
Matrix A = slap_MatrixFromArray(6, 4, data_stack);

// Heap-allocated memory
sfloat *data_heap = (sfloat*)malloc(24 * sizeof(sfloat));
Matrix B = slap_MatrixFromArray(6, 4, data_heap);
free(data_heap);
Parameters:

  • rows – Number of rows in the matrix

  • cols – Number of columns in the matrix

  • data – Data for the matrix. Must not be NULL, and should have at least rows * cols elements.

Returns:

A new matrix

Default Initialization

A “default initialized” matrix is considered a “Null” matrix, a internally-defined state (that has a NULL pointer, 0 size, etc.). Use the following methods for creating and checking for Null matrices:

static inline Matrix slap_NullMatrix(void)

Create a “Null” matrix.

Useful for default initialization of the matrix where the data it wraps hasn’t been specified or allocated yet. Can check if a matrix is in this state using slap_IsNull().

Example

Matrix A = slap_NullMatrix();

See also: slap_IsNull(), slap_SetNull()

Returns:

A default “Null” instance of a matrix.

static inline void slap_SetNull(Matrix *mat)

Set a matrix to a “Null” instance.

See also: slap_NullMatrix(), slap_IsNull()

Parameters:

mat – [in] Pointer to the matrix to set to null

static inline bool slap_IsNull(Matrix mat)

Check if matrix is a “Null” instance of a matrix (i.e. uninitialized)

The “Null” state of a matrix is an internally-defined state created by the slap_NullMatrix() method.

See also: slap_NullMatrix(), slap_SetNull()

Parameters:

mat – [in]

Returns:

true if matrix is a “Null” matrix

Allocating Initialization

While all methods in slap assumes the user owns the underlying data, these methods provide some convenient methods for initializing matrices on the heap.

Matrix slap_NewMatrix(int rows, int cols)

Allocate a new matrix on the heap.

Data will not be initialized. Wrapper around a call to malloc. Must be followed by a call to FreeMatrix.

Example

Matrix A = slap_NewMatrix(3,4);
slap_FreeMatrix(A);

Header File: "slap/new_matrix.h"

Parameters:

  • rows – number of rows in the matrix

  • cols – number of columns in the matrix

Returns:

A new matrix

Matrix slap_NewMatrixZeros(int rows, int cols)

Allocate a new matrix on the heap, initialized with zeros.

Data will be initialized to zeros. Wrapper around a call to calloc. Must be followed by a call to FreeMatrix.

Example

Matrix A = slap_NewMatrixZeros(3,4);
slap_FreeMatrix(A);

Header File: "slap/new_matrix.h"

Parameters:

  • rows – number of rows in the matrix

  • cols – number of columns in the matrix

Returns:

A new matrix

enum slap_ErrorCode slap_FreeMatrix(Matrix *mat)

Free the data for a matrix.

Note that this methods takes the pointer to the matrix as a argument, so that it can set the internal data pointer to NULL after the free.

Note this does NOT attempt to free the matrix object itself, only the data it wraps.

Should only be used in conjunction with slap_NewMatrix() or slap_NewMatrixZeros().

Header File: "slap/new_matrix.h"

Note

These functions are NOT included by default when including slap/slap.h, and must be explicitly brought in by including slap/new_matrix.h