Codegen question of qr function

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alex
alex 2013-1-28
Hi
I am trying to convert QR decomposition (qr) function to convert in c using codegen but it producing the wrong code .
I am using this command line
codegen -args {coder.typeof(double(0), [1 Inf])} -report -config:lib qr -O disable:inline
% code
static void eml_qr(const emxArray_real_T *A, real_T Q_data[1], int32_T Q_size[2],emxArray_real_T *R, emxArray_real_T *E)
that produce the qr function with all arguments are dynamic array but second parameter Q_data is static array ?

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回答（2 个）

Ryan Livingston
Ryan Livingston 2013-1-28
Given an m-by-n array A, QR produces a Q which is m-by-m. In this case the declaration:
coder.typeof(double(0), [1 Inf])
says that A is 1-by-? (i.e. a row vector with an unknown number of elements). Therefore, it can be determined that Q is a scalar without need for dynamic sizing.
I would also point out that the generated function "eml_qr" is created from an internal function called by the implementation of QR. In my opinion, it would be advisable to interface with the function:
qr(const emxArray_real_T *A, double Q_data[1], int Q_size[2], emxArray_real_T *R, emxArray_real_T *E);
in case the internal implementation of QR changes.
alex
alex 2013-1-29
Thank you Ryan for the hint.
Finally i managed to get c code working using this command-line
codegen -args {coder.typeof(double(0), [Inf Inf])} -report -config:lib qr -O disable:inline

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