[MOAB-dev] r3442 - MOAB/trunk

[kraftche at cae.wisc.edu]

Author: kraftche
Date: 2010-01-19 18:45:55 -0600 (Tue, 19 Jan 2010)
New Revision: 3442

Modified:
   MOAB/trunk/BitTagServer.cpp
   MOAB/trunk/BitTagServer.hpp
Log:
Fix bug in BitTagServer.

When re-writing BitTagServer, I initially used variable-sized bit pages
(as a function of bits per tag value.)  It appears that I only partially
checked in the change to fixed-size pages.  It is interesting (in an 
unfortunate way) that this code worked as checked in.  


Modified: MOAB/trunk/BitTagServer.cpp
===================================================================
--- MOAB/trunk/BitTagServer.cpp	2010-01-20 00:43:23 UTC (rev 3441)
+++ MOAB/trunk/BitTagServer.cpp	2010-01-20 00:45:55 UTC (rev 3442)
@@ -76,10 +76,17 @@
     // store smallest power of two greater than or 
     // equal to the number of bits
   storedBitsPerEntity = 1;
-  pageShift = Ln2PageSize+1;
+  unsigned ln2storedbits = 0;
   while (storedBitsPerEntity < bits) {
     storedBitsPerEntity *= 2;
+    ++ln2storedbits;
   }
+  
+  // pageShift = log2( ents_per_page() )
+  //           = log2( 8 * pageSize / storedBitsPerEntity )
+  //           = log2(8) + log2(pageSize) - log2(storedBitsPerEntity)
+  //           = 3 * Ln2PageSize - ln2storedbits;
+  pageShift = 3 + Ln2PageSize - ln2storedbits;
 
   return MB_SUCCESS;
 }

Modified: MOAB/trunk/BitTagServer.hpp
===================================================================
--- MOAB/trunk/BitTagServer.hpp	2010-01-20 00:43:23 UTC (rev 3441)
+++ MOAB/trunk/BitTagServer.hpp	2010-01-20 00:45:55 UTC (rev 3442)
@@ -259,7 +259,7 @@
   std::vector<BitPage*> pageList[MBMAXTYPE]; //!< Array of BitPage instances storing actual data.
   unsigned int requestedBitsPerEntity; //!< user-requested bits per entity
   unsigned int storedBitsPerEntity;    //!< allocated bits per entity (power of 2)
-  unsigned int pageShift;              //!< Ln2PageSize + log2(storedBitsPerEntity)
+  unsigned int pageShift;              //!< log2( ents_per_page() )
   
   /**\brief Get indices from handle 
    *
@@ -271,8 +271,8 @@
     { 
       type = TYPE_FROM_HANDLE(h);
       h = ID_FROM_HANDLE(h);
-      page = ((size_t)h) >> pageShift;   // h / (offset*storedBitsPerEntity)
-      offset = h & ((1u<<pageShift)-1u); // h % (offset*storedBitsPerEntity)
+      page = ((size_t)h) >> pageShift;   // h / ents_per_page()
+      offset = h & ((1u<<pageShift)-1u); // h % ends_per_page()
     }
     
   /**\brief Get the number of tag values that are stored in each BitPage */