How to speed up STM32G474 float number calculation?

[QMa.1]

Hello,

I am new to STM32 MCU and right now using a 170MHz STM32G474 MCU for my project. I did a test today and found out the float number calculation speed of the MCU is quite slow.

It takes 6.3us to finish the calculation in Fig.1. (I set a GPIO pin high before the calculation starts and set it to low after the calculation). ADC_Value[] is integer and the rest variables are float. The speed is just too slow to believe.

 

The clock is set to be 170MHz. Am I missing something in the project setting (shown in Fig2 and Fig3)? Is this the real calculation speed for the MCU?

I know that in TI C2000 DSP, we can include a Scalar Factor Optimizer Library header to speed up the float calculation (SFO_V8.h). Does the STM32 DSP have the similar headers? Thanks.

 

[S.Ma]

If you don't need mantisse, why not stick to fractional binary like Q31, or calculate with pre.multiplied values by 1024? FMAC I guess is an IP to contemplate.

Otherwise, check your project settings, use of FPU vs sw emulated library, compiler optimisatipn mode, etc....

[Tesla DeLorean]

Check the generated code, check it's using float constants

[GLASS · Accepted solution]

Try to change ALL const value to float as said by Tesla...​

For example​ use 0.2f instead of 0.2 (the Last one is a double !)

If the real app work on large buffer of adc value, consider loop unrolling coding optimisa​tion instead of calling Adc_management() for each set of sample.

[MM..1]

-fsingle-precision-constant

[QMa.1]

Thanks for the example. I changed all the numbers to float format and used the -Ofast optimizer in the GCC Compiler Optimization setting. The calculation time length is reduced by 85% -- a much reasonable number. Thanks!

[Piranha]

https://www.brighthub.com/computing/linux/articles/11239/