Components
Core Components
NDArray

Multi-dimensional arrays

C++17 Header-only library for basic operations with multidimensional arrays.

Basic usage

green-ndarray is a C++ header-only library that provides basic routines to operate with multi-dimensional data. It allows to create a multidimensional array that owns memory, as well as an array for an allocated memory.

To add this library into your project, first.

Include(FetchContent)

FetchContent_Declare(
        green-ndarray
        GIT_REPOSITORY https://github.com/Green-Phys/green-ndarray.git
        GIT_TAG origin/main # or a later release
)
FetchContent_MakeAvailable(green-ndarray)

Add predefined alias GREEN::NDARRAY it to your target:

target_link_libraries(<target> PUBLIC GREEN::NDARRAY)

And then simply include the following header:

#include <green/ndarray/ndarray.h>

Here is a small example of some possible operations:

using namespace green::ndarray;

// Create empty 5d array of doubles
ndarray<double, 5> array1;

// Resize array to a new shape
array1.resize(3,4,5,6,7);

// Set all elements of array to be 3

array1 = 3.0;

// Create 5d array of doubles of shape (3,4,5,6,7) and set all elements to 1
ndarray<double, 5> array2(3,4,5,6,7);
array2 = 1.0;

// Take a 2-dimesional slice of array1 at (1,2,3) leading index
// Both array1 and array3 point at the same memory region.
// array3 has a non-zero offset from the beginning of a memory region
ndarray<double, 2> array3 = array1(1,2,3);

// Get an element of array2 at (1,2,3,4,5) coordinate

double value = array2(1,2,3,4,5);

Assignment operation does not do deep copy of the data. Example below shows possible scenarios for assignment and deep-copy of the data.

// Create empty 5-dimensional array
ndarray<double, 5> array4;

// array4 shares memory with array1, any changes in array4 will be changes in array1
array4 = array1;

// Create empty 5-dimensional array
ndarray<double, 5> array5;

// Make a deep copy of array1 and assign it to array5

array5 = array1.copy();

// Create an array of the same shape as array1
ndarray<double, 5> array6(3,4,5,6,7);

// Assign all elements of array1 to array6
array6 << array1;

Keep in mind that operator<< requires both arrays to have the same shape. This check is enfourced in Debug mode and. omitted in Release mode for performance reasons.

To perform basic mathematic operations you need to include <green/ndarray/ndarray_math.h> header.

The following operations are implemented

  • Addition and Subtraction
  • Inplace Addition and Subtraction
  • Addition and Subtraction of a scalar
  • Multiplication and Division by a scalar
  • Inplace operations with scalar
  • Negation of an array

Datatypes of two operands do not need to be the same. For inplace operations value type of a RHS should be. convertible to a value type of a RHS array. For non-inplace operation an array of common value type for both operands.

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