[svn-r20384] Purpose:

    Fixed Bug 2184 - GMQS: h5diff - incorrect calculation code for 
    --use-system-epsilon option

Description:
    Merged from HDF5 1.8 branch r20369.
    Fixed h5diff for --use-system-epsilon option: the calculation changed
    from ( |a - b| / b ) to ( |a - b| ). This was decided for better 
    performance and was corrected only in HDF5 trunk, so 1.8 got updated.
    Also comments for equal_XXX() function were updated correctly. 
    Also help page and RM got updated correctly.
    Also add test cases for testing the differences w/wo the option.

     
Tested:
 jam (linux32-LE), amani (linux64-LE), heiwa (linuxppc64-BE), tejeda (mac32-LE), linew (solaris-BE), Windows (32-LE)

24 files changed, 145 insertions, 125 deletions

diff --git a/tools/h5diff/CMakeLists.txt b/tools/h5diff/CMakeLists.txt
index 48ba8e6..97c3a3c 100644
--- a/tools/h5diff/CMakeLists.txt
+++ b/tools/h5diff/CMakeLists.txt
@@ -45,6 +45,8 @@ IF (BUILD_TESTING)
       h5diff_100.txt
       #h5diff_101.txt
       #h5diff_102.txt
+      #h5diff_103.txt
+      #h5diff_104.txt
       h5diff_11.txt
       h5diff_12.txt
       h5diff_13.txt
@@ -260,6 +262,19 @@ IF (BUILD_TESTING)
         COMMAND    ${CMAKE_COMMAND}
         ARGS       -E copy_if_different ${HDF5_TOOLS_H5DIFF_SOURCE_DIR}/testfiles/h5diff_102w.txt ${PROJECT_BINARY_DIR}/h5diff_102.txt
     )
+    ADD_CUSTOM_COMMAND (
+        TARGET     h5diff
+        POST_BUILD
+        COMMAND    ${CMAKE_COMMAND}
+        ARGS       -E copy_if_different ${HDF5_TOOLS_H5DIFF_SOURCE_DIR}/testfiles/h5diff_103w.txt ${PROJECT_BINARY_DIR}/h5diff_103.txt
+    )
+
+    ADD_CUSTOM_COMMAND (
+        TARGET     h5diff
+        POST_BUILD
+        COMMAND    ${CMAKE_COMMAND}
+        ARGS       -E copy_if_different ${HDF5_TOOLS_H5DIFF_SOURCE_DIR}/testfiles/h5diff_104w.txt ${PROJECT_BINARY_DIR}/h5diff_104.txt
+    )
   ELSE (WIN32 AND NOT CYGWIN)
     ADD_CUSTOM_COMMAND (
         TARGET     h5diff
@@ -274,6 +289,19 @@ IF (BUILD_TESTING)
         COMMAND    ${CMAKE_COMMAND}
         ARGS       -E copy_if_different ${HDF5_TOOLS_H5DIFF_SOURCE_DIR}/testfiles/h5diff_102.txt ${PROJECT_BINARY_DIR}/h5diff_102.txt
     )
+    ADD_CUSTOM_COMMAND (
+        TARGET     h5diff
+        POST_BUILD
+        COMMAND    ${CMAKE_COMMAND}
+        ARGS       -E copy_if_different ${HDF5_TOOLS_H5DIFF_SOURCE_DIR}/testfiles/h5diff_103.txt ${PROJECT_BINARY_DIR}/h5diff_103.txt
+    )
+
+    ADD_CUSTOM_COMMAND (
+        TARGET     h5diff
+        POST_BUILD
+        COMMAND    ${CMAKE_COMMAND}
+        ARGS       -E copy_if_different ${HDF5_TOOLS_H5DIFF_SOURCE_DIR}/testfiles/h5diff_104.txt ${PROJECT_BINARY_DIR}/h5diff_104.txt
+    )
   ENDIF (WIN32 AND NOT CYGWIN)
   
