pow() function call on ARM core

Kiung Chung Wong

Other Parts Discussed in Thread: OMAPL138

Hi,

I am using OMAP L138.

In our application, we have an algorithm that needs to call pow() function. There are ~ 1024 points we need to convert from dBm to watt, it takes ~ 40 ms in total.

double power_watt[i] = pow(10,(power_dBm[i]-30.0)/10.0);

My understading is that ARM has no FPU, so the pow() function (from standard library) is implemented in software.

Any suggestion to make pow() function faster ?

There is a coprocessor CP15 in ARM, not sure can that help ?

Any suggestion will be great ?

rgds,

kc Wong

over 8 years ago

0 Titusrathinaraj Stalin over 8 years ago

TI__Guru** 116100 points

Hi,
You can use DSP core for mathematical operations and its good that you are having OMAPL138 which has ARM+DSP core.
software-dl.ti.com/.../index_FDS.html

powsp() and powdp()

As far as I know, generally we would use CP15 for power saving mode (TCM memory).

0 Kiung Chung Wong over 8 years ago in reply to Titusrathinaraj Stalin

Prodigy 160 points

Hi Titus S.,Thanks for suggestion.
Besides running in DSP, any other suggestion as the DSP is currently dedicated to other tasks ?
rgds,kc Wong

0 Titusrathinaraj Stalin over 8 years ago in reply to Kiung Chung Wong

TI__Guru** 116100 points

Hi,
What is your current CPU operating frequency ?
Try to set CPU freq to maximum (456Mhz for OMAPL13x/C674x devices)
Where is your code reside at ?
Try to have your code in internal RAM(L1/L2/Shared RAM(L3)), it could be faster.

0 Kiung Chung Wong over 8 years ago in reply to Titusrathinaraj Stalin

Prodigy 160 points

Hi Titus S.,
If I remember correctly, it should be 300MHz. As our product is powered through USB, power consumption is a concern, don't think we can set the CPU freq to maximum.
The code should be resided at the external RAM, the DDR2.
I am using the GCC tool chain from Wind River.
Probably, I need to check with Wind River how to make the pow() function call running in internal RAM.
rgds,kc Wong

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pow() function call on ARM core