Codegen question of qr function

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 ?

Answer 1

[Ryan Livingston]

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.

Answer 2

[alex]

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