 ##############################################################################
@@ -371,6 +399,10 @@ IF (BUILD_TESTING)
           h5diff_101.out.err
           h5diff_102.out
           h5diff_102.out.err
+          h5diff_103.out
+          h5diff_103.out.err
+          h5diff_104.out
+          h5diff_104.out.err
           h5diff_11.out
           h5diff_11.out.err
           h5diff_12.out
@@ -935,6 +967,13 @@ ADD_H5_TEST (h5diff_101 1 -v ${FILE1} ${FILE1} g1/d1  g1/d2)
 
 ADD_H5_TEST (h5diff_102 1 -v ${FILE1} ${FILE1} g1/fp1 g1/fp2) 
 
+# with --use-system-epsilon for double value. expect less differences  
+ADD_H5_TEST (h5diff_103 1 -v --use-system-epsilon ${FILE1} ${FILE1} g1/d1
+g1/d2) 
+
+# with --use-system-epsilon for float value. expect less differences
+ADD_H5_TEST (h5diff_104 1 -v --use-system-epsilon ${FILE1} ${FILE1} g1/fp1
+g1/fp2)
 
 # not comparable -c flag
 ADD_H5_TEST (h5diff_200 0 ${FILE2} ${FILE2} g2/dset1  g2/dset2) 
diff --git a/tools/h5diff/h5diff_common.c b/tools/h5diff/h5diff_common.c
index da420b0..e0af7f6 100644
--- a/tools/h5diff/h5diff_common.c
+++ b/tools/h5diff/h5diff_common.c
@@ -485,17 +485,11 @@ void usage(void)
  printf("                           number.\n");
  printf("   -p R, --relative=R      Print difference if (|(a-b)/b| > R), R is a positive\n");
  printf("                           number.\n");
- printf("   --use-system-epsilon    Print difference if (|a-b| > EPSILON),\n");
- printf("                           where EPSILON (FLT_EPSILON or FLT_EPSILON) is the\n");
- printf("                           system epsilon value. \n");
- printf("                           If the system epsilon is not defined, use the value\n");
- printf("                           below:\n");
+ printf("   --use-system-epsilon    Print difference if (|a-b| > EPSILON), EPSILON is\n");
+ printf("                           a system epsilon value.\n");
+ printf("                           The system epsilon values are defined as below:\n");
  printf("                               FLT_EPSILON = 1.19209E-07 for float\n");
  printf("                               DBL_EPSILON = 2.22045E-16 for double\n");
- printf("                           -d, -p, and --use-system-epsilon options are used for\n");
- printf("                           comparing floating point values.\n");
- printf("                           By default, strict equality is used. Use -p or -d to\n");
- printf("                           set specific tolerance.\n");
  printf("   --exclude-path \"path\"   Exclude the specified path to an object when\n");
  printf("                           comparing files or groups. If a group is excluded,\n");
  printf("                           all member objects will also be excluded.\n");
diff --git a/tools/h5diff/h5diffgentest.c b/tools/h5diff/h5diffgentest.c
index dcfe76a..66f1ce8 100644
--- a/tools/h5diff/h5diffgentest.c
+++ b/tools/h5diff/h5diffgentest.c
@@ -312,11 +312,16 @@ int test_basic(const char *fname1, const char *fname2, const char *fname3)
     *-------------------------------------------------------------------------
     */
     {
-        /* epsilon = 0.00001 */
-        float  data11[3][2] ={{0.00000f,0.00001f},{0.00001f, 0.00000f},{0.00001f,0.00001f}};
-        float  data12[3][2] ={{0.00000f,0.00002f},{0.000009f,0.00001f},{0.00000f,0.00001f}};
-        double data13[3][2] ={{0.000000000,0.000000001},{0.000000001, 0.000000000},{0.000000001,0.000000001}};
-        double data14[3][2] ={{0.000000000,0.000000002},{0.0000000009,0.000000001},{0.000000000,0.000000001}};
+        /* epsilon = 0.0000001 = 1e-7 
+         * system epsilon for float : FLT_EPSILON = 1.19209E-07
+         */
+        float  data11[3][2] ={{0.000000f,0.0000001f},{0.0000001f, 0.00000022f},{0.0000001f,0.0000001f}};
+        float  data12[3][2] ={{0.000000f,0.0000002f},{0.0000003f,0.0000001f},{0.000000f,0.0000001f}};
+        /* epsilon = 0.0000000000000001 = 1e-16
+         * system epsilon for double : DBL_EPSILON = 2.22045E-16
+         */
+        double data13[3][2] ={{0.0000000000000000, 0.0000000000000001},{0.0000000000000001, 0.0000000000000000},{0.00000000000000033, 0.0000000000000001}};
+        double data14[3][2] ={{0.0000000000000000, 0.0000000000000004},{0.0000000000000002, 0.0000000000000001},{0.0000000000000001, 0.00000000000000000}};
 
