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IAR : 32 bits SP is not 64 bits DP !

Question asked by bonelli on Nov 26, 2014
Latest reply on Nov 26, 2014 by fm
Reading http://www.iar.com/Global/Resources/Developers_Toolbox/C_Cplusplus_Programming/Improve_performance_of_digital_signal_processing_with_IAR_Embedded_Workbench_for_ARM.pdf
page 3 :

arm_sqrt_f32 : 52 cycles
sqrt : 752 cycles

The cycles count are good. BUT sqrt works on 64 bits double precision floating point number.

Try use sqrtf instead : armcc will use VSQRT instruction, during 14 cycles (25-28 cycles including function call) => sqrtf is 2 time faster than the DSP iterative algorithm.

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