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How optimize speed of vector initialization? RRS feed

  • Question

  • I am using boost/multiprecision/cpp_int.hpp for arbitrary length integers computing.

    Now I am testing simplest algorithm for multiplication: wiki/Multiplication_algorithm#Long_multiplication

    My algorithm tested with Visual 2019 Release is several times slower than boost algorithm, but when I change vecctor do stack constant arrays is faster than Boost for small numbers. Most time is spent in:

    vector<SingleDigit> standard_multiply(const vector<SingleDigit>&a, const vector<SingleDigit>&b)
    {
    	int p = a.size();
    	int q = b.size();
    	vector<SingleDigit> product;
    	product.resize(p + q);
    
    In product.resize or
    vector<SingleDigit> product(p+q);
    Boost sources is more complicated but faster is allocated number.

    Monday, November 4, 2019 11:33 PM

All replies

  • Hi,

    Thank you for posting here.

    This forum is about c++ development. According to your issue , I suggest you should ask it in a boost newsgroup or forum. And this thread will be moved to Off-Topic Posts.

    Best Regards,

    Suarez Zhou


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    Tuesday, November 5, 2019 6:03 AM
  • Tuesday, November 5, 2019 7:05 AM