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  #1  
Old 11-Jun-2004, 20:40
BobbyMurcerFan BobbyMurcerFan is offline
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When to Use Double vs Float?


Is there a rule of thumb for when to use a double vs. a float? I imagine it has to do with size and precision, but I'm not sure how make an intelligent choice between the two.

Also, it seems some fractions are easier to represent in binary than others. So I don't think it's just a matter of how many decimal places but also what actual value you are trying to store.

Nonetheless, I will be representing numbers up to in the tens of thousands with up to 3 decimal places, i.e. nn,nnn.nnn

Float uses 4 bytes and double 8 bytes with my compiler.

Thanks!
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Old 12-Jun-2004, 00:18
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tay tay is offline
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float with precision total is 7 digit.
double with precision total is 15 digit.

If you want to control the decimal or precision, you can use:

Code:
setprecision ( 2 ) // only 2 decimal , e.g 12.22 setprecision ( 3 ) // 12.333

but you must #include <iomanip>

For your case, you just use 10,000 already 5 digit, and I not sure how many decimal you want. If 2 still can use float, if 3 must use double.

In case your decimal is 2, your digit may be more than 8, so you better use double.
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Old 13-Jun-2004, 14:00
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