provide a moving aggregate of statistics on generated values

virtdata-lib-basics/src/main/java/io/nosqlbench/virtdata/library/basics/shared/statistics/LongStats.java

@@ -0,0 +1,73 @@
+package io.nosqlbench.virtdata.library.basics.shared.statistics;
+
+import io.nosqlbench.virtdata.api.annotations.Categories;
+import io.nosqlbench.virtdata.api.annotations.Category;
+import io.nosqlbench.virtdata.api.annotations.ThreadSafeMapper;
+import io.nosqlbench.virtdata.api.bindings.VirtDataFunctions;
+
+import java.util.DoubleSummaryStatistics;
+import java.util.Locale;
+import java.util.function.DoubleSupplier;
+import java.util.function.DoubleUnaryOperator;
+
+/**
+ * Provide a moving aggregate (min,max,avg,sum,count) of long values presented.
+ * This allows for sanity checks on values during prototyping, primarily.
+ * Using it for other purposes in actual workloads is not generally desirable,
+ * as this does not produce purely functional (deterministic) values.
+ */
+@ThreadSafeMapper
+@Categories({Category.statistics})
+public class LongStats implements DoubleUnaryOperator {
+
+    DoubleSummaryStatistics stats = new DoubleSummaryStatistics();
+    DoubleSupplier accessor;
+    DoubleUnaryOperator valueFunc;
+
+    /**
+     * Given the specified statistic, provide an
+     * updated result for all the values presented to this function's input.
+     * @param spec One of 'min', 'max', 'count', 'avg', or 'sum'
+     */
+    public LongStats(String spec) {
+        this(spec,(DoubleUnaryOperator) v->v, true);
+    }
+
+    /**
+     * Given the specified statistic, a function, and whether to allow truncating conversions,
+     * provide an updated result for all the values produced by the provided function when
+     * given the input.
+     * @param spec One of 'min', 'max', 'count', 'avg', or 'sum'
+     * @param func Any function which can take a long or compatible input and produce a numeric value
+     * @param truncate Whether or not to allow truncating conversions (long to int for example)
+     */
+    public LongStats(String spec,Object func, boolean truncate) {
+        switch (spec.toLowerCase(Locale.ROOT)) {
+            case "min":
+                accessor = stats::getMin;
+                break;
+            case "max":
+                accessor = stats::getMax;
+                break;
+            case "average":
+            case "avg":
+                accessor = stats::getAverage;
+                break;
+            case "count":
+                accessor = stats::getCount;
+                break;
+            case "sum":
+                accessor = stats::getSum;
+                break;
+            default:
+                throw new RuntimeException("You must specify one of min,max,avg,count,sum");
+        }
+        valueFunc= VirtDataFunctions.adapt(func,DoubleUnaryOperator.class,double.class,truncate);
+    }
+
+    @Override
+    public double applyAsDouble(double operand) {
+        stats.accept(valueFunc.applyAsDouble(operand));
+        return accessor.getAsDouble();
+    }
+}