         write_dset(gid1,2,dims2,"fp1",H5T_NATIVE_FLOAT,data11);
         write_dset(gid1,2,dims2,"fp2",H5T_NATIVE_FLOAT,data12);
diff --git a/tools/h5diff/testfiles/h5diff_10.txt b/tools/h5diff/testfiles/h5diff_10.txt
index 0b354df..8d6fc82 100644
--- a/tools/h5diff/testfiles/h5diff_10.txt
+++ b/tools/h5diff/testfiles/h5diff_10.txt
@@ -60,17 +60,11 @@ usage: h5diff [OPTIONS] file1 file2 [obj1[ obj2]]
                            number.
    -p R, --relative=R      Print difference if (|(a-b)/b| > R), R is a positive
                            number.
-   --use-system-epsilon    Print difference if (|a-b| > EPSILON),
-                           where EPSILON (FLT_EPSILON or FLT_EPSILON) is the
-                           system epsilon value. 
-                           If the system epsilon is not defined, use the value
-                           below:
+   --use-system-epsilon    Print difference if (|a-b| > EPSILON), EPSILON is
+                           a system epsilon value.
+                           The system epsilon values are defined as below:
                                FLT_EPSILON = 1.19209E-07 for float
                                DBL_EPSILON = 2.22045E-16 for double
-                           -d, -p, and --use-system-epsilon options are used for
-                           comparing floating point values.
-                           By default, strict equality is used. Use -p or -d to
-                           set specific tolerance.
    --exclude-path "path"   Exclude the specified path to an object when
                            comparing files or groups. If a group is excluded,
                            all member objects will also be excluded.
diff --git a/tools/h5diff/testfiles/h5diff_101.txt b/tools/h5diff/testfiles/h5diff_101.txt
index 1d0f38d..f915439 100644
--- a/tools/h5diff/testfiles/h5diff_101.txt
+++ b/tools/h5diff/testfiles/h5diff_101.txt
@@ -2,9 +2,10 @@ dataset: </g1/d1> and </g1/d2>
 size:           [3x2]           [3x2]
 position        d1              d2              difference          
 ------------------------------------------------------------
-[ 0 1 ]          1e-09           2e-09           1e-09          
-[ 1 0 ]          1e-09           9e-10           1e-10          
-[ 1 1 ]          0               1e-09           1e-09          
-[ 2 0 ]          1e-09           0               1e-09          
-4 differences found
+[ 0 1 ]          1e-16           4e-16           3e-16          
+[ 1 0 ]          1e-16           2e-16           1e-16          
+[ 1 1 ]          0               1e-16           1e-16          
+[ 2 0 ]          3.3e-16         1e-16           2.3e-16        
+[ 2 1 ]          1e-16           0               1e-16          
+5 differences found
 EXIT CODE: 1
diff --git a/tools/h5diff/testfiles/h5diff_101w.txt b/tools/h5diff/testfiles/h5diff_101w.txt
index 59176a2..d1f49da 100755
--- a/tools/h5diff/testfiles/h5diff_101w.txt
+++ b/tools/h5diff/testfiles/h5diff_101w.txt
@@ -2,9 +2,10 @@ dataset: </g1/d1> and </g1/d2>
 size:           [3x2]           [3x2]

