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changeset 19935:554aaaf99644

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Fix return phase of acosh to match Matlab (bug #44286). * NEWS: Announce change. * mappers.cc (Facosh): Add BIST tests for new behavior. * lo-mappers.cc: Re-write expression sqrt (x*x -1.0) as sqrt (x + 1.0) * sqrt (x - 1.0) which gets phase correct if x is complex.
author Rik <rik@octave.org>
date Tue, 17 Feb 2015 11:07:01 -0800
parents 17a7e9f26e50
children 9861618b4c5f
files NEWS libinterp/corefcn/mappers.cc liboctave/numeric/lo-mappers.cc
diffstat 3 files changed, 18 insertions(+), 2 deletions(-) [+]
line wrap: on
line diff
--- a/NEWS
+++ b/NEWS
@@ -87,6 +87,10 @@
     limit from above is taken.  This criteria is consistent with several other
     numerical analysis software packages.
 
+ ** The hyperbolic function acosh now returns values with a phase in the range
+    [-pi/2, +pi/2].  Previously Octave returned values in the range [0, pi].
+    This is consistent with several other numerical analysis software packages.
+
  ** strfind changes when using empty pattern ("") for Matlab compatibility
 
     strfind now returns an empty array when the pattern itself is empty.
--- a/libinterp/corefcn/mappers.cc
+++ b/libinterp/corefcn/mappers.cc
@@ -155,10 +155,22 @@
 %! assert (acosh (x), v, sqrt (eps));
 
 %!test
+%! re = 2.99822295029797;
+%! im = pi/2;
+%! assert (acosh (10i), re + i*im);
+%! assert (acosh (-10i), re - i*im);
+
+%!test
 %! x = single ([1, 0, -1, 0]);
 %! v = single ([0, pi/2*i, pi*i, pi/2*i]);
 %! assert (acosh (x), v, sqrt (eps ("single")));
 
+%!test
+%! re = single (2.99822295029797);
+%! im = single (pi/2);
+%! assert (acosh (single (10i)), re + i*im, 5*eps ("single"));
+%! assert (acosh (single (-10i)), re - i*im, 5*eps ("single"));
+
 %!error acosh ()
 %!error acosh (1, 2)
 */
--- a/liboctave/numeric/lo-mappers.cc
+++ b/liboctave/numeric/lo-mappers.cc
@@ -197,7 +197,7 @@
 Complex
 acosh (const Complex& x)
 {
-  return log (x + sqrt (x*x - 1.0));
+  return log (x + sqrt (x + 1.0) * sqrt (x - 1.0));
 }
 
 Complex
@@ -434,7 +434,7 @@
 FloatComplex
 acosh (const FloatComplex& x)
 {
-  return log (x + sqrt (x*x - static_cast<float>(1.0)));
+  return log (x + sqrt (x + 1.0f) * sqrt (x - 1.0f));
 }
 
 FloatComplex