cmcq wrote:
Author: cmcq
Date: Wed Aug 5 14:50:55 2009
New Revision: 4945
Log:
sqrt is faster than log by about five times (or 2.5 times with libimf)
test program:
[...]
energy_pred = ff_dot_productf(energy_pred_fac, prev_pred_error, 4);
- energy_fixed_mean = ff_energyf(fixed_vector, AMR_SUBFRAME_SIZE);
- energy_fixed_mean = 10.0 * log10f(energy_fixed_mean / AMR_SUBFRAME_SIZE);
+ energy_fixed_mean = sqrt(ff_energyf(fixed_vector, AMR_SUBFRAME_SIZE) /
+ AMR_SUBFRAME_SIZE);
- return powf(10.0, 0.05 * (energy_pred + energy_mean[mode] -
- energy_fixed_mean));
+ return powf(10.0, 0.05 * (energy_pred + energy_mean[mode])) /
+ energy_fixed_mean;
If you do
return expf(logf(10.0) * 0.05 * (energy_pred + energy_mean[mode])) /
energy_fixed_mean;
it will be probably faster (logf(10.0)*0.05 will be evaluated at
compile-time).
-Vitor
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