# HG changeset patch
# User Jaroslav Hajek <address@hidden>
# Date 1221643678 -7200
# Node ID 87c7705d0be8c4268bddd6e51c24f84dc3721aef
# Parent  fc45357bf50ccdb48fceb36ef92db2c5e19dc671
simplify expm inverse permutations

diff --git a/liboctave/CMatrix.cc b/liboctave/CMatrix.cc
--- a/liboctave/CMatrix.cc
+++ b/liboctave/CMatrix.cc
@@ -3036,8 +3036,8 @@
   for (octave_idx_type i = 0; i < nc; i++)
     iperm(i) = i;  // initialize to identity permutation
 
-  // leading permutations in forward order
-  for (octave_idx_type i = 0; i < (ilo-1); i++)
+  // trailing permutations must be done in reverse order
+  for (octave_idx_type i = nc - 1; i >= ihi; i--)
     {
       octave_idx_type swapidx = static_cast<octave_idx_type> (dpermute(i)) - 1;
       octave_idx_type tmp = iperm(i);
@@ -3045,25 +3045,8 @@
       iperm(swapidx) = tmp;
     }
 
-  // construct inverse balancing permutation vector
-  Array<octave_idx_type> invpvec (nc);
-  for (octave_idx_type i = 0; i < nc; i++)
-    invpvec(iperm(i)) = i;     // Thanks to R. A. Lippert for this method
-
-  OCTAVE_QUIT;
-
-  ComplexMatrix tmpMat = retval;
-  for (octave_idx_type i = 0; i < nc; i++)
-    for (octave_idx_type j = 0; j < nc; j++)
-      retval(i,j) = tmpMat(invpvec(i),invpvec(j));
-
-  OCTAVE_QUIT;
-
-  for (octave_idx_type i = 0; i < nc; i++)
-    iperm(i) = i;  // initialize to identity permutation
-
-  // trailing permutations must be done in reverse order
-  for (octave_idx_type i = nc - 1; i >= ihi; i--)
+  // leading permutations in forward order
+  for (octave_idx_type i = 0; i < (ilo-1); i++)
     {
       octave_idx_type swapidx = static_cast<octave_idx_type> (dpermute(i)) - 1;
       octave_idx_type tmp = iperm(i);
@@ -3072,17 +3055,19 @@
     }
 
   // construct inverse balancing permutation vector
+  Array<octave_idx_type> invpvec (nc);
   for (octave_idx_type i = 0; i < nc; i++)
     invpvec(iperm(i)) = i;     // Thanks to R. A. Lippert for this method
 
   OCTAVE_QUIT;
 
-  tmpMat = retval;
+  ComplexMatrix tmpMat = retval;
   for (octave_idx_type i = 0; i < nc; i++)
     for (octave_idx_type j = 0; j < nc; j++)
       retval(i,j) = tmpMat(invpvec(i),invpvec(j));
 
   // Reverse preconditioning step 1: fix trace normalization.
+
 
   return exp (trshift) * retval;
 }
diff --git a/liboctave/ChangeLog b/liboctave/ChangeLog
--- a/liboctave/ChangeLog
+++ b/liboctave/ChangeLog
@@ -0,0 +1,5 @@
+2008-09-12  Marco Caliari  <address@hidden>
+
+	* dMatrix.cc (Matrix::expm): Simplify reverse permutation.
+	* CMatrix.cc (ComplexMatrix::expm): Likewise.
+
diff --git a/liboctave/dMatrix.cc b/liboctave/dMatrix.cc
--- a/liboctave/dMatrix.cc
+++ b/liboctave/dMatrix.cc
@@ -2668,12 +2668,21 @@
   for (octave_idx_type i = 0; i < nc; i++)
     iperm(i) = i;  // identity permutation
 
+  // trailing permutations must be done in reverse order
+  for (octave_idx_type i = nc - 1; i >= ihi; i--)
+    {
+      octave_idx_type swapidx = static_cast<octave_idx_type> (dpermute(i)) - 1;
+      octave_idx_type tmp = iperm(i);
+      iperm(i) = iperm(swapidx);
+      iperm(swapidx) = tmp;
+    }
+
   // leading permutations in forward order
   for (octave_idx_type i = 0; i < (ilo-1); i++)
     {
       octave_idx_type swapidx = static_cast<octave_idx_type> (dpermute(i)) - 1;
       octave_idx_type tmp = iperm(i);
-      iperm(i) = iperm (swapidx);
+      iperm(i) = iperm(swapidx);
       iperm(swapidx) = tmp;
     }
 
@@ -2689,32 +2698,8 @@
     for (octave_idx_type j = 0; j < nc; j++)
       retval(i,j) = tmpMat(invpvec(i),invpvec(j));
 
-  OCTAVE_QUIT;
+  // Reverse preconditioning step 1: fix trace normalization.
 
-  for (octave_idx_type i = 0; i < nc; i++)
-    iperm(i) = i;  // identity permutation
-
-  // trailing permutations must be done in reverse order
-  for (octave_idx_type i = nc - 1; i >= ihi; i--)
-    {
-      octave_idx_type swapidx = static_cast<octave_idx_type> (dpermute(i)) - 1;
-      octave_idx_type tmp = iperm(i);
-      iperm(i) = iperm(swapidx);
-      iperm(swapidx) = tmp;
-    }
-
-  // construct inverse balancing permutation vector
-  for (octave_idx_type i = 0; i < nc; i++)
-    invpvec(iperm(i)) = i;     // Thanks to R. A. Lippert for this method
-
-  OCTAVE_QUIT;
- 
-  tmpMat = retval;
-  for (octave_idx_type i = 0; i < nc; i++)
-    for (octave_idx_type j = 0; j < nc; j++)
-      retval(i,j) = tmpMat(invpvec(i),invpvec(j));
-
-  // Reverse preconditioning step 1: fix trace normalization.
   
   if (trshift > 0.0)
     retval = exp (trshift) * retval;