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A high-performance general-purpose compute library
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A high-performance general-purpose compute library
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ArrayFire provides several different methods for manipulating arrays and matrices. The functionality includes:
Below we provide several examples of these functions and their use.
The flat() function flattens an array to one dimension:
The flat function can be called from C and C++ as follows:
af_err af_flat(af_array* out, const af_array in) – C interface for flat() function
array af::flat(const array& in) – C++ interface for flat() function
The flip() function flips the contents of an array along a chosen dimension. In the example below, we show the 5x2 array flipped along the zeroth (i.e. within a column) and first (e.g. across rows) axes:
The flip function can be called from C and C++ as follows:
af_err af_flip(af_array *out, const af_array in, const unsigned dim) – C interface for flip()
array af::flip(const array &in, const unsigned dim) – C++ interface for flip()
The join() function joins arrays along a specific dimension. The C++ interface can join up to four arrays whereas the C interface supports up to 10 arrays. Here is an example of how to use join an array to itself:
The join function has several candidate functions in C:
af_err af_join(af_array *out, const int dim, const af_array first, const af_array second) – C interface function to join 2 arrays along a dimension
af_err af_join_many(af_array *out, const int dim, const unsigned n_arrays, const af_array *inputs) – C interface function to join up to 10 arrays along a dimension
and in C++:
array af::join(const int dim, const array &first, const array &second) – Joins 2 arrays along a dimension
array af::join(const int dim, const array &first, const array &second, const array &third) – Joins 3 arrays along a dimension.
array af::join(const int dim, const array &first, const array &second, const array &third, const array &fourth) – Joins 4 arrays along a dimension
The moddims() function changes the dimensions of an array without changing its data or order. Note that this function modifies only the metadata associated with the array. It does not modify the content of the array. Here is an example of moddims() converting an 8x1 array into a 2x4 and then back to a 8x1:
The moddims function has a single form in the C API:
af_err af_moddims(af_array *out, const af_array in, const unsigned ndims, const dim_t *const dims) – C interface to mod dimensions of an array
And several overloaded candidates in the C++ API:
array af::moddims(const array &in, const unsigned ndims, const dim_t *const dims) – mods number of dimensions to match ndims as specidied in the array dims
array af::moddims(const array &in, const dim4 &dims) – mods dimensions as specified by dims
array af::moddims(const array &in, const dim_t d0, const dim_t d1=1, const dim_t d2=1, const dim_t d3=1) – mods dimensions of an array
The reorder() function modifies the order of data within an array by exchanging data according to the change in dimensionality. The linear ordering of data within the array is preserved.
The reorder function has several candidates functions in the C/C++ APIs:
af_err af_reorder(af_array *out, const af_array in, const unsigned x, const unsigned y, const unsigned z, const unsigned w) – C interface for reordering function
array af::reorder(const array &in, const unsigned x, const unsigned y=1, const unsigned z=2, const unsigned w=3) – Reorders dimensions of an array
The shift() function shifts data in a circular buffer fashion along a chosen dimension. Consider the following example:
The shift function can be called from C and C++ as follows:
af_err af_shift(af_array *out, const af_array in, const int x, const int y, const int z, const int w) – C interface for shifting an array
array af::shift(const array &in, const int x, const int y=0, const int z=0, const int w=0) – Shifts array along specified dimensions
The tile() function repeats an array along the specified dimension. For example below we show how to tile an array along the zeroth and first dimensions of an array:
The C interface for tile is as follows:
af_err af_tile(af_array *out, const af_array in, const unsigned x, const unsigned y, const unsigned z, const unsigned w) – C interface for tiling an array
The C++ interface has two overloads
array af::tile(const array &in, const unsigned x, const unsigned y=1, const unsigned z=1, const unsigned w=1) – Tiles array along specified dimensions
array af::tile(const array &in, const dim4 &dims) – Tile an array according to a dim4 object
The transpose() function performs a standard matrix transpose. The input array must have the dimensions of a 2D-matrix.
The C interfaces for transpose are as follows:
af_err af_transpose(af_array *out, af_array in, const bool conjugate) – C interface to transpose a matrix.
af_err af_transpose_inplace(af_array in, const bool conjugate) – C interface to transpose a matrix in-place.
The C++ interface has two primary functions and two shorthand versions:
array af::transpose(const array &in, const bool conjugate=false) – Transposes a matrix.
void af::transposeInPlace(array &in, const bool conjugate=false) – Transposes a matrix in-place.
__array af::T() – Transpose a matrix
__array af::H() – Conjugate Transpose (Hermitian transpose) of a matrix
Here is an example of how the shorthand versions might be used:
array() can be used to create a (shallow) copy of a matrix with different dimensions. The total number of elements must remain the same. This function is a wrapper over the moddims() function discussed earlier.
By using a combination of the array restructuring functions, one can quickly code complex manipulation patterns with a few lines of code. For example, consider generating (x,y) coordinates for a grid where each axis goes from 1 to n. Instead of using several loops to populate our arrays we can just use a small combination of the above functions.
1.9.5