Don't return a value before the first valid data point.

src/utility/sampledDistribution.H

@@ -98,30 +98,39 @@ public:
 
   uint32   getValue(double d) {
 
-    if (d < 0.0)  d = 0.0;
-    if (d > 1.0)  d = 1.0;
+    //  Imagine our input histogram (value occurences) is expanded into an
+    //  array of (_dataSum) values, where each 'value' in the input histogram
+    //  is listed 'occurences' times (and that it's sorted).
+    //
+    //  For input 0 <= 'd' < 1, we want to return the 'value' that is at that
+    //  position in the array.
+
+    if (d < 0.0)  d = 0.0;   //  Limit our input (random) number
+    if (d > 1.0)  d = 1.0;   //  to valid scaling range.
 
-    uint64  pos = 0;
     uint64  lim = (uint64)floor(_dataSum * d);
 
-    if (pos >= _dataSum)   pos = _dataSum;
+    //  Scan the _data, looking for the _data element that contains the 'lim'th
+    //  entry in the (imagined) array.
 
-    while (_data[pos] < lim) {
-      lim -= _data[pos];
-      pos += 1;
-    }
+    uint64  value = 0;              //  value we're testing.
+
+    while (_data[value] <= lim) {   //  If _data[value] is more than the current
+      lim -= _data[value];          //  limit, we're found the value, otherwise,
+      value += 1;                   //  decrement the limit by the occurrences
+    }                               //  for this value and move to the next.
 
-    assert(pos < _dataLen);
+    assert(value < _dataLen);
 
-    return(pos);
+    return(value);
   };
 
 
 public:
-  uint32   _dataLen;   //  Highest valid point
-  uint32   _dataMax;   //  Number allocated
-  uint32  *_data;
+  uint32   _dataLen;   //  Length of the valid data in _data: _data[_dataLen-1] is the last valid data point.
+  uint32   _dataMax;   //  Allocated size of _data.
+  uint32  *_data;      //  Number of data points of value x:  _data[x] == v <-> 'x' was present 'v' times in the input.
 
-  uint64   _dataSum;
+  uint64   _dataSum;   //  Number of points in the input.  It's the sum of all _data[x].
 };