Hi i'm developing and image processing application on the Nxp imx7 and I want to compare performance of NEON instrutions vs pure c.
c: a,b,c are float32. Take 11ms to run
for(int pixIndex = 0;pixIndex<(640*480);pixIndex++)
a[pixIndex] = (a[pixIndex] * b[pixIndex]) + c[pixIndex];
NEON: Take 10ms to run
for(int pixIndex = 0;pixIndex<(640*480)/2;pixIndex++)
float32x2_t dVect1, dVect2,dVect3;
dVect1 = vld1_f32(a);
dVect2 = vld1_f32(b);
dVect3 = vld1_f32(c);
dVect1 = vmla_f32(dVect3,dVect1,dVect2);
Why NEON is only 1ms faster than c ? Do I miss something here ?
Possibly hardware floating point is turned on by default in the toolchain.
And this small difference may be caused with methods of passing parameters.
I mean in first case you pass the parameters for multiplying and for adding functions but in second case only once for MLA.