diff carfac/carfac_common.cc @ 610:01986636257a

Second check-in of Alex Brandmeyer's C++ implementation of CARFAC. Addressed style issues and completed implementation of remaining functions. Still needs proper testing of the output stages against the MATLAB version, and runtime functions need improvements in efficiency.

--- a/carfac/carfac_common.cc	Mon May 13 22:51:15 2013 +0000
+++ b/carfac/carfac_common.cc	Thu May 16 17:33:23 2013 +0000
@@ -22,39 +22,22 @@
 
 #include "carfac_common.h"
 
-//Auditory filter nominal Equivalent Rectangular Bandwidth
-//Ref: Glasberg and Moore: Hearing Research, 47 (1990), 103-138
+// Auditory filter nominal Equivalent Rectangular Bandwidth
+// Ref: Glasberg and Moore: Hearing Research, 47 (1990), 103-138
 FPType ERBHz (FPType cf_hz, FPType erb_break_freq, FPType erb_q) {
-  
   FPType erb;
   erb = (erb_break_freq + cf_hz) / erb_q;
   return erb;
 }
 
-//An IHC-like sigmoidal detection nonlinearity for the CARFAC.
-//Resulting conductance is in about [0...1.3405]
-FPType CARFACDetect (FPType x) {
-  
-  FPType conductance, z;
+FloatArray CARFACDetect (FloatArray x) {
+  FloatArray conductance, z, set;
   FPType a = 0.175;
-  //offset of low-end tail into neg x territory
-  //this parameter is adjusted for the book, to make the 20% DC response
-  //threshold at 0.1
+  // This offsets the low-end tail into negative x territory.
+  // The parameter is adjusted for the book, to make the 20% DC response
+  // threshold at 0.1.
   z  = x + a;
-  conductance = pow(z,3) / (pow(z,3) + pow(z,2) + 0.1);
-  //zero is the final answer for many points:
-  return conductance;
-}
-
-FloatArray CARFACDetect (FloatArray x) {
-  
-  FloatArray conductance, z;
-  FPType a = 0.175;
-  //offset of low-end tail into neg x territory
-  //this parameter is adjusted for the book, to make the 20% DC response
-  //threshold at 0.1
-  z  = x + a;
-  conductance = (z * z * z) / ((z * z * z) + (z * z) + 0.1);
-  //zero is the final answer for many points:
+  // Zero is the final answer for many points.
+  conductance = (z < 0).select(0.0, (z * z * z) / (z * z * z + z * z + 0.1));
   return conductance;
 }
\ No newline at end of file