 position        d1              d2              difference          

 ------------------------------------------------------------

-[ 0 1 ]          1e-009          2e-009          1e-009         

-[ 1 0 ]          1e-009          9e-010          1e-010         

-[ 1 1 ]          0               1e-009          1e-009         

-[ 2 0 ]          1e-009          0               1e-009         

-4 differences found

+[ 0 1 ]          1e-016          4e-016          3e-016         

+[ 1 0 ]          1e-016          2e-016          1e-016         

+[ 1 1 ]          0               1e-016          1e-016         

+[ 2 0 ]          3.3e-016        1e-016          2.3e-016       

+[ 2 1 ]          1e-016          0               1e-016         

+5 differences found

 EXIT CODE: 1

diff --git a/tools/h5diff/testfiles/h5diff_102.txt b/tools/h5diff/testfiles/h5diff_102.txt
index 30a2491..476067b 100644
--- a/tools/h5diff/testfiles/h5diff_102.txt
+++ b/tools/h5diff/testfiles/h5diff_102.txt
@@ -2,9 +2,9 @@ dataset: </g1/fp1> and </g1/fp2>
 size:           [3x2]           [3x2]
 position        fp1             fp2             difference          
 ------------------------------------------------------------
-[ 0 1 ]          1e-05           2e-05           1e-05          
-[ 1 0 ]          1e-05           9e-06           9.99999e-07    
-[ 1 1 ]          0               1e-05           1e-05          
-[ 2 0 ]          1e-05           0               1e-05          
+[ 0 1 ]          1e-07           2e-07           1e-07          
+[ 1 0 ]          1e-07           3e-07           2e-07          
+[ 1 1 ]          2.2e-07         1e-07           1.2e-07        
+[ 2 0 ]          1e-07           0               1e-07          
 4 differences found
 EXIT CODE: 1
diff --git a/tools/h5diff/testfiles/h5diff_102w.txt b/tools/h5diff/testfiles/h5diff_102w.txt
index 36a254e..dda3581 100755
--- a/tools/h5diff/testfiles/h5diff_102w.txt
+++ b/tools/h5diff/testfiles/h5diff_102w.txt
@@ -2,9 +2,9 @@ dataset: </g1/fp1> and </g1/fp2>
 size:           [3x2]           [3x2]

