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Factor square Hermitian positive definite matrix into triangular components
The Cholesky Factorization block uniquely factors the square Hermitian positive definite input matrix S as
$$S=L{L}^{*}$$
where L is a lower triangular square matrix with positive diagonal elements and L^{*} is the Hermitian (complex conjugate) transpose of L. The block outputs a matrix with lower triangle elements from L and upper triangle elements from L^{*}. The output is not in the same form as the output of the MATLAB^{®} chol function. In order to convert the output of the Cholesky Factorization block to the MATLAB form, use the following equation:
R = triu(LL');
Here, LL' is the output of the Cholesky Factorization block. Due to roundoff error, these equations do not produce a result that is exactly the same as the MATLAB result.
Block Output Composed of L and L^{*}
The block output is valid only when its input has the following characteristics:
Hermitian — The block does not check whether the input is Hermitian; it uses only the diagonal and upper triangle of the input to compute the output.
Realvalued diagonal entries — The block disregards any imaginary component of the input's diagonal entries.
Positive definite — Set the block to notify you when the input is not positive definite as described in Response to Nonpositive Definite Input.
To generate a valid output, the block algorithm requires a positive definite input (see Input Requirements for Valid Output). Set the Nonpositive definite input parameter to determine how the block responds to a nonpositive definite input:
Ignore — Proceed with the computation and do not issue an alert. The output is not a valid factorization. A partial factorization will be present in the upper left corner of the output.
Warning — Display a warning message in the MATLAB Command Window, and continue the simulation. The output is not a valid factorization. A partial factorization will be present in the upper left corner of the output.
Error — Display an error dialog and terminate the simulation.
Note The Nonpositive definite input parameter is a diagnostic parameter. Like all diagnostic parameters on the Configuration Parameters dialog box, it is set to Ignore in the code generated for this block by Simulink^{®} Coder™ code generation software. 
Note that L and L^{*} share the same diagonal in the output matrix. Cholesky factorization requires half the computation of Gaussian elimination (LU decomposition), and is always stable.
Response to nonpositive definite matrix inputs: Ignore, Warning, or Error. See Response to Nonpositive Definite Input.
Golub, G. H., and C. F. Van Loan. Matrix Computations. 3rd ed. Baltimore, MD: Johns Hopkins University Press, 1996.
Port  Supported Data Types 

S 

LL' 

DSP System Toolbox  
DSP System Toolbox  
DSP System Toolbox  
DSP System Toolbox  
DSP System Toolbox  
DSP System Toolbox  
MATLAB 
See Matrix Factorizations for related information.