# HG changeset patch
# User jwe
# Date 1194366373 0
# Node ID 2c5b14c60c6c6e751ab7d6430a0c5bfc70527123
# Parent  28607462901fccf472a909ac14f2cf8ae901ad75
[project @ 2007-11-06 16:26:13 by jwe]

diff --git a/liboctave/MArray-defs.h b/liboctave/MArray-defs.h
--- a/liboctave/MArray-defs.h
+++ b/liboctave/MArray-defs.h
@@ -358,13 +358,25 @@
 	  /* Frobenius norm.  */ \
 	  retval = 0; \
  \
+          /* precondition */ \
+          double inf_norm = 0.; \
 	  for (octave_idx_type i = 0; i < len; i++) \
 	    { \
-	      double d_abs = std::abs (d[i]); \
+              double d_abs = std::abs (d[i]); \
+              if (d_abs > inf_norm) \
+                inf_norm = d_abs; \
+            } \
+          inf_norm = (inf_norm == octave_Inf || inf_norm == 0. ? 1.0 : \
+		      inf_norm); \
+          double scale = 1. / inf_norm; \
+\
+	  for (octave_idx_type i = 0; i < len; i++) \
+	    { \
+	      double d_abs = std::abs (d[i]) * scale; \
 	      retval += d_abs * d_abs; \
 	    } \
  \
-	  retval = ::sqrt (retval); \
+	  retval = ::sqrt (retval) * inf_norm; \
 	} \
       else if (p == 2) \
 	F77_FCN (blas_norm, BLAS_NORM) (len, d, 1, retval); \
diff --git a/scripts/ChangeLog b/scripts/ChangeLog
--- a/scripts/ChangeLog
+++ b/scripts/ChangeLog
@@ -1,3 +1,9 @@
+2007-11-06  David Bateman  <dbateman@free.fr>
+
+	* linear-algebra/__norm__.m: Scale frobenius norm by infinity norm
+	to avoid issues of over- and underflow.  From Rolf Fabian
+	<Rolf.Fabian@gmx.de>.
+
 2007-11-02  Olli Saarela  <Olli.Saarela@kcl.fi>
 
 	* time/asctime.m, general/structfun.m: Fix broken @examples in
diff --git a/scripts/linear-algebra/__norm__.m b/scripts/linear-algebra/__norm__.m
--- a/scripts/linear-algebra/__norm__.m
+++ b/scripts/linear-algebra/__norm__.m
@@ -40,11 +40,11 @@
   endif
 
   ## Do we have a vector or matrix as the first argument?
-
   if (ndims(x) == 2 && (rows (x) == 1 || columns (x) == 1))
     if (ischar (p))
       if (strcmp (p, "fro"))
-	retval = sqrt (sum (abs (x) .^ 2));
+        inf_norm = norm (x, "inf")
+	retval = inf_norm .* sqrt (sum (abs (x ./ inf_norm) .^ 2));
       elseif (strcmp (p, "inf"))
         retval = max (abs (x));
       else
@@ -69,7 +69,8 @@
   else
     if (ischar (p))
       if (strcmp (p, "fro"))
-	retval = sqrt (sum (sum (abs (x) .^ 2)));
+        inf_norm = norm (x, "inf")
+	retval = inf_norm .* sqrt (sum (sum (abs (x ./ inf_norm) .^ 2)));
       elseif (strcmp (p, "inf"))
         retval = max (sum (abs (x')));
       else
diff --git a/src/ChangeLog b/src/ChangeLog
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,3 +1,14 @@
+2007-11-06  John W. Eaton  <jwe@octave.org>
+
+	* defun-int.h (DEFINE_FUNX_INSTALLER_FUN3): Don't install function
+	if check_version produces an error.
+
+2007-11-06  David Bateman  <dbateman@free.fr>
+
+	* MArray-def.h (MARRAY_NORM_BODY): Scale frobenius norm by infinity
+	norm to avoid issues of over- and underflow.  From Rolf Fabian
+	<Rolf.Fabian@gmx.de>.
+
 2007-11-05  John W. Eaton  <jwe@octave.org>
 
 	* pt-idx.cc (tree_index_expression::lvalue): Try to do a better
diff --git a/src/defun-int.h b/src/defun-int.h
--- a/src/defun-int.h
+++ b/src/defun-int.h
@@ -95,9 +95,16 @@
   bool \
   fsname ## _ ## cxx_abi (const octave_shlib& shl, bool relative) \
   { \
+    bool retval = true; \
+ \
     check_version (OCTAVE_API_VERSION, name); \
-    install_dld_function (fname, name, shl, doc, false, relative); \
-    return error_state ? false : true; \
+ \
+    if (error_state) \
+      retval = false; \
+    else \
+      install_dld_function (fname, name, shl, doc, false, relative); \
+ \
+    return retval; \
   }
 
 // MAKE_BUILTINS is defined to extract function names and related