Compare classical and modified algorithm of Cholesky












0












$begingroup$


Let $textbf{A}$ be a symmetric matrix with tthe modified Cholesky factorization $textbf{A} = textbf{R}^Ttextbf{D}textbf{R}$ and the classical factorization $textbf{A} = textbf{R}_c^Ttextbf{R}_c$



Given $textbf{R}$ and $textbf{D}$, determine $textbf{R}_c$



$textbf{Proof}$:



Let



$$
textbf{D}^{1/2} = begin{bmatrix}
sqrt{d_1} &&& \
&sqrt{d_2}&&\
&&ddots&\
&&&sqrt{d_n}
end{bmatrix}
$$



Then multiply each row in the modified Cholesky matrix textbf{R} by $sqrt{d_{i,i}}$ to obtain the classical Cholesky matrix



$$
textbf{R}_c = textbf{D}^{1/2}textbf{R}
$$



This is confirmed by



begin{align}
textbf{R}_c^Ttextbf{R}_c &= (textbf{D}^{1/2}textbf{R})^T(textbf{D}^{1/2}textbf{R})tag{1}label{eq1} \
&= textbf{R}^Ttextbf{D}^{1/2}textbf{D}^{1/2}textbf{R}tag{2}label{eq2} \&= textbf{R}^Ttextbf{D}textbf{R}tag{3}label{eq3}
end{align}



What is the name of the property of matrix that allow to go from (1) to (2)










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$endgroup$








  • 1




    $begingroup$
    Distributing a transpose causes order of matrix multiplication to reverse. It's similar to inverse. Also transposing a diagonal matrix does nothing.
    $endgroup$
    – Mark
    Dec 27 '18 at 18:43


















0












$begingroup$


Let $textbf{A}$ be a symmetric matrix with tthe modified Cholesky factorization $textbf{A} = textbf{R}^Ttextbf{D}textbf{R}$ and the classical factorization $textbf{A} = textbf{R}_c^Ttextbf{R}_c$



Given $textbf{R}$ and $textbf{D}$, determine $textbf{R}_c$



$textbf{Proof}$:



Let



$$
textbf{D}^{1/2} = begin{bmatrix}
sqrt{d_1} &&& \
&sqrt{d_2}&&\
&&ddots&\
&&&sqrt{d_n}
end{bmatrix}
$$



Then multiply each row in the modified Cholesky matrix textbf{R} by $sqrt{d_{i,i}}$ to obtain the classical Cholesky matrix



$$
textbf{R}_c = textbf{D}^{1/2}textbf{R}
$$



This is confirmed by



begin{align}
textbf{R}_c^Ttextbf{R}_c &= (textbf{D}^{1/2}textbf{R})^T(textbf{D}^{1/2}textbf{R})tag{1}label{eq1} \
&= textbf{R}^Ttextbf{D}^{1/2}textbf{D}^{1/2}textbf{R}tag{2}label{eq2} \&= textbf{R}^Ttextbf{D}textbf{R}tag{3}label{eq3}
end{align}



What is the name of the property of matrix that allow to go from (1) to (2)










share|cite|improve this question









$endgroup$








  • 1




    $begingroup$
    Distributing a transpose causes order of matrix multiplication to reverse. It's similar to inverse. Also transposing a diagonal matrix does nothing.
    $endgroup$
    – Mark
    Dec 27 '18 at 18:43
















0












0








0





$begingroup$


Let $textbf{A}$ be a symmetric matrix with tthe modified Cholesky factorization $textbf{A} = textbf{R}^Ttextbf{D}textbf{R}$ and the classical factorization $textbf{A} = textbf{R}_c^Ttextbf{R}_c$



Given $textbf{R}$ and $textbf{D}$, determine $textbf{R}_c$



$textbf{Proof}$:



Let



$$
textbf{D}^{1/2} = begin{bmatrix}
sqrt{d_1} &&& \
&sqrt{d_2}&&\
&&ddots&\
&&&sqrt{d_n}
end{bmatrix}
$$



Then multiply each row in the modified Cholesky matrix textbf{R} by $sqrt{d_{i,i}}$ to obtain the classical Cholesky matrix



$$
textbf{R}_c = textbf{D}^{1/2}textbf{R}
$$



This is confirmed by



begin{align}
textbf{R}_c^Ttextbf{R}_c &= (textbf{D}^{1/2}textbf{R})^T(textbf{D}^{1/2}textbf{R})tag{1}label{eq1} \
&= textbf{R}^Ttextbf{D}^{1/2}textbf{D}^{1/2}textbf{R}tag{2}label{eq2} \&= textbf{R}^Ttextbf{D}textbf{R}tag{3}label{eq3}
end{align}



What is the name of the property of matrix that allow to go from (1) to (2)










share|cite|improve this question









$endgroup$




Let $textbf{A}$ be a symmetric matrix with tthe modified Cholesky factorization $textbf{A} = textbf{R}^Ttextbf{D}textbf{R}$ and the classical factorization $textbf{A} = textbf{R}_c^Ttextbf{R}_c$



Given $textbf{R}$ and $textbf{D}$, determine $textbf{R}_c$



$textbf{Proof}$:



Let



$$
textbf{D}^{1/2} = begin{bmatrix}
sqrt{d_1} &&& \
&sqrt{d_2}&&\
&&ddots&\
&&&sqrt{d_n}
end{bmatrix}
$$



Then multiply each row in the modified Cholesky matrix textbf{R} by $sqrt{d_{i,i}}$ to obtain the classical Cholesky matrix



$$
textbf{R}_c = textbf{D}^{1/2}textbf{R}
$$



This is confirmed by



begin{align}
textbf{R}_c^Ttextbf{R}_c &= (textbf{D}^{1/2}textbf{R})^T(textbf{D}^{1/2}textbf{R})tag{1}label{eq1} \
&= textbf{R}^Ttextbf{D}^{1/2}textbf{D}^{1/2}textbf{R}tag{2}label{eq2} \&= textbf{R}^Ttextbf{D}textbf{R}tag{3}label{eq3}
end{align}



What is the name of the property of matrix that allow to go from (1) to (2)







linear-algebra diagonalization symmetry transpose






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asked Dec 27 '18 at 18:41









ecjbecjb

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  • 1




    $begingroup$
    Distributing a transpose causes order of matrix multiplication to reverse. It's similar to inverse. Also transposing a diagonal matrix does nothing.
    $endgroup$
    – Mark
    Dec 27 '18 at 18:43
















  • 1




    $begingroup$
    Distributing a transpose causes order of matrix multiplication to reverse. It's similar to inverse. Also transposing a diagonal matrix does nothing.
    $endgroup$
    – Mark
    Dec 27 '18 at 18:43










1




1




$begingroup$
Distributing a transpose causes order of matrix multiplication to reverse. It's similar to inverse. Also transposing a diagonal matrix does nothing.
$endgroup$
– Mark
Dec 27 '18 at 18:43






$begingroup$
Distributing a transpose causes order of matrix multiplication to reverse. It's similar to inverse. Also transposing a diagonal matrix does nothing.
$endgroup$
– Mark
Dec 27 '18 at 18:43












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