 position        fp1             fp2             difference          

 ------------------------------------------------------------

-[ 0 1 ]          1e-005          2e-005          1e-005         

-[ 1 0 ]          1e-005          9e-006          9.99999e-007   

-[ 1 1 ]          0               1e-005          1e-005         

-[ 2 0 ]          1e-005          0               1e-005         

+[ 0 1 ]          1e-007          2e-007          1e-007         

+[ 1 0 ]          1e-007          3e-007          2e-007         

+[ 1 1 ]          2.2e-007        1e-007          1.2e-007       

+[ 2 0 ]          1e-007          0               1e-007         

 4 differences found

 EXIT CODE: 1

diff --git a/tools/h5diff/testfiles/h5diff_103.txt b/tools/h5diff/testfiles/h5diff_103.txt
new file mode 100644
index 0000000..5700459
--- /dev/null
+++ b/tools/h5diff/testfiles/h5diff_103.txt
@@ -0,0 +1,8 @@
+dataset: </g1/d1> and </g1/d2>
+size:           [3x2]           [3x2]
+position        d1              d2              difference          
+------------------------------------------------------------
+[ 0 1 ]          1e-16           4e-16           3e-16          
+[ 2 0 ]          3.3e-16         1e-16           2.3e-16        
+2 differences found
+EXIT CODE: 1
diff --git a/tools/h5diff/testfiles/h5diff_103w.txt b/tools/h5diff/testfiles/h5diff_103w.txt
new file mode 100644
index 0000000..b1abea2
--- /dev/null
+++ b/tools/h5diff/testfiles/h5diff_103w.txt
@@ -0,0 +1,8 @@
+dataset: </g1/d1> and </g1/d2>
+size:           [3x2]           [3x2]
+position        d1              d2              difference          
+------------------------------------------------------------
+[ 0 1 ]          1e-016          4e-016          3e-016         
+[ 2 0 ]          3.3e-016        1e-016          2.3e-016       
+2 differences found
+EXIT CODE: 1
diff --git a/tools/h5diff/testfiles/h5diff_104.txt b/tools/h5diff/testfiles/h5diff_104.txt
new file mode 100644
index 0000000..2997f10
--- /dev/null
+++ b/tools/h5diff/testfiles/h5diff_104.txt
@@ -0,0 +1,8 @@
+dataset: </g1/fp1> and </g1/fp2>
+size:           [3x2]           [3x2]
+position        fp1             fp2             difference          
+------------------------------------------------------------
+[ 1 0 ]          1e-07           3e-07           2e-07          
+[ 1 1 ]          2.2e-07         1e-07           1.2e-07        
+2 differences found
+EXIT CODE: 1
diff --git a/tools/h5diff/testfiles/h5diff_104w.txt b/tools/h5diff/testfiles/h5diff_104w.txt
new file mode 100644
index 0000000..28ef705
--- /dev/null
+++ b/tools/h5diff/testfiles/h5diff_104w.txt
@@ -0,0 +1,8 @@
+dataset: </g1/fp1> and </g1/fp2>
+size:           [3x2]           [3x2]
+position        fp1             fp2             difference          
+------------------------------------------------------------
+[ 1 0 ]          1e-007          3e-007          2e-007         
+[ 1 1 ]          2.2e-007        1e-007          1.2e-007       
+2 differences found
+EXIT CODE: 1
diff --git a/tools/h5diff/testfiles/h5diff_600.txt b/tools/h5diff/testfiles/h5diff_600.txt
index efc05a8..e6e4607 100644
--- a/tools/h5diff/testfiles/h5diff_600.txt
+++ b/tools/h5diff/testfiles/h5diff_600.txt
@@ -60,17 +60,11 @@ usage: h5diff [OPTIONS] file1 file2 [obj1[ obj2]]
                            number.
    -p R, --relative=R      Print difference if (|(a-b)/b| > R), R is a positive
                            number.
-   --use-system-epsilon    Print difference if (|a-b| > EPSILON),
-                           where EPSILON (FLT_EPSILON or FLT_EPSILON) is the
-                           system epsilon value. 
-                           If the system epsilon is not defined, use the value
-                           below:
+   --use-system-epsilon    Print difference if (|a-b| > EPSILON), EPSILON is
+                           a system epsilon value.
+                           The system epsilon values are defined as below:
                                FLT_EPSILON = 1.19209E-07 for float
                                DBL_EPSILON = 2.22045E-16 for double
-                           -d, -p, and --use-system-epsilon options are used for
-                           comparing floating point values.
-                           By default, strict equality is used. Use -p or -d to
-                           set specific tolerance.
    --exclude-path "path"   Exclude the specified path to an object when
                            comparing files or groups. If a group is excluded,
                            all member objects will also be excluded.
diff --git a/tools/h5diff/testfiles/h5diff_603.txt b/tools/h5diff/testfiles/h5diff_603.txt
index c66c650..7b917d4 100644
--- a/tools/h5diff/testfiles/h5diff_603.txt
+++ b/tools/h5diff/testfiles/h5diff_603.txt
@@ -61,17 +61,11 @@ usage: h5diff [OPTIONS] file1 file2 [obj1[ obj2]]
                            number.
    -p R, --relative=R      Print difference if (|(a-b)/b| > R), R is a positive
                            number.
-   --use-system-epsilon    Print difference if (|a-b| > EPSILON),
-                           where EPSILON (FLT_EPSILON or FLT_EPSILON) is the
-                           system epsilon value. 
-                           If the system epsilon is not defined, use the value
-                           below:
+   --use-system-epsilon    Print difference if (|a-b| > EPSILON), EPSILON is
+                           a system epsilon value.
+                           The system epsilon values are defined as below:
                                FLT_EPSILON = 1.19209E-07 for float
                                DBL_EPSILON = 2.22045E-16 for double
-                           -d, -p, and --use-system-epsilon options are used for
-                           comparing floating point values.
-                           By default, strict equality is used. Use -p or -d to
