Just FYI, As mentioned below, hard-coded default value for alpha (0.15) should be replaced.
---------- Forwarded message ---------- From: Yunkai Zhang <[email protected]> Date: Fri, Jun 24, 2011 at 9:51 AM Subject: A bug in the PageRank example To: [email protected] Hi, I am playing with the pagerank example from trunk and found there is a bug in the code. If I assign any value other than 0.85 to the damping factor, the results won't sum to 1. For example: Set damping factor to *0.5* 11/06/23 17:28:05 INFO graph.PageRankBase: -------------------- RESULTS -------------------- 11/06/23 17:28:06 INFO graph.PageRankBase: stackoverflow.com | 0.052213531500120945 11/06/23 17:28:06 INFO graph.PageRankBase: nasa.gov | 0.04235399497763073 11/06/23 17:28:06 INFO graph.PageRankBase: facebook.com | 0.030321424044325564 11/06/23 17:28:06 INFO graph.PageRankBase: yahoo.com | 0.05650175656380897 11/06/23 17:28:07 INFO graph.PageRankBase: youtube.com | 0.025716796492259456 11/06/23 17:28:07 INFO graph.PageRankBase: google.com | 0.07350857237752877 11/06/23 17:28:07 INFO graph.PageRankBase: twitter.com | 0.030321424044325564 The sum is 0.3ish. Therefore, I read the code. I think a possible reason is that the value of * ALPHA* is hard-coded. (Formula: P(i) = ALPHA + 0.85 * sum, ALPHA = 0.15 / NumVertices() ) In PageRank.java, line 167: ALPHA = *0.15* / (double) numOfVertices; I think 0.15 should be replaced by (1 - DAMPING_FACTOR). Thanks! Best, Benny -- Best Regards, Edward J. Yoon @eddieyoon
