Hello, I used Matlab coder to translate some Matlab code into C++. The C++ generated code produces different result from the original Matlab code. I traced the C++ code and found out the problem is with matrix multiplication. I tried a simple code to make sure the bug is not related to my Matlab code and still getting wrong result from generated code. Here is the Matlab code:
function [Final Delta] = Test_Coder(x,y,w)
Delta = x*y;
Final= Delta * w;
end
and this is the script that calls the function:
clear all
clc
x = [2,4;5,6];
y = [7,3;5,1];
w = [3;5];
[Final Delta] = Test_Coder(x,y,w)
Here is the generated C++ code ("printf" instructions are added later for debugging purpose):
// 'Test_Coder:3' Delta = x*y;
for (i0 = 0; i0 < 2; i0++) {
for (i1 = 0; i1 < 2; i1++) {
Delta[i0 + (i1 << 1)] = 0.0;
for (i2 = 0; i2 < 2; i2++) {
Delta[i0 + (i1 << 1)] += x[i0 + (i2 << 1)] * y[i2 + (i1 << 1)];
printf("\n Delta[%d] += x[%d] * y[%d] = %lf * %lf >> %lf ",i0 + (i1 << 1),i0 + (i2 << 1) ,i2 + (i1 << 1), x[i0 + (i2 << 1)],y[i2 + (i1 << 1)] ,Delta[i0 + (i1 << 1)]);
}
}
// 'Test_Coder:5' Final= Delta * w;
Final[i0] = 0.0;
for (i1 = 0; i1 < 2; i1++) {
Final[i0] += Delta[i0 + (i1 << 1)] * w[i1];
printf("\n Final[%d] += Delta[%d] * w[%d] = %lf * %lf >> %lf ",i0, i0 + (i1 << 1), i1, Delta[i0 + (i1 << 1)], w[i1], Final[i0]);
}
}
}
This is Matlab generated results:
Final =
152
300
Delta =
34 10
65 21
and here is C++ results:
Delta[0] += x[0] * y[0] = 2.000000 * 7.000000 >> 14.000000
Delta[0] += x[2] * y[1] = 5.000000 * 3.000000 >> 29.000000
Delta[2] += x[0] * y[2] = 2.000000 * 5.000000 >> 10.000000
Delta[2] += x[2] * y[3] = 5.000000 * 1.000000 >> 15.000000
Final[0] += Delta[0] * w[0] = 29.000000 * 15.000000 >> 435.000000
Final[0] += Delta[2] * w[1] = 15.000000 * 5.000000 >> 510.000000
Delta[1] += x[1] * y[0] = 4.000000 * 7.000000 >> 28.000000
Delta[1] += x[3] * y[1] = 6.000000 * 3.000000 >> 46.000000
Delta[3] += x[1] * y[2] = 4.000000 * 5.000000 >> 20.000000
Delta[3] += x[3] * y[3] = 6.000000 * 1.000000 >> 26.000000
Final[1] += Delta[1] * w[0] = 46.000000 * 15.000000 >> 690.000000
Final[1] += Delta[3] * w[1] = 26.000000 * 26.000000 >> 1366.000000
Any idea what is wrong and how to fix it? I am using Matlab R2015a.
Thanks, Ali