-                           set specific tolerance.
    --exclude-path "path"   Exclude the specified path to an object when
                            comparing files or groups. If a group is excluded,
                            all member objects will also be excluded.
diff --git a/tools/h5diff/testfiles/h5diff_606.txt b/tools/h5diff/testfiles/h5diff_606.txt
index 705ae3e..110986a 100644
--- a/tools/h5diff/testfiles/h5diff_606.txt
+++ b/tools/h5diff/testfiles/h5diff_606.txt
@@ -61,17 +61,11 @@ usage: h5diff [OPTIONS] file1 file2 [obj1[ obj2]]
                            number.
    -p R, --relative=R      Print difference if (|(a-b)/b| > R), R is a positive
                            number.
-   --use-system-epsilon    Print difference if (|a-b| > EPSILON),
-                           where EPSILON (FLT_EPSILON or FLT_EPSILON) is the
-                           system epsilon value. 
-                           If the system epsilon is not defined, use the value
-                           below:
+   --use-system-epsilon    Print difference if (|a-b| > EPSILON), EPSILON is
+                           a system epsilon value.
+                           The system epsilon values are defined as below:
                                FLT_EPSILON = 1.19209E-07 for float
                                DBL_EPSILON = 2.22045E-16 for double
-                           -d, -p, and --use-system-epsilon options are used for
-                           comparing floating point values.
-                           By default, strict equality is used. Use -p or -d to
-                           set specific tolerance.
    --exclude-path "path"   Exclude the specified path to an object when
                            comparing files or groups. If a group is excluded,
                            all member objects will also be excluded.
diff --git a/tools/h5diff/testfiles/h5diff_612.txt b/tools/h5diff/testfiles/h5diff_612.txt
index d38e9d4..782f5b4 100644
--- a/tools/h5diff/testfiles/h5diff_612.txt
+++ b/tools/h5diff/testfiles/h5diff_612.txt
@@ -61,17 +61,11 @@ usage: h5diff [OPTIONS] file1 file2 [obj1[ obj2]]
                            number.
    -p R, --relative=R      Print difference if (|(a-b)/b| > R), R is a positive
                            number.
-   --use-system-epsilon    Print difference if (|a-b| > EPSILON),
-                           where EPSILON (FLT_EPSILON or FLT_EPSILON) is the
-                           system epsilon value. 
-                           If the system epsilon is not defined, use the value
-                           below:
+   --use-system-epsilon    Print difference if (|a-b| > EPSILON), EPSILON is
+                           a system epsilon value.
+                           The system epsilon values are defined as below:
                                FLT_EPSILON = 1.19209E-07 for float
                                DBL_EPSILON = 2.22045E-16 for double
-                           -d, -p, and --use-system-epsilon options are used for
-                           comparing floating point values.
-                           By default, strict equality is used. Use -p or -d to
-                           set specific tolerance.
    --exclude-path "path"   Exclude the specified path to an object when
                            comparing files or groups. If a group is excluded,
                            all member objects will also be excluded.
diff --git a/tools/h5diff/testfiles/h5diff_615.txt b/tools/h5diff/testfiles/h5diff_615.txt
index 4b95ea1..f816510 100644
--- a/tools/h5diff/testfiles/h5diff_615.txt
+++ b/tools/h5diff/testfiles/h5diff_615.txt
@@ -61,17 +61,11 @@ usage: h5diff [OPTIONS] file1 file2 [obj1[ obj2]]
                            number.
    -p R, --relative=R      Print difference if (|(a-b)/b| > R), R is a positive
                            number.
-   --use-system-epsilon    Print difference if (|a-b| > EPSILON),
-                           where EPSILON (FLT_EPSILON or FLT_EPSILON) is the
-                           system epsilon value. 
-                           If the system epsilon is not defined, use the value
-                           below:
+   --use-system-epsilon    Print difference if (|a-b| > EPSILON), EPSILON is
+                           a system epsilon value.
+                           The system epsilon values are defined as below:
                                FLT_EPSILON = 1.19209E-07 for float
                                DBL_EPSILON = 2.22045E-16 for double
-                           -d, -p, and --use-system-epsilon options are used for
-                           comparing floating point values.
-                           By default, strict equality is used. Use -p or -d to
-                           set specific tolerance.
    --exclude-path "path"   Exclude the specified path to an object when
                            comparing files or groups. If a group is excluded,
                            all member objects will also be excluded.
diff --git a/tools/h5diff/testfiles/h5diff_621.txt b/tools/h5diff/testfiles/h5diff_621.txt
index 56ed724..8dc8824 100644
--- a/tools/h5diff/testfiles/h5diff_621.txt
+++ b/tools/h5diff/testfiles/h5diff_621.txt
@@ -61,17 +61,11 @@ usage: h5diff [OPTIONS] file1 file2 [obj1[ obj2]]
                            number.
    -p R, --relative=R      Print difference if (|(a-b)/b| > R), R is a positive
                            number.
-   --use-system-epsilon    Print difference if (|a-b| > EPSILON),
-                           where EPSILON (FLT_EPSILON or FLT_EPSILON) is the
-                           system epsilon value. 
-                           If the system epsilon is not defined, use the value
-                           below:
+   --use-system-epsilon    Print difference if (|a-b| > EPSILON), EPSILON is
+                           a system epsilon value.
