Fastest way to read numerical values from text file in C++ (double in this case)

Question

Currently, my code is simply this:

void ReadFile(double Cst[][1000], char* FileName, int height)

FILE* ifp;
double value;
int nRead = 0;
int mRead = 0;

//o         


        

Answer 1

atof is probably much faster, it doesn't have to process the format string.

If you don't need to support all 1001 recognized input formats (with and without exponents, etc) then a custom function may be faster yet. If atof is still too slow for you, say so and I can clean up the code I use (it's not really suitable for public posting at the moment).

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I just remembered the problem with atof -- it doesn't tell you where the number ended, so reading several numbers in sequence is difficult. strtod is better in that regard.