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POImproving a maths function class for speed c++
 

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  1. POImproving a maths function class for speed c++
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    <p>I wrote some maths functions for use within my program, they are going to get very heavy use. I would like to offer the code up to see if a) there are logic improvements to made and b) if there is a better way of doing any of this. Its a header file which is included where needed. </p> <p>I'm not compiling for c++11 so please bare that in mind. - I'm also aware that the rootDouble for negative numbers is not mathematically correct. </p> <p>I think the first thing which may come up is converting the vector inputs to pass by reference, comments around that are welcome.</p> <p>In terms of me accepting an answer, i'd like to know what and how these functions could be improved for speed.</p> <p>++ I've posted this rather quickly, hope I didn't leave any embarrassing errors inside!</p> <pre><code>#ifndef MATHSFUNCTIONS_H_ #define MATHSFUNCTIONS_H_ #include &lt;algorithm&gt; #include &lt;vector&gt; #include &lt;numeric&gt; #include &lt;cmath&gt; class MathsFunctions { public: MathsFunctions(); virtual ~MathsFunctions(); inline static double squareDouble(double input) { return input * input; } inline static double rootDouble(double input) { if (input == 0.0) { return 0.0; } else if ( input &lt; 0.0) { input = flipDouble(input); input = sqrt(input); return flipDouble(input); } return sqrt(input); } inline static double flipDouble(double input) { return input * -1; } inline static double rangeInVec(std::vector&lt;double&gt; inputs) { return maxInVec(inputs) - minInVec(inputs); } inline static double stdDevInVec(std::vector&lt;double&gt; inputs) { if (inputs.size() &lt; 2) {return 0.0;} double mean = meanInVec(inputs); double sq_sum = std::inner_product(inputs.begin(), inputs.end(), inputs.begin(), 0.0); return std::sqrt(sq_sum / inputs.size() - mean * mean); } inline static double meanInVec(std::vector&lt;double&gt; inputs) { double sum = std::accumulate(inputs.begin(), inputs.end(), 0.0); return sum / inputs.size(); } inline static double sumOfVec(std::vector&lt;double&gt; inputs) { double total = 0.0; for (unsigned int var = 0; var &lt; inputs.size(); ++var) { total += inputs[var]; } return total; } inline static double maxInVec(std::vector&lt;double&gt; inputs) { bool first = true; double max; for (unsigned int var = 0; var &lt; inputs.size(); ++var) { if (first) { max = inputs[var]; first = false; } else { if (inputs[var] &gt; max) { max = inputs[var]; } } } return max; } inline static double minInVec(std::vector&lt;double&gt; inputs) { bool first = true; double min; for (unsigned int var = 0; var &lt; inputs.size(); ++var) { if (first) { min = inputs[var]; first = false; } else { if (inputs[var] &lt; min) { min = inputs[var]; } } } return min; } inline static std::vector&lt;double&gt; weightValueVector(std::vector&lt;double&gt; inputs,std::vector&lt;double&gt; weights) { std::vector&lt;double&gt; results; for (unsigned x = 0; x &lt; inputs.size(); ++x) { results.push_back(inputs[x] * weights[x]); } return results; } }; #endif /* MATHSFUNCTIONS_H_ */ </code></pre>
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    1. COany specific question? it seems to be a code review
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      1. POImproving a maths function class for speed c++
      1. USZac Wrangler
    2. COYeah it is I guess, but the main question is are there any places I can improve for speed
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      1. USjoeButler
    3. COYou don't need to write max,sum,min functions, STL algorithms provided them already
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      1. USbillz
 

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