+                           The system epsilon values are defined as below:
                                FLT_EPSILON = 1.19209E-07 for float
                                DBL_EPSILON = 2.22045E-16 for double
-                           -d, -p, and --use-system-epsilon options are used for
-                           comparing floating point values.
-                           By default, strict equality is used. Use -p or -d to
-                           set specific tolerance.
    --exclude-path "path"   Exclude the specified path to an object when
                            comparing files or groups. If a group is excluded,
                            all member objects will also be excluded.
diff --git a/tools/h5diff/testfiles/h5diff_622.txt b/tools/h5diff/testfiles/h5diff_622.txt
index 6e2db1b..f2f2089 100644
--- a/tools/h5diff/testfiles/h5diff_622.txt
+++ b/tools/h5diff/testfiles/h5diff_622.txt
@@ -61,17 +61,11 @@ usage: h5diff [OPTIONS] file1 file2 [obj1[ obj2]]
                            number.
    -p R, --relative=R      Print difference if (|(a-b)/b| > R), R is a positive
                            number.
-   --use-system-epsilon    Print difference if (|a-b| > EPSILON),
-                           where EPSILON (FLT_EPSILON or FLT_EPSILON) is the
-                           system epsilon value. 
-                           If the system epsilon is not defined, use the value
-                           below:
+   --use-system-epsilon    Print difference if (|a-b| > EPSILON), EPSILON is
+                           a system epsilon value.
+                           The system epsilon values are defined as below:
                                FLT_EPSILON = 1.19209E-07 for float
                                DBL_EPSILON = 2.22045E-16 for double
-                           -d, -p, and --use-system-epsilon options are used for
-                           comparing floating point values.
-                           By default, strict equality is used. Use -p or -d to
-                           set specific tolerance.
    --exclude-path "path"   Exclude the specified path to an object when
                            comparing files or groups. If a group is excluded,
                            all member objects will also be excluded.
diff --git a/tools/h5diff/testfiles/h5diff_623.txt b/tools/h5diff/testfiles/h5diff_623.txt
index 910f4f0..840b127 100644
--- a/tools/h5diff/testfiles/h5diff_623.txt
+++ b/tools/h5diff/testfiles/h5diff_623.txt
@@ -61,17 +61,11 @@ usage: h5diff [OPTIONS] file1 file2 [obj1[ obj2]]
                            number.
    -p R, --relative=R      Print difference if (|(a-b)/b| > R), R is a positive
                            number.
-   --use-system-epsilon    Print difference if (|a-b| > EPSILON),
-                           where EPSILON (FLT_EPSILON or FLT_EPSILON) is the
-                           system epsilon value. 
-                           If the system epsilon is not defined, use the value
-                           below:
+   --use-system-epsilon    Print difference if (|a-b| > EPSILON), EPSILON is
+                           a system epsilon value.
+                           The system epsilon values are defined as below:
                                FLT_EPSILON = 1.19209E-07 for float
                                DBL_EPSILON = 2.22045E-16 for double
-                           -d, -p, and --use-system-epsilon options are used for
-                           comparing floating point values.
-                           By default, strict equality is used. Use -p or -d to
-                           set specific tolerance.
    --exclude-path "path"   Exclude the specified path to an object when
                            comparing files or groups. If a group is excluded,
                            all member objects will also be excluded.
diff --git a/tools/h5diff/testfiles/h5diff_624.txt b/tools/h5diff/testfiles/h5diff_624.txt
index e301645..1d433a7 100644
--- a/tools/h5diff/testfiles/h5diff_624.txt
+++ b/tools/h5diff/testfiles/h5diff_624.txt
@@ -61,17 +61,11 @@ usage: h5diff [OPTIONS] file1 file2 [obj1[ obj2]]
                            number.
    -p R, --relative=R      Print difference if (|(a-b)/b| > R), R is a positive
                            number.
-   --use-system-epsilon    Print difference if (|a-b| > EPSILON),
-                           where EPSILON (FLT_EPSILON or FLT_EPSILON) is the
-                           system epsilon value. 
-                           If the system epsilon is not defined, use the value
-                           below:
+   --use-system-epsilon    Print difference if (|a-b| > EPSILON), EPSILON is
+                           a system epsilon value.
+                           The system epsilon values are defined as below:
                                FLT_EPSILON = 1.19209E-07 for float
                                DBL_EPSILON = 2.22045E-16 for double
-                           -d, -p, and --use-system-epsilon options are used for
-                           comparing floating point values.
-                           By default, strict equality is used. Use -p or -d to
-                           set specific tolerance.
    --exclude-path "path"   Exclude the specified path to an object when
                            comparing files or groups. If a group is excluded,
                            all member objects will also be excluded.
diff --git a/tools/h5diff/testfiles/h5diff_basic1.h5 b/tools/h5diff/testfiles/h5diff_basic1.h5
index 4ed83c8..4f3cf9a 100644
--- a/tools/h5diff/testfiles/h5diff_basic1.h5
+++ b/tools/h5diff/testfiles/h5diff_basic1.h5
diff --git a/tools/h5diff/testh5diff.sh b/tools/h5diff/testh5diff.sh
index 926ea27..1a4d5e8 100755
--- a/tools/h5diff/testh5diff.sh
+++ b/tools/h5diff/testh5diff.sh
@@ -601,10 +601,18 @@ else
 fi
 
