From 609785d50341911dd4d6ac48cc5e1bf09180eb45 Mon Sep 17 00:00:00 2001
From: Michael Zhang <mail@mzhang.io>
Date: Mon, 6 Sep 2021 16:03:42 -0500
Subject: [PATCH] means

---
 nonpers-assignment/.gitignore                 |  3 ++
 .../mean/DampedItemMeanModelProvider.java     | 33 +++++++++++++++++--
 .../nonpers/mean/ItemMeanModelProvider.java   | 19 ++++++++---
 3 files changed, 49 insertions(+), 6 deletions(-)

diff --git a/nonpers-assignment/.gitignore b/nonpers-assignment/.gitignore
index 08a55c0..2b4c1b4 100644
--- a/nonpers-assignment/.gitignore
+++ b/nonpers-assignment/.gitignore
@@ -1 +1,4 @@
 .gradle
+.project
+.settings
+build
diff --git a/nonpers-assignment/src/main/java/org/lenskit/mooc/nonpers/mean/DampedItemMeanModelProvider.java b/nonpers-assignment/src/main/java/org/lenskit/mooc/nonpers/mean/DampedItemMeanModelProvider.java
index afe0463..b489c5f 100644
--- a/nonpers-assignment/src/main/java/org/lenskit/mooc/nonpers/mean/DampedItemMeanModelProvider.java
+++ b/nonpers-assignment/src/main/java/org/lenskit/mooc/nonpers/mean/DampedItemMeanModelProvider.java
@@ -2,6 +2,7 @@ package org.lenskit.mooc.nonpers.mean;
 
 import it.unimi.dsi.fastutil.longs.Long2DoubleOpenHashMap;
 import it.unimi.dsi.fastutil.longs.Long2IntOpenHashMap;
+import it.unimi.dsi.fastutil.longs.LongSet;
 import org.lenskit.baseline.MeanDamping;
 import org.lenskit.data.dao.DataAccessObject;
 import org.lenskit.data.ratings.Rating;
@@ -62,7 +63,35 @@ public class DampedItemMeanModelProvider implements Provider<ItemMeanModel> {
     @Override
     public ItemMeanModel get() {
         // TODO Compute damped means
-        // TODO Remove the line below when you have finished
-        throw new UnsupportedOperationException("damped mean not implemented");
+        Long2DoubleOpenHashMap means = new Long2DoubleOpenHashMap();
+        Long2IntOpenHashMap lens = new Long2IntOpenHashMap();
+        double globalMean = 0;
+        int globalLen = 0;
+
+        try (ObjectStream<Rating> ratings = dao.query(Rating.class).stream()) {
+            for (Rating r: ratings) {
+                // this loop will run once for each rating in the data set
+                means.addTo(r.getItemId(), r.getValue());
+                lens.addTo(r.getItemId(), 1);
+
+                globalMean += r.getValue();
+                globalLen += 1;
+            }
+        }
+
+        globalMean /= globalLen;
+
+        LongSet keys = means.keySet();
+        for (long key : keys) {
+            double val = means.get(key);
+            val = (val + damping * globalMean) / (lens.get(key) + damping);
+            means.put(key, val);
+
+            if (key == 2959 || key == 1203) {
+                logger.info("Damped mean for item {} is {}", key, val);
+            }
+        }
+
+        return new ItemMeanModel(means);
     }
 }
diff --git a/nonpers-assignment/src/main/java/org/lenskit/mooc/nonpers/mean/ItemMeanModelProvider.java b/nonpers-assignment/src/main/java/org/lenskit/mooc/nonpers/mean/ItemMeanModelProvider.java
index 62935b3..a4656c5 100644
--- a/nonpers-assignment/src/main/java/org/lenskit/mooc/nonpers/mean/ItemMeanModelProvider.java
+++ b/nonpers-assignment/src/main/java/org/lenskit/mooc/nonpers/mean/ItemMeanModelProvider.java
@@ -2,6 +2,7 @@ package org.lenskit.mooc.nonpers.mean;
 
 import it.unimi.dsi.fastutil.longs.Long2DoubleOpenHashMap;
 import it.unimi.dsi.fastutil.longs.Long2IntOpenHashMap;
+import it.unimi.dsi.fastutil.longs.LongSet;
 import org.lenskit.data.dao.DataAccessObject;
 import org.lenskit.data.ratings.Rating;
 import org.lenskit.inject.Transient;
@@ -51,17 +52,27 @@ public class ItemMeanModelProvider implements Provider<ItemMeanModel> {
      */
     @Override
     public ItemMeanModel get() {
-        // TODO Set up data structures for computing means
+        Long2DoubleOpenHashMap means = new Long2DoubleOpenHashMap();
+        Long2IntOpenHashMap lens = new Long2IntOpenHashMap();
 
         try (ObjectStream<Rating> ratings = dao.query(Rating.class).stream()) {
             for (Rating r: ratings) {
                 // this loop will run once for each rating in the data set
-                // TODO process this rating
+                means.addTo(r.getItemId(), r.getValue());
+                lens.addTo(r.getItemId(), 1);
             }
         }
 
-        Long2DoubleOpenHashMap means = new Long2DoubleOpenHashMap();
-        // TODO Finalize means to store them in the mean model
+        LongSet keys = means.keySet();
+        for (long key : keys) {
+            double val = means.get(key);
+            val /= lens.get(key);
+            means.put(key, val);
+
+            if (key == 2959 || key == 1203) {
+                logger.info("Damped mean for item {} is {}", key, val);
+            }
+        }
 
         logger.info("computed mean ratings for {} items", means.size());
         return new ItemMeanModel(means);