--- loncom/interface/statistics/lonstathelpers.pm	2004/03/12 21:05:08	1.7
+++ loncom/interface/statistics/lonstathelpers.pm	2004/03/16 16:30:31	1.8
@@ -1,6 +1,6 @@
 # The LearningOnline Network with CAPA
 #
-# $Id: lonstathelpers.pm,v 1.7 2004/03/12 21:05:08 matthew Exp $
+# $Id: lonstathelpers.pm,v 1.8 2004/03/16 16:30:31 matthew Exp $
 #
 # Copyright Michigan State University Board of Trustees
 #
@@ -59,6 +59,8 @@ use Apache::lonlocal;
 use HTML::Entities();
 use Time::Local();
 use Spreadsheet::WriteExcel();
+use GDBM_File;
+use Storable qw(freeze thaw);
 
 ####################################################
 ####################################################
@@ -369,6 +371,10 @@ sub analyze_problem_as_student {
     my $returnvalue;
     my $url = $resource->{'src'};
     my $symb = $resource->{'symb'};
+    my $answer = &get_from_answer_cache($sname,$sdom,$symb,$partid,$respid);
+    if (defined($answer)) {
+        return($answer);
+    }
     my $courseid = $ENV{'request.course.id'};
     my $Answ=&Apache::lonnet::ssi($url,('grade_target' => 'analyze',
                                         'grade_domain' => $sdom,
@@ -378,27 +384,22 @@ sub analyze_problem_as_student {
     (my $garbage,$Answ)=split(/_HASH_REF__/,$Answ,2);
     my %Answer=&Apache::lonnet::str2hash($Answ);
     #
-    if (! defined($partid)) {
-        # If you do not specify a partid, you get them all.
-        foreach my $partid (@{$resource->{'parts'}}) {
-            my $partdata = $resource->{'partdata'}->{$partid};
-            foreach my $respid (@{$partdata->{'ResponseIds'}}) {
-                my $prefix = $partid.'.'.$respid;
-                my $key = $prefix.'.answer';
-                $returnvalue->{$key} = &get_answer($prefix,$key,%Answer);
-            }
-        }
-    } elsif (! defined($respid)) {
+    undef($answer);
+    foreach my $partid (@{$resource->{'parts'}}) {
         my $partdata = $resource->{'partdata'}->{$partid};
         foreach my $respid (@{$partdata->{'ResponseIds'}}) {
             my $prefix = $partid.'.'.$respid;
             my $key = $prefix.'.answer';
-            $returnvalue->{$key} = &get_answer($prefix,$key,%Answer);
+            $answer->{$partid}->{$respid} = &get_answer($prefix,$key,%Answer);
         }
+    }
+    &store_answer($sname,$sdom,$symb,undef,undef,$answer);
+    if (! defined($partid)) {
+        $returnvalue = $answer;
+    } elsif (! defined($respid)) {
+        $returnvalue = $answer->{$partid};
     } else {
-        my $prefix = $partid.'.'.$respid;
-        my $key = $prefix.'.answer';
-        $returnvalue = &get_answer($prefix,$key,%Answer);
+        $returnvalue = $answer->{$partid}->{$respid};
     }
     return $returnvalue;
 }
@@ -437,6 +438,191 @@ sub get_answer {
     return $returnvalue;
 }
 
+
+#####################################################
+#####################################################
+
+=pod
+
+=item Caching routines
+
+=over 4
+
+=item &load_answer_cache($symb)
+
+Loads the cache for the given symb into memory from disk.  
+Requires the cache filename be set.  
+Only should be called by &ensure_proper_cache.
+
+=cut
+
+#####################################################
+#####################################################
+{
+    my $cache_filename = undef;
+    my $current_symb = undef;
+    my %cache;
+
+sub load_answer_cache {
+    my ($symb) = @_;
+    return if (! defined($cache_filename));
+    if (! defined($current_symb) || $current_symb ne $symb) {
+        undef(%cache);
+        my $storedstring;
+        my %cache_db;
+        if (tie(%cache_db,'GDBM_File',$cache_filename,&GDBM_READER(),0640)) {
+            $storedstring = $cache_db{&Apache::lonnet::escape($symb)};
+            untie(%cache_db);
+        }
+        if (defined($storedstring)) {
+            %cache = %{thaw($storedstring)};
+        }
+    }
+    return;
+}
+
+#####################################################
+#####################################################
+
+=pod
+
+=item &get_from_answer_cache($sname,$sdom,$symb,$partid,$respid)
+
+Returns the appropriate data from the cache, or undef if no data exists.
