View Compilation Error

0_0_3281605_24147.cpp: In function `Mat operator+(Mat, Mat)':
0_0_3281605_24147.cpp:44: error: `sz' undeclared (first use this function)
0_0_3281605_24147.cpp:44: error: (Each undeclared identifier is reported only once for each function it appears in.)
0_0_3281605_24147.cpp: In function `Mat operator*(Mat, Mat)':
0_0_3281605_24147.cpp:53: error: `zero' undeclared (first use this function)
0_0_3281605_24147.cpp:54: error: `sz' undeclared (first use this function)
0_0_3281605_24147.cpp: In function `int main()':
0_0_3281605_24147.cpp:113: error: `solve' undeclared (first use this function)