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PODifferent results calculating the average of double variables contained in a vector of structs by altering code formatting?
 

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  1. PODifferent results calculating the average of double variables contained in a vector of structs by altering code formatting?
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    <p>I am currently fighting with a very odd behavior of OpenCV/C++. This is what i am doing:</p> <p>Updated 1: Here more informations:</p> <p>I calculate the gradient orientation for a set of pixels and store them in a <code>double</code> field of a self declared <code>struct</code>. The struct elements get stored in a vector.</p> <pre><code>myfunct1() { (...) c.grad_orientation = (sum_ori / highgrads.size()) + M_PI; // +M_PI because i just want to rotate the angle around 180°. (...) my_struct_vector.push_back(c); } </code></pre> <p>I later got several <code>c</code> stored in a vector and want to estimate the average of every single <code>grad_orientation</code>, stored in every struct-element of my vector looking like this:</p> <pre><code>myfunct0() { myfunct1(); //adds element to the my_struct_vector (...) int n = 0; double total_ori = 0.0; for (uint i = 0; i &lt; my_struct_vector.size(); ++i) { total_ori += my_struct_vector[i].grad_orientation; n++; } azimuth = (total_ori / n); cout &lt;&lt; "Average: " &lt;&lt; azimuth * 180/M_PI &lt;&lt; endl; // print out in degrees } </code></pre> <p>Now for the funny part: If i do this under certain circumstances, the <code>cout</code> prints <code>215.963</code>. This is the result i got most often (EXACTLY this result). In some cases, if i add these matrices named above or (yes, really) if i move the double field holding the <code>grad_orientation</code> in the struct one column higher in terms of code i get <code>223.442</code>. So the difference between the two results in the code is <em>only</em> the following:</p> <pre><code>struct my_struct { std::vector&lt;cv::Point&gt; contour_shadow; std::vector&lt;cv::Point&gt; contour_light; cv::RotatedRect rect; cv::Point pf; cv::Point pc; double grad_orientation; // this line moved one column down, beneath "grad_flag" results in a differing result. bool grad_flag; double grad_magnitude; </code></pre> <p>};</p> <p>The printed results do not only depend on the position of the column in the struct declaration but also when i alter different parts of my code.</p> <p>This may has something to do with double precision, but why does it alter if i move columns of code?</p>
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    1. USmoatilliatta
    1. USmoatilliatta
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      1. PODifferent results calculating the average of double variables contained in a vector of structs by altering code formatting?
      1. USmoatilliatta
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      1. VTUpMod
    1. COSounds like some buffer overrunning. Hard to tell without seeing the code that declares your image variables, and the operations performed on them between their instantiation and the function calls above.
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      1. PODifferent results calculating the average of double variables contained in a vector of structs by altering code formatting?
      1. USRook
    2. COexamine how you do the loop. the finishing criteria is craters.size(), but then my_struct[i] ?? I would expect craters[i] instead. Another tip is to use a good debugger, you will find the problem in no time
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      1. PODifferent results calculating the average of double variables contained in a vector of structs by altering code formatting?
      1. USRolle
    3. COon another note, your "edit" seems totally unrelated to your first problem and doesnt seem to have anything to do with opencv. probably out of array bounds or similar
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      1. PODifferent results calculating the average of double variables contained in a vector of structs by altering code formatting?
      1. USRolle
 

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