+If $respid is undefined, a hash ref containing the answers for the given 
+$partid is returned.  If $partid is undefined, a hash ref containing answers
+for all of the parts is returned.
+
+=cut
+
+#####################################################
+#####################################################
+sub get_from_answer_cache {
+    my ($sname,$sdom,$symb,$partid,$respid) = @_;
+    &ensure_proper_cache($symb);
+    my $returnvalue;
+    if (exists($cache{$sname.':'.$sdom}) &&
+        ref($cache{$sname.':'.$sdom}) eq 'HASH') {
+        if (defined($partid) &&
+            exists($cache{$sname.':'.$sdom}->{$partid})) {
+            if (defined($respid) &&
+                exists($cache{$sname.':'.$sdom}->{$partid}->{$respid})) {
+                $returnvalue = $cache{$sname.':'.$sdom}->{$partid}->{$respid};
+            } else {
+                $returnvalue = $cache{$sname.':'.$sdom}->{$partid};
+            }
+        } else {
+            $returnvalue = $cache{$sname.':'.$sdom};
+        }
+    } else {
+        $returnvalue = undef;
+    }
+    return $returnvalue;
+}
+
+#####################################################
+#####################################################
+
+=pod
+
+=item &write_answer_cache($symb)
+
+Writes the in memory cache to disk so that it can be read in with
+&load_answer_cache($symb).
+
+=cut
+
+#####################################################
+#####################################################
+sub write_answer_cache {
+    return if (! defined($current_symb) || ! defined($cache_filename));
+    my %cache_db;
+    my $key = &Apache::lonnet::escape($current_symb);
+    if (tie(%cache_db,'GDBM_File',$cache_filename,&GDBM_WRCREAT(),0640)) {
+        my $storestring = freeze(\%cache);
+        $cache_db{$key}=$storestring;
+        $cache_db{$key.'.time'}=time;
+        untie(%cache_db);
+    }
+    undef(%cache);
+    undef($current_symb);
+    undef($cache_filename);
+    return;
+}
+
+#####################################################
+#####################################################
+
+=pod
+
+=item &ensure_proper_cache($symb)
+
+Called to make sure we have the proper cache set up.  This is called
+prior to every answer lookup.
+
+=cut
+
+#####################################################
+#####################################################
+sub ensure_proper_cache {
+    my ($symb) = @_;
+    my $cid = $ENV{'request.course.id'};
+    my $new_filename =  '/home/httpd/perl/tmp/'.
+        'problemanalsysis_'.$cid.'answer_cache.db';
+    if (! defined($cache_filename) ||
+        $cache_filename ne $new_filename ||
+        ! defined($current_symb)   ||
+        $current_symb ne $symb) {
+        $cache_filename = $new_filename;
+        # Notice: $current_symb is not set to $symb until after the cache is
+        # loaded.  This is what tells &load_answer_cache to load in a new
+        # symb cache.
+        &load_answer_cache($symb);
+        $current_symb = $symb;
+    }
+}
+
+#####################################################
+#####################################################
+
+=pod
+
+=item &store_answer($sname,$sdom,$symb,$partid,$respid,$dataset)
+
+Stores the answer data in the in memory cache.
+
+=cut
+
+#####################################################
+#####################################################
+sub store_answer {
+    my ($sname,$sdom,$symb,$partid,$respid,$dataset) = @_;
+    return if ($symb ne $current_symb);
+    if (defined($partid)) {
+        if (defined($respid)) {
+            $cache{$sname.':'.$sdom}->{$partid}->{$respid} = $dataset;
+        } else {
+            $cache{$sname.':'.$sdom}->{$partid} = $dataset;
+        }
+    } else {
+        $cache{$sname.':'.$sdom}=$dataset;
+    }
+    return;
+}
+
+}
+#####################################################
+#####################################################
+
+=pod
+
+=back
+
+=cut
+
+#####################################################
+#####################################################
+
 ##
 ## The following is copied from datecalc1.pl, part of the 
 ## Spreadsheet::WriteExcel CPAN module.