commit 07f208fd6d7fa06571e5dceb072c2f270d148193
author Sameer Agarwal <sameeragarwal@google.com> Wed May 22 09:08:06 2013 -0700
committer Sameer Agarwal <sameeragarwal@google.com> Wed May 22 12:58:58 2013 -0700
tree 154303210de1c2d15832922d32d8ca34c902ae61
parent df0125666af1bf37878b8e5cab5c6479d1b90842

Speed up corrector.cc

Remove the Eigen temporary by revealing the columnwise nature
of the computation. This also allows us to get rid of the
special case for nrow = 1.

On problem-356-226730-pre.txt with -robustify evaluation times
change from:

Before:
  Residual Evaluations                  1.015
  Jacobian Evaluations                 18.313

After:
  Residual Evaluations                  1.005
  Jacobian Evaluations                  8.382

To give a sense of the overhead reduction, compare these numbers
when loss functions are disabled.

  Residual Evaluations                  0.955
  Jacobian Evaluations                  7.772

So, this is a 17.5x speedup!

The one dimensional specialization was motivated by denoising.cc.
The evaluation times there are essentially unchanged.

Before:
  Residual Evaluations                  2.774
  Jacobian Evaluations                 20.178

After:
  Residual Evaluations                  2.588
  Jacobian Evaluations                 19.781

Change-Id: Ic0efbaed75fe4489635039f17189ae24b97802c8

internal/ceres/corrector.h

diff --git a/internal/ceres/corrector.h b/internal/ceres/corrector.h
index 9914641..2137221 100644
--- a/internal/ceres/corrector.h
+++ b/internal/ceres/corrector.h
@@ -66,7 +66,7 @@
   explicit Corrector(double sq_norm, const double rho[3]);
 
   // residuals *= sqrt(rho[1]) / (1 - alpha)
-  void CorrectResiduals(int nrow, double* residuals);
+  void CorrectResiduals(int num_rows, double* residuals);
 
   // jacobian = sqrt(rho[1]) * jacobian -
   // sqrt(rho[1]) * alpha / sq_norm * residuals residuals' * jacobian.
@@ -74,8 +74,10 @@
   // The method assumes that the jacobian has row-major storage. It is
   // the caller's responsibility to ensure that the pointer to
   // jacobian is not null.
-  void CorrectJacobian(int nrow, int ncol,
-                       double* residuals, double* jacobian);
+  void CorrectJacobian(int num_rows,
+                       int num_cols,
+                       double* residuals,
+                       double* jacobian);
 
  private:
   double sqrt_rho1_;