mathjs/test/unit-tests/function/matrix/kron.test.js

// test kronecker product
import assert from 'assert'

import math from '../../../../src/defaultInstance.js'

describe('kron', function () {
  it('should calculate the kronecker product of two arrays', function () {
    assert.deepStrictEqual(math.kron([
      [1, -2, 1],
      [1, 1, 0]
    ], [
      [1, 0],
      [0, 1]
    ]), [
      [1, 0, -2, -0, 1, 0],
      [0, 1, -0, -2, 0, 1],
      [1, 0, 1, 0, 0, 0],
      [0, 1, 0, 1, 0, 0]
    ])
    assert.deepStrictEqual(math.kron([
      [53, 12, -9, 0],
      [2, 2, 5, 2]
    ], [
      [99, 56, 22, 7]
    ]), [
      [5247, 2968, 1166, 371, 1188, 672, 264, 84, -891, -504, -198, -63, 0, 0, 0, 0],
      [198, 112, 44, 14, 198, 112, 44, 14, 495, 280, 110, 35, 198, 112, 44, 14]
    ])
  })

  it('should calculate product for empty 2D Arrays', function () {
    assert.deepStrictEqual(math.kron([[]], [[]]), [[]])
  })

  it('should calculate product for 1D Arrays', function () {
    assert.deepStrictEqual(math.kron([1, 1], [[1, 0], [0, 1]]), [[1, 0, 1, 0], [0, 1, 0, 1]])
    assert.deepStrictEqual(math.kron([[1, 0], [0, 1]], [1, 1]), [[1, 1, 0, 0], [0, 0, 1, 1]])
    assert.deepStrictEqual(math.kron([1, 2, 6, 8], [12, 1, 2, 3]), [[12, 1, 2, 3, 24, 2, 4, 6, 72, 6, 12, 18, 96, 8, 16, 24]])
  })

  it('should support complex numbers', function () {
    assert.deepStrictEqual(math.kron([
      [1, math.complex(0, 1)],
      [math.complex(0, 1), 2]
    ],
    [
      [2, 2],
      [2, 2]
    ]),
    [
      [2, 2, math.complex(0, 2), math.complex(0, 2)],
      [2, 2, math.complex(0, 2), math.complex(0, 2)],
      [math.complex(0, 2), math.complex(0, 2), 4, 4],
      [math.complex(0, 2), math.complex(0, 2), 4, 4]
    ])
  })

  it('should throw an error for greater then 2 dimensions', function () {
    assert.throws(function () {
      math.kron([[[1, 1], [1, 1]], [[1, 1], [1, 1]]], [[[1, 2, 3], [4, 5, 6]], [[6, 7, 8], [9, 10, 11]]])
    })
  })

  it('should throw an error if called with an invalid number of arguments', function () {
    assert.throws(function () { math.kron() }, TypeError)
    assert.throws(function () { math.kron([[1, 2]]) }, TypeError)
  })

  describe('DenseMatrix', function () {
    it('should calculate the kronecker product of a 2d matrix (1)', function () {
      const y = math.matrix([[1, 1], [1, 1]])
      const x = math.matrix([[1, 0], [0, 1]])
      const product = math.kron(x, y)
      assert.deepStrictEqual(product.valueOf(), [[1, 1, 0, 0], [1, 1, 0, 0], [0, 0, 1, 1], [0, 0, 1, 1]])
    })

    it('should calculate the kronecker product of a 2d matrix (2)', function () {
      const y = math.matrix([[1, 2], [55, -1]])
      const x = math.matrix([[13, 0], [0, -1]])
      const product = math.kron(x, y)
      assert.deepStrictEqual(product.toArray(), [[13, 26, 0, 0], [715, -13, 0, -0], [0, 0, -1, -2], [0, -0, -55, 1]])
    })

    it('should throw an error for invalid kronecker product of matrix', function () {
      const y = math.matrix([[[]]])
      const x = math.matrix([[[1, 1], [1, 1]], [[1, 1], [1, 1]]])
      assert.throws(function () { math.kron(y, x) })
    })
  })

  describe('SparseMatrix', function () {
    it('should calculate the kronecker product of a 2d matrix (1)', function () {
      const y = math.sparse([[1, 1], [1, 1]])
      const x = math.sparse([[1, 0], [0, 1]])
      const product = math.kron(x, y)
      assert.deepStrictEqual(product.valueOf(), [[1, 1, 0, 0], [1, 1, 0, 0], [0, 0, 1, 1], [0, 0, 1, 1]])
    })

    it('should calculate the kronecker product of a 2d matrix (2)', function () {
      const y = math.matrix([[1, 2], [55, -1]], 'sparse')
      const x = math.matrix([[13, 0], [0, -1]], 'sparse')
      const product = math.kron(x, y)
      assert.deepStrictEqual(product.toArray(), [[13, 26, 0, 0], [715, -13, 0, -0], [0, 0, -1, -2], [0, -0, -55, 1]])
    })
  })
})