move stat bucket up to core api

nb-apis/nb-api/src/main/java/io/nosqlbench/nb/api/stats/DoubleRing.java

@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 
-package io.nosqlbench.scenarios.simframe.stabilization;
+package io.nosqlbench.nb.api.stats;
 
 public class DoubleRing {
     private final double[] dbuf;
@@ -47,4 +47,21 @@ public class DoubleRing {
     public int count() {
         return count;
     }
+
+    public double min() {
+        double min = Double.MAX_VALUE;
+        for (int i = 0; i < count; i++) {
+            min = Math.min(min,dbuf[i]);
+        }
+        return min;
+    }
+
+    public double max() {
+        double max = Double.MIN_VALUE;
+        for (int i = 0; i < count; i++) {
+            max = Math.max(max,dbuf[i]);
+        }
+        return max;
+    }
+
 }

nb-apis/nb-api/src/main/java/io/nosqlbench/nb/api/stats/StatBucket.java

@@ -14,10 +14,16 @@
  * limitations under the License.
  */
 
-package io.nosqlbench.scenarios.simframe.stabilization;
+package io.nosqlbench.nb.api.stats;
 
 import java.util.Objects;
 
+/**
+ * This is a relatively efficient statistics bucket which can maintain moving
+ * aggregates over a window of samples for count, mean, variance, stddev, sum.
+ * This is particularly useful when you know that each update to the data
+ * will likely be used in a query.
+ */
 public final class StatBucket {
     DoubleRing ringbuf;
     private double mean;
@@ -98,10 +104,31 @@ public final class StatBucket {
         return "StatBucket[" +
             "count=" + ringbuf.count() + ", " +
             "mean=" + mean + ", " +
-            "stddev=" + stddev() + ']';
+            "stddev=" + stddev()  + ", " +
+            "variance=" + variance() + ']';
     }
 
     public boolean primed() {
         return this.count()== ringbuf.size();
     }
+
+    public double getMin() {
+        return ringbuf.min();
+    }
+
+    public double getMax() {
+        return ringbuf.max();
+    }
+
+    public double getAverage() {
+        return this.mean();
+    }
+
+    public double getCount() {
+        return count();
+    }
+
+    public double getSum() {
+        return this.mean() * this.count();
+    }
 }

nb-apis/nb-api/src/test/java/io/nosqlbench/nb/api/stats/StatBucketTest.java

@@ -0,0 +1,70 @@
+/*
+ * Copyright (c) 2023 nosqlbench
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package io.nosqlbench.nb.api.stats;
+
+import org.assertj.core.data.Offset;
+import org.junit.jupiter.api.Test;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+class StatBucketTest {
+    @Test
+    public void testStreamingMean() {
+        var bucket = new StatBucket();
+        bucket.apply(5.0d);
+        assertThat(bucket.mean()).isCloseTo(5.0d, Offset.offset(0.001d));
+        bucket.apply(10.0d);
+        assertThat(bucket.mean()).isCloseTo(7.5d, Offset.offset(0.001d));
+        bucket.apply(15.0d);
+        assertThat(bucket.mean()).isCloseTo(10.0d, Offset.offset(0.001d));
+        bucket.apply(20.0d);
+        assertThat(bucket.mean()).isCloseTo(12.5d, Offset.offset(0.001d));
+    }
+
+    @Test
+    public void testStreamingComputations() {
+        double[] samples = new double[]{2, 4, 4, 4, 5, 5, 7, 9};
+
+        var bucket = new StatBucket(8);
+        for (int i = 0; i < samples.length * 10; i++) {
+            bucket.apply(samples[i % samples.length]);
+            if (i > 0 && (i % samples.length) == 0) {
+                assertThat(bucket.mean()).isCloseTo(5, Offset.offset(0.001d));
+                assertThat(bucket.stddev()).isCloseTo(2.0, Offset.offset(0.001d));
+            }
+        }
+    }
+
+    @Test
+    public void testErrorAccumulation1() {
+        var bucket = new StatBucket(11);
+        for (long base = 1; base <10000000000000000L ; base*=10) {
+            for (int i = 0; i< 10; i++) {
+                long value = base+i;
+                bucket.apply(value);
+            }
+            for (int i = 10; i < 20; i++) {
+                long value = base+i;
+                bucket.apply(value);
+                double streamingMean = bucket.mean();
+                assertThat(streamingMean).isCloseTo((double)(value-5), Offset.offset(0.03d));
+            }
+        }
+
+    }
+
+}

nbr/src/main/java/io/nosqlbench/scenarios/simframe/stabilization/StabilityDetector.java

@@ -16,12 +16,12 @@
 
 package io.nosqlbench.scenarios.simframe.stabilization;
 
+import io.nosqlbench.nb.api.stats.StatBucket;
 import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.Logger;
 
 import java.util.Arrays;
 import java.util.List;
-import java.util.OptionalDouble;
 import java.util.function.DoubleSupplier;
 import java.util.function.Supplier;
 

nbr/src/test/java/io/nosqlbench/scenarios/simframe/stats/StatBucketTest.java

@@ -1,53 +0,0 @@
-/*
- * Copyright (c) 2023 nosqlbench
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-package io.nosqlbench.scenarios.simframe.stats;
-
-import io.nosqlbench.scenarios.simframe.stabilization.StatBucket;
-import org.assertj.core.data.Offset;
-import org.junit.jupiter.api.Test;
-
-import static org.assertj.core.api.Assertions.assertThat;
-
-class StatBucketTest {
-    @Test
-    public void testStreamingMean() {
-        var bucket  = new StatBucket();
-        bucket.apply(5.0d);
-        assertThat(bucket.mean()).isCloseTo(5.0d,Offset.offset(0.001d));
-        bucket.apply(10.0d);
-        assertThat(bucket.mean()).isCloseTo(7.5d,Offset.offset(0.001d));
-        bucket.apply(15.0d);
-        assertThat(bucket.mean()).isCloseTo(10.0d,Offset.offset(0.001d));
-        bucket.apply(20.0d);
-        assertThat(bucket.mean()).isCloseTo(12.5d,Offset.offset(0.001d));
-    }
-
-    @Test
-    public void testStreamingComputations() {
-        double[] samples = new double[]{2,4,4,4,5,5,7,9};
-
-        var bucket  = new StatBucket(8);
-        for (int i = 0; i < samples.length * 10; i++) {
-            bucket.apply(samples[i%samples.length]);
-            if (i>0&&(i%samples.length)==0) {
-                assertThat(bucket.mean()).isCloseTo(5,Offset.offset(0.001d));
-                assertThat(bucket.stddev()).isCloseTo(2.0,Offset.offset(0.001d));
-            }
-        }
-    }
-
-}