Unexpected NaN Results When Performing Calculations with `float` in C
I'm reviewing some code and I'm working with an scenario with unexpected `NaN` results in my calculations when using `float` in C. I'm attempting to compute some statistical functions, such as mean and standard deviation, based on an input array of floats. However, when I perform the calculations, I sometimes get `NaN` values where I expect valid numbers. Here’s a snippet of the code that illustrates the question: ```c #include <stdio.h> #include <math.h> void calculate_stats(float data[], int n, float *mean, float *std_dev) { float sum = 0.0; for (int i = 0; i < n; i++) { sum += data[i]; } *mean = sum / n; float variance_sum = 0.0; for (int i = 0; i < n; i++) { variance_sum += pow(data[i] - *mean, 2); } *std_dev = sqrt(variance_sum / n); } int main() { float values[] = {1.2, 2.3, 3.4, 4.5, 5.6}; float mean, std_dev; calculate_stats(values, 5, &mean, &std_dev); printf("Mean: %f, Standard Deviation: %f\n", mean, std_dev); return 0; } ``` Despite using valid input values, I'm intermittently working with a situation where `std_dev` becomes `NaN`. I’ve double-checked the division by zero, and it seems that all calculations occur on valid numbers. Additionally, I noticed that if I change the values to larger ones (e.g., multiplying them by 1e10), I can consistently reproduce the `NaN` scenario. It seems like an overflow or precision scenario, but I’m not sure how to handle it correctly. I tried using `double` instead of `float`, which mitigated the question somewhat, but I want to keep my calculations in `float` for performance reasons. Is there a recommended way to prevent `NaN` results in these calculations while still using `float`, or should I be using an alternative approach or data type? Any help or insights would be greatly appreciated! Is this even possible? The project is a CLI tool built with C. Any feedback is welcome!