LAUNCHXL-F28379D: Sum Arithmetic in F28379D

Quoc Ngo

Part Number: LAUNCHXL-F28379D

Dear Ti expert,

I have little confuse about sum arithmetic on F28379 mcu. when i test simple calculation float test = 0.5f + 0.7f, the result is 1.20000005. I Don't know why the result is 1.20000005 not 1.2. i have attached a pictures for the problem. I would appreciate if you can help.

Best Regards

Quoc Ngo

over 5 years ago

0 Richard Poley over 5 years ago

TI__Mastermind 27200 points

Quoc Ngo,

This is the resolution limit of floating point. In single precision the mantissa has 23 bits. You cannot represent 1.2 exactly - in hex you can have either:

0x3F99999A which is 1.20000005, or

0x3F999999 which is 1.19999993

Regards,

Richard

0 Quoc Ngo over 5 years ago in reply to Richard Poley

Prodigy 70 points

Hello Richard,

Thank you for your quickly response.

Best Regards

Quoc Ngo

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LAUNCHXL-F28379D: Sum Arithmetic in F28379D