/// <summary>
/// Multiplies the polynomial by another, taking the indices mod N.
/// <para>Does not change this polynomial but returns the result as a new polynomial.
/// Both polynomials must have the same number of coefficients.
/// This method uses the <a href="http://en.wikipedia.org/wiki/Schönhage–Strassen_algorithm"/>
/// Schönhage–Strassen algorithm.</para>
/// </summary>
///
/// <param name="Factor">Multiplication factor</param>
///
/// <returns>Multiplied polynomial</returns>
///
/// <exception cref="CryptoAsymmetricException">Thrown if the two polynomials differ in the number of coefficients</exception>
public BigDecimalPolynomial Multiply(BigIntPolynomial Factor)
{
if (Factor.Coeffs.Length != Coeffs.Length)
{
throw new CryptoAsymmetricException("BigDecimalPolynomial:Multiply", "Number of coefficients must be the same!", new FormatException());
}
BigIntPolynomial poly1 = new BigIntPolynomial(Coeffs.Length);
for (int i = 0; i < Coeffs.Length; i++)
{
poly1.Coeffs[i] = Coeffs[i].UnScaledValue;
}
int scale = Coeffs[0].Scale;
BigIntPolynomial cBigInt = poly1.MultBig(Factor);
BigDecimalPolynomial c = new BigDecimalPolynomial(cBigInt.Coeffs.Length);
for (int i = 0; i < c.Coeffs.Length; i++)
{
c.Coeffs[i] = new BigDecimal(cBigInt.Coeffs[i], scale);
}
return(c);
}
/// <summary>
/// Adds another polynomial which can have a different number of coefficients.
/// </summary>
///
/// <param name="B">The polynomial to add</param>
public void Add(BigDecimalPolynomial B)
{
if (B.Coeffs.Length > Coeffs.Length)
{
int N = Coeffs.Length;
Coeffs = Coeffs.CopyOf(B.Coeffs.Length);
for (int i = N; i < Coeffs.Length; i++)
Coeffs[i] = BigDecimal.Zero;
}
for (int i = 0; i < B.Coeffs.Length; i++)
Coeffs[i] = Coeffs[i].Add(B.Coeffs[i]);
}
/// <summary>
/// Divides each coefficient by a <c>BigDecimal</c> and rounds the result to <c>decimalPlaces</c> places.
/// </summary>
///
/// <param name="Divisor">The divisor</param>
/// <param name="DecimalPlaces">The number of fractional digits to round the result to</param>
///
/// <returns>The polynomial product</returns>
public BigDecimalPolynomial Divide(BigDecimal Divisor, int DecimalPlaces)
{
BigInteger max = MaxCoeffAbs();
int coeffLength = (int)(max.BitLength * LOG_10_2) + 1;
// factor = 1/divisor
BigDecimal factor = BigDecimal.One.Divide(Divisor, coeffLength + DecimalPlaces + 1, RoundingModes.HalfEven);
// multiply each coefficient by factor
BigDecimalPolynomial p = new BigDecimalPolynomial(Coeffs.Length);
for (int i = 0; i < Coeffs.Length; i++)
{
// multiply, then truncate after decimalPlaces so subsequent operations aren't slowed down
p.Coeffs[i] = new BigDecimal(Coeffs[i]).Multiply(factor).SetScale(DecimalPlaces, RoundingModes.HalfEven);
}
return(p);
}
/// <summary>
/// Adds another polynomial which can have a different number of coefficients.
/// </summary>
///
/// <param name="B">The polynomial to add</param>
public void Add(BigDecimalPolynomial B)
{
if (B.Coeffs.Length > Coeffs.Length)
{
int N = Coeffs.Length;
Coeffs = Coeffs.CopyOf(B.Coeffs.Length);
for (int i = N; i < Coeffs.Length; i++)
{
Coeffs[i] = BigDecimal.Zero;
}
}
for (int i = 0; i < B.Coeffs.Length; i++)
{
Coeffs[i] = Coeffs[i].Add(B.Coeffs[i]);
}
}
/// <summary>
/// Multiplies the polynomial by another, taking the indices mod N.
/// <para>Does not change this polynomial but returns the result as a new polynomial.
/// Both polynomials must have the same number of coefficients.
/// This method uses the <a href="http://en.wikipedia.org/wiki/Schönhage–Strassen_algorithm"/>
/// Schönhage–Strassen algorithm.</para>
/// </summary>
///
/// <param name="Factor">Multiplication factor</param>
///
/// <returns>Multiplied polynomial</returns>
///
/// <exception cref="NTRUException">Thrown if the two polynomials differ in the number of coefficients</exception>
public BigDecimalPolynomial Multiply(BigIntPolynomial Factor)
{
if (Factor.Coeffs.Length != Coeffs.Length)
throw new CryptoAsymmetricException("BigDecimalPolynomial:Multiply", "Number of coefficients must be the same!", new FormatException());
BigIntPolynomial poly1 = new BigIntPolynomial(Coeffs.Length);
for (int i = 0; i < Coeffs.Length; i++)
poly1.Coeffs[i] = Coeffs[i].UnScaledValue;
int scale = Coeffs[0].Scale;
BigIntPolynomial cBigInt = poly1.MultBig(Factor);
BigDecimalPolynomial c = new BigDecimalPolynomial(cBigInt.Coeffs.Length);
for (int i = 0; i < c.Coeffs.Length; i++)
c.Coeffs[i] = new BigDecimal(cBigInt.Coeffs[i], scale);
return c;
}
/// <summary>
/// Divides each coefficient by a <c>BigDecimal</c> and rounds the result to <c>decimalPlaces</c> places.
/// </summary>
///
/// <param name="Divisor">The divisor</param>
/// <param name="DecimalPlaces">The number of fractional digits to round the result to</param>
///
/// <returns>The polynomial product</returns>
public BigDecimalPolynomial Divide(BigDecimal Divisor, int DecimalPlaces)
{
BigInteger max = MaxCoeffAbs();
int coeffLength = (int)(max.BitLength * LOG_10_2) + 1;
// factor = 1/divisor
BigDecimal factor = BigDecimal.One.Divide(Divisor, coeffLength + DecimalPlaces + 1, RoundingModes.HalfEven);
// multiply each coefficient by factor
BigDecimalPolynomial p = new BigDecimalPolynomial(Coeffs.Length);
for (int i = 0; i < Coeffs.Length; i++)
{
// multiply, then truncate after decimalPlaces so subsequent operations aren't slowed down
p.Coeffs[i] = new BigDecimal(Coeffs[i]).Multiply(factor).SetScale(DecimalPlaces, RoundingModes.HalfEven);
}
return p;
}
private BigDecimalPolynomial CreateBigDecimalPolynomial(int[] coeffs)
{
int N = coeffs.Length;
BigDecimalPolynomial poly = new BigDecimalPolynomial(N);
for (int i = 0; i < N; i++)
poly.Coeffs[i] = new BigDecimal(coeffs[i]);
return poly;
}