Thanks !
So I changed the following line to include the torch.cuda.synchronize()before and after my function call:
speed_pytorch = np.array(timeit.repeat("torch.cuda.synchronize(); _func(xc, yc, sigmac, bc); torch.cuda.synchronize()", setup='gc.enable();', globals=globals(), repeat=100, number=1))

Here is the new output:
[0.09497609 0.0437831  0.04378436 0.04377997 0.04379042 0.04376097
 0.043768   0.04377071 0.04379098 0.04375806 0.0437383  0.04377674
 0.04379167 0.0437904  0.04375295 0.04374592 0.04381776 0.0440657
 0.04388161 0.04380486 0.04377719 0.04378537 0.04378086 0.04378364
 0.0437904  0.04376343 0.04379515 0.04380947 0.04377766 0.04377795
 0.04378235 0.0438005  0.04378827 0.0437455  0.04377471 0.04377941
 0.04375791 0.04373778 0.04379254 0.04377629 0.0437417  0.04372696
 0.04373221 0.04376795 0.04374417 0.04375209 0.04375083 0.04375326
 0.04374925 0.04375092 0.0438331  0.04380208 0.04376031 0.04374788
 0.04377659 0.04379657 0.04376828 0.04375811 0.0437649  0.04374111
 0.04378433 0.04379105 0.04379046 0.04375545 0.04374755 0.04376093
 0.04376668 0.04376569 0.04375325 0.04378189 0.04379228 0.04373931
 0.04377322 0.04377844 0.0437788  0.04377469 0.04376213 0.04377392
 0.04377192 0.04376317 0.04376967 0.04377655 0.04375631 0.04374702
 0.04378022 0.04380029 0.04377499 0.04374525 0.04377704 0.04376704
 0.0437587  0.04374709 0.04377755 0.04374888 0.04374979 0.04385973
 0.04406279 0.043799   0.04375602 0.04374366]

Mystery solved !
Thanks