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by owenversteeg
2663 days ago
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As far as I know, RNGs on computers use the first few digits, not the last. The reason why, and the problem with using the last, is that your laptop probably measures the voltage of a thermistor coupled to a resistor using an ADC. So you're dependent on an ADC (analog-digital converter) chip that takes voltage and gives you a digital signal. If you have a 12-bit ADC (commonly used to measure voltage), that means you get 2^12=4096 bins. So if your maximum and minimum voltage from the thermistor perfectly line up with the ADC's range, and your temperature can vary from -50 to +50C, then you get increments of 0.025 degrees C. It's pretty easy to see that the last few digits are very much not random, and using them would not work! Mildly related and fun: https://electronics.stackexchange.com/questions/274606/whats... (if you spend a bajillion dollars to set up a 32-bit ADC with everything needed, and have a 100C range, you get increments of 100/2^32 = 2.33e-8, now that's precise! This probably would be a bad way to get randomness for about 20 other reasons, though) |
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