 # 11. floating point comparison
+# double value
 TOOLTEST h5diff_101.txt -v $FILE1 $FILE1 g1/d1  g1/d2 
 
+# float value
 TOOLTEST h5diff_102.txt -v $FILE1 $FILE1 g1/fp1 g1/fp2 
 
+# with --use-system-epsilon for double value 
+TOOLTEST h5diff_103.txt -v --use-system-epsilon $FILE1 $FILE1 g1/d1  g1/d2 
+
+# with --use-system-epsilon for float value
+TOOLTEST h5diff_104.txt -v --use-system-epsilon $FILE1 $FILE1 g1/fp1 g1/fp2 
+
 
 # not comparable -c flag
 TOOLTEST h5diff_200.txt $FILE2 $FILE2 g2/dset1  g2/dset2 
diff --git a/tools/lib/h5diff_array.c b/tools/lib/h5diff_array.c
index 9a609b5..c4c8dbf 100644
--- a/tools/lib/h5diff_array.c
+++ b/tools/lib/h5diff_array.c
@@ -5550,7 +5550,7 @@ error:
 /*-------------------------------------------------------------------------
  * Function:    equal_double
  *
- * Purpose:     use a relative error formula to deal with floating point
+ * Purpose:     use a absolute error formula to deal with floating point
  *              uncertainty
  *
  * Modifications:
@@ -5604,7 +5604,7 @@ hbool_t equal_double(double value, double expected, diff_opt_t *options)
 /*-------------------------------------------------------------------------
  * Function:    equal_ldouble
  *
- * Purpose:     use a relative error formula to deal with floating point
+ * Purpose:     use a absolute error formula to deal with floating point
  *              uncertainty
  *
  *-------------------------------------------------------------------------
@@ -5660,7 +5660,7 @@ hbool_t equal_ldouble(long double value, long double expected, diff_opt_t *optio
 /*-------------------------------------------------------------------------
  * Function:    equal_float
  *
- * Purpose:     use a relative error formula to deal with floating point
+ * Purpose:     use a absolute error formula to deal with floating point
  *              uncertainty
  *
  * Modifications: