how to combine several matrice into one matrix

[Yujie]

Hi, everyone

Assuming there are A1(M*N) A2(M*N) A3(M*N), I want to get
     A1
A=A2
     A3

My method is

MatGetArray(A1,&a1);
MatSetValues(A,a1);
MatGetArray(A2,&a2);
MatSetValues(A,a2);
MatGetArray(A3,&a3);
MatSetValues(A,a3);

Is there any better methods for it? The above codes are slow. thanks a lot.

Regards,
Yujie
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