[mlpack-svn] r13109 - mlpack/trunk/src/mlpack/methods/sparse_coding

[fastlab-svn at coffeetalk-1.cc.gatech.edu]

Author: rcurtin
Date: 2012-06-26 15:16:29 -0400 (Tue, 26 Jun 2012)
New Revision: 13109

Modified:
   mlpack/trunk/src/mlpack/methods/sparse_coding/sparse_coding_impl.hpp
Log:
Avoid a matrix copy for matActiveZ and potentially speed up gradient calculation
by avoiding instantiation of arma::ones<arma::vec> (Armadillo may have already
been smart enough to avoid that anyway).


Modified: mlpack/trunk/src/mlpack/methods/sparse_coding/sparse_coding_impl.hpp
===================================================================
--- mlpack/trunk/src/mlpack/methods/sparse_coding/sparse_coding_impl.hpp	2012-06-26 19:10:40 UTC (rev 13108)
+++ mlpack/trunk/src/mlpack/methods/sparse_coding/sparse_coding_impl.hpp	2012-06-26 19:16:29 UTC (rev 13109)
@@ -153,12 +153,8 @@
 
   // Efficient construction of Z restricted to active atoms.
   arma::mat matActiveZ;
-  if (inactiveAtoms.empty())
+  if (!inactiveAtoms.empty())
   {
-    matActiveZ = codes;
-  }
-  else
-  {
     arma::uvec inactiveAtomsVec =
         arma::conv_to<arma::uvec>::from(inactiveAtoms);
     RemoveRows(codes, inactiveAtomsVec, matActiveZ);
@@ -191,9 +187,22 @@
   //    dualVars(i) = 0;
 
   bool converged = false;
-  arma::mat codesXT = matActiveZ * trans(data);
-  arma::mat codesZT = matActiveZ * trans(matActiveZ);
 
+  // If we have any inactive atoms, we must construct these differently.
+  arma::mat codesXT;
+  arma::mat codesZT;
+
+  if (inactiveAtoms.empty())
+  {
+    codesXT = codes * trans(data);
+    codesZT = codes * trans(codes);
+  }
+  else
+  {
+    codesXT = matActiveZ * trans(data);
+    codesZT = matActiveZ * trans(matActiveZ);
+  }
+
   double improvement;
   for (size_t t = 1; !converged; ++t)
   {
@@ -201,8 +210,8 @@
 
     arma::mat matAInvZXT = solve(A, codesXT);
 
-    arma::vec gradient = -(arma::sum(arma::square(matAInvZXT), 1) -
-        arma::ones<arma::vec>(nActiveAtoms));
+    arma::vec gradient = -arma::sum(arma::square(matAInvZXT), 1);
+    gradient += 1;
 
     arma::mat hessian = -(-2 * (matAInvZXT * trans(matAInvZXT)) % inv(A));