src/share/classes/java/util/stream/DoublePipeline.java

@@ -375,12 +375,19 @@
         evaluate(ForEachOps.makeDouble(consumer, true));
     }
 
     @Override
     public final double sum() {
-        // TODO: better algorithm to compensate for errors
-        return reduce(0.0, Double::sum);
+        double[] summation = collect(() -> new double[2],
+                               (ll, d) -> {
+                                   Collectors.sumWithCompensation(ll, d);
+                               },
+                               (ll, rr) -> {
+                                   Collectors.sumWithCompensation(ll, rr[0]);
+                                   Collectors.sumWithCompensation(ll, rr[1]);
+                               });
+        return summation[0];
     }
 
     @Override
     public final OptionalDouble min() {
         return reduce(Math::min);

@@ -391,21 +398,22 @@
         return reduce(Math::max);
     }
 
     @Override
     public final OptionalDouble average() {
-        double[] avg = collect(() -> new double[2],
-                               (ll, i) -> {
-                                   ll[0]++;
-                                   ll[1] += i;
+        double[] avg = collect(() -> new double[3],
+                               (ll, d) -> {
+                                   ll[2]++;
+                                   Collectors.sumWithCompensation(ll, d);
                                },
                                (ll, rr) -> {
-                                   ll[0] += rr[0];
-                                   ll[1] += rr[1];
+                                   Collectors.sumWithCompensation(ll, rr[0]);
+                                   Collectors.sumWithCompensation(ll, rr[1]);
+                                   ll[2] += rr[2];
                                });
         return avg[0] > 0
-               ? OptionalDouble.of(avg[1] / avg[0])
+               ? OptionalDouble.of(avg[0] / avg[2])
                : OptionalDouble.empty();
     }
 
     @Override
     public final long count() {