Memory improvements, extra comments.
The result of `multiplier ^ 2` is now written into a single buffer.
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@ -10,18 +10,38 @@ impl<N: ComplexField, D> MatrixN<N, D>
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where
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where
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D: DimMin<D, Output = D>,
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D: DimMin<D, Output = D>,
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DefaultAllocator: Allocator<N, D, D>,
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DefaultAllocator: Allocator<N, D, D>,
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DefaultAllocator: Allocator<N, D>,
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{
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{
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/// Attempts to raise this matrix to an integer power in-place. Returns
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/// Computes the square of this matrix and writes it into a given buffer.
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/// `false` and leaves `self` untouched if the power is negative and the
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fn square_buf(&mut self, buf: &mut Self) {
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/// matrix is non-invertible.
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// We unroll the first iteration to avoid new_uninitialized.
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let mut aux_col = self.column(0).clone_owned();
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aux_col = &*self * aux_col;
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buf.column_mut(0).copy_from(&aux_col);
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// We multiply the matrix by its i-th column,
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for i in 1..self.ncols() {
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aux_col.copy_from(&self.column(i));
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aux_col = &*self * aux_col;
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self.column_mut(i).copy_from(&aux_col);
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}
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}
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/// Attempts to raise this matrix to an integral power `e` in-place. If this
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/// matrix is non-invertible and `e` is negative, it leaves this matrix
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/// untouched and returns `false`. Otherwise, it returns `true` and
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/// overwrites this matrix with the result.
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pub fn pow_mut<T: PrimInt + DivAssign>(&mut self, mut e: T) -> bool {
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pub fn pow_mut<T: PrimInt + DivAssign>(&mut self, mut e: T) -> bool {
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let zero = T::zero();
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let zero = T::zero();
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// A matrix raised to the zeroth power is just the identity.
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if e == zero {
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if e == zero {
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self.fill_with_identity();
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self.fill_with_identity();
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return true;
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return true;
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}
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}
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// If e is negative, we compute the inverse matrix, then raise it to the
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// power of -e.
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if e < zero {
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if e < zero {
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if !self.try_inverse_mut() {
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if !self.try_inverse_mut() {
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return false;
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return false;
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@ -30,22 +50,31 @@ where
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let one = T::one();
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let one = T::one();
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let two = T::from(2u8).unwrap();
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let two = T::from(2u8).unwrap();
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let mut multiplier = self.clone();
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while e != zero {
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// We use the buffer to hold the result of multiplier ^ 2, thus avoiding
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// extra allocations.
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let mut multiplier = self.clone();
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let mut buf = self.clone();
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// Exponentiation by squares.
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loop {
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if e % two == one {
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if e % two == one {
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*self *= &multiplier;
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*self *= &multiplier;
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}
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}
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e /= two;
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e /= two;
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multiplier *= multiplier.clone();
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multiplier.square_buf(&mut buf);
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multiplier.copy_from(&buf);
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if e == zero {
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return true;
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}
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}
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}
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}
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true
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/// Attempts to raise this matrix to an integral power `e`. If this matrix
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}
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/// is non-invertible and `e` is negative, it returns `None`. Otherwise, it
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/// returns the result as a new matrix. Uses exponentiation by squares.
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/// Raise this matrix to an integer power. Returns `None` only if the power
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/// is negative and the matrix is non-invertible.
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pub fn pow<T: PrimInt + DivAssign>(&self, e: T) -> Option<Self> {
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pub fn pow<T: PrimInt + DivAssign>(&self, e: T) -> Option<Self> {
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let mut clone = self.clone();
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let mut clone = self.clone();
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