Add gammalib::compare() function (#3552)

Jürgen Knödlseder
1 parent 6afd90f2
Showing 7 changed files with 72 additions and 4 deletions
ChangeLog
NEWS
doc/source/admin/release_history/2.0.rst
include/GTools.hpp
pyext/GTools.i
src/support/GTools.cpp
test/test_GSupport.cpp
@@ -3,6 +3,7 @@
         * Version 2.0.0 released
         ========================
+        Add gammalib::compare() function (#3552)
         Add DRI constructor to GCOMObservation class.
         Add member access methods to GCOMDri class.
         Implement ToF correction for COMPTEL EVP version 2 datasets (#3549)
@@ -80,6 +80,7 @@ The following methods have been added:
 - GCOMDri::num_used_superpackets()
 - GCOMDri::num_skipped_superpackets()
 - gammalib::tmpnam()
+- gammalib::compare()
 The following methods have been removed:
 - none
@@ -209,6 +210,9 @@ Added GSkyRegionRect class to implement a rectangular region on the sky (#3248).
 13. Support module
 ------------------
+Added gammalib::compare() function to compare two floating point numbers with a
+relative tolerance (#3552).
+
 Added gammalib::tmpnam() function to return a temporary file name, in replacement
 of the deprecated str::tmpnam() function (#3324).
@@ -29,6 +29,8 @@ Bug fixes
 Improvements
 ------------
+* [`3552 <https://cta-redmine.irap.omp.eu/issues/3552>`_] -
+  Add ``gammalib::compare()`` function
 * Add DRI constructor to ``GCOMObservation`` class
 * Add member access methods to ``GCOMDri`` class
 * [`3549 <https://cta-redmine.irap.omp.eu/issues/3549>`_] -
 /***************************************************************************
  *                       GTools.hpp - GammaLib tools                       *
  * ----------------------------------------------------------------------- *
- *  copyright (C) 2008-2020 by Juergen Knoedlseder                         *
+ *  copyright (C) 2008-2021 by Juergen Knoedlseder                         *
  * ----------------------------------------------------------------------- *
  *                                                                         *
  *  This program is free software: you can redistribute it and/or modify   *
@@ -151,6 +151,9 @@ namespace gammalib {
                                            const double& sindist,
                                            const double& roi,
                                            const double& cosroi);
+    bool                     compare(const double& a,
+                                     const double& b,
+                                     const double& tol);
 }
 /***************************************************************************
  *                        GTools.i - GammaLib tools                        *
  * ----------------------------------------------------------------------- *
- *  copyright (C) 2008-2020 by Juergen Knoedlseder                         *
+ *  copyright (C) 2008-2021 by Juergen Knoedlseder                         *
  * ----------------------------------------------------------------------- *
  *                                                                         *
  *  This program is free software: you can redistribute it and/or modify   *
@@ -106,4 +106,7 @@ namespace gammalib {
                                            const double& sindist,
                                            const double& roi,
                                            const double& cosroi);
+    bool                     compare(const double& a,
+                                     const double& b,
+                                     const double& tol);
 }
 /***************************************************************************
  *                       GTools.cpp - GammaLib tools                       *
  * ----------------------------------------------------------------------- *
- *  copyright (C) 2008-2020 by Juergen Knoedlseder                         *
+ *  copyright (C) 2008-2021 by Juergen Knoedlseder                         *
  * ----------------------------------------------------------------------- *
  *                                                                         *
  *  This program is free software: you can redistribute it and/or modify   *
@@ -1979,3 +1979,49 @@ double gammalib::roi_arclength(const double&amp; rad,     const double&amp; dist,
     // Return arclength
     return arclength;
 }
+
+
+/***********************************************************************//**
+ * @brief Compare two floating point values with tolerance
+ *
+ * @param[in] a First floating point value.
+ * @param[in] b Second floating point value.
+ * @param[in] tol Relative tolerance.
+ * @return True if both floating point values are identical within
+ *         the tolerance.
+ *
+ * This method tests whether @p a is identical to @p b within a given
+ * relative tolerance @p tol. The test verifies whether
+ *
+ * \f[|a - b| \le |a \times tol|\f]
+ *
+ * for \f$a \ne 0\f$ or whether
+ *
+ * \f[|a - b| \le |b \times tol|\f]
+ *
+ * for \f$b \ne 0\f$. If both \f$a = 0\f$ and \f$b = 0\f$ the method
+ * returns true.
+ ***************************************************************************/
+bool gammalib::compare(const double& a, const double& b, const double& tol)
+{
+    // Initialise identity
+    bool identity = false;
+
+    // Case A: a is not zero
+    if (a != 0.0) {
+        identity = std::abs(a - b) <= std::abs(a * tol);
+    }
+
+    // Case B: b is not zero
+    else if (b != 0.0) {
+        identity = std::abs(a - b) <= std::abs(b * tol);
+    }
+
+    // Case C: a and b are zero
+    else {
+        identity = true;
+    }
+
+    // Return identity
+    return identity;
+}
 /***************************************************************************
  *                 test_GSupport.cpp - test support module                 *
  * ----------------------------------------------------------------------- *
- *  copyright (C) 2010-2020 by Juergen Knoedlseder                         *
+ *  copyright (C) 2010-2021 by Juergen Knoedlseder                         *
  * ----------------------------------------------------------------------- *
  *                                                                         *
  *  This program is free software: you can redistribute it and/or modify   *
@@ -147,6 +147,15 @@ void TestGSupport::test_tools(void)
     test_assert(!gammalib::contains(strings, "b"), "\"b\" not in vector");
     test_assert(!gammalib::contains(strings, "isavector"), "\"isavector\" not in vector");
+    // Test compare method
+    test_assert(gammalib::compare(261.0, 260.999999, 1.0e-8),   "Compare positive floats for tol=1e-8");
+    test_assert(!gammalib::compare(261.0, 260.999999, 1.0e-9), "Compare positive floats for tol=1e-9");
+    test_assert(gammalib::compare(-261.0, -260.999999, 1.0e-8),   "Compare negative floats for tol=1e-8");
+    test_assert(!gammalib::compare(-261.0, -260.999999, 1.0e-9), "Compare negative floats for tol=1e-9");
+    test_assert(gammalib::compare(0.0, 0.0000001, 1.0),   "Compare near zero floats for tol=1.0");
+    test_assert(!gammalib::compare(0.0, 0.0000001, 0.1), "Compare near zero floats for tol=0.1");
+    test_assert(gammalib::compare(0.0, 0.0, 1.0e-10),   "Compare zero floats for tol=1e-10");
+
     // Return
     return;
 }