public void ShouldCreatePolynomialFromPolyhaseComponents(int[] evenComponentCoefficients, int[] oddComponenetCoefficients,
int[] expectedPolynomialCoefficients)
{
// Given
var evenComponent = new Polynomial(_field, evenComponentCoefficients);
var oddComponent = new Polynomial(_field, oddComponenetCoefficients);
var expectedPolynomial = new Polynomial(_field, expectedPolynomialCoefficients);
// When
var actualPolynomial = PolynomialsAlgorithmsExtensions.CreateFormPolyphaseComponents(evenComponent, oddComponent);
// Then
Assert.Equal(expectedPolynomial, actualPolynomial);
}
/// <summary>
/// Method for building complementary polynomial for polynomial <paramref name="sourceFilter"/> with coefficients count <paramref name="maxFilterLength"/>
/// </summary>
/// <param name="sourceFilter">Polynomial for which complementary polynomial should be built</param>
/// <param name="maxFilterLength">Coefficients count in complementary polynomial</param>
/// <returns>Built complementary polynomial</returns>
public Polynomial Build(Polynomial sourceFilter, int maxFilterLength)
{
if (sourceFilter == null)
{
throw new ArgumentNullException(NameOfExtension.nameof(() => sourceFilter));
}
var polythaseComponents = sourceFilter.GetPolyphaseComponents();
var gcdWithQuotients = _gcdFinder.GcdWithQuotients(polythaseComponents.Item1, polythaseComponents.Item2);
if (gcdWithQuotients.Gcd.IsMonomial() == false)
{
throw new InvalidOperationException(sourceFilter + " polyphase components is not relatively prime");
}
var field = sourceFilter.Field;
var complementaryFilterEvenComponent = new Polynomial(field);
var complementaryFilterOddComponent = field.Pow(field.InverseForAddition(1), gcdWithQuotients.Quotients.Length)
* InvertGcdInPolynomialsRing(gcdWithQuotients.Gcd, (maxFilterLength + 1) / 2);
for (var i = gcdWithQuotients.Quotients.Length - 1; i > -1; i--)
{
var complementaryFilterEvenComponentOld = complementaryFilterEvenComponent;
complementaryFilterEvenComponent = gcdWithQuotients.Quotients[i] * complementaryFilterEvenComponentOld
+ complementaryFilterOddComponent;
complementaryFilterOddComponent = complementaryFilterEvenComponentOld;
}
var m = new Polynomial(field, 1).RightShift(maxFilterLength);
m[0] = field.InverseForAddition(1);
return(PolynomialsAlgorithmsExtensions.CreateFormPolyphaseComponents(
complementaryFilterEvenComponent,
complementaryFilterOddComponent
) % m);
}
