suffix_sorting: fixed termination condition in prefix quadrupling

bingmann · Apr 25, 2016 · 7d49440 · 7d49440
1 parent 18e5d1d
commit 7d49440
Showing 1 changed file with 48 additions and 21 deletions.
diff --git a/examples/suffix_sorting/prefix_quadrupling.cpp b/examples/suffix_sorting/prefix_quadrupling.cpp
@@ -604,8 +604,6 @@ DIA<Index> PrefixQuadrupling(const InputDIA& input_dia, size_t input_size) {
             })
         .Sort();
 
-    // chars_sorted.Keep().Print("Test");
-
     auto names =
         chars_sorted
         .template FlatWindow<IndexRank>(
@@ -617,13 +615,37 @@ DIA<Index> PrefixQuadrupling(const InputDIA& input_dia, size_t input_size) {
                     emit(IndexRank { rb[1].index, Index(0) });
                 else
                     emit(IndexRank { rb[1].index, Index(index + 2) });
+            });
+
+    auto number_duplicates =
+        names.Keep()
+        .Filter([](const IndexRank& ir) {
+                return ir.rank == Index(0);
             })
-        .PrefixSum([](const IndexRank& a, const IndexRank& b) {
-                       return IndexRank {
-                           b.index,
-                           (a.rank > b.rank ? a.rank : b.rank)
-                       };
-                   });
+        .Size();
+
+    if (number_duplicates == 0) {
+        if (input_dia.context().my_rank() == 0)
+            sLOG1 << "Finished before doubling in loop";
+
+        auto sa =
+            names
+            .Map([](const IndexRank& ir) {
+                     return ir.index;
+                 });
+
+        return sa.Collapse();
+    }
+
+    names =
+        names
+        .PrefixSum(
+            [](const IndexRank& a, const IndexRank& b) {
+                return IndexRank { b.index, std::max(a.rank, b.rank) };
+            });
+
+    if (debug_print)
+        names.Keep().Print("names before loop");
 
     size_t iteration = 1;
     while (true) {
@@ -680,25 +702,21 @@ DIA<Index> PrefixQuadrupling(const InputDIA& input_dia, size_t input_size) {
                         emit(IndexRank { rb[1].index, Index(0) });
                     else
                         emit(IndexRank { rb[1].index, Index(1) });
-                })
-            .PrefixSum([](const IndexRank& a, const IndexRank& b) {
-                           return IndexRank { b.index, a.rank + b.rank };
-                       });
+                });
 
-        auto max_rank =
+        number_duplicates =
             names.Keep()
-            .Map([](const IndexRank& ir) {
-                     return ir.rank;
-                 })
-            .Max();
+            .Filter([](const IndexRank& ir) {
+                    return ir.rank == Index(0);
+                })
+            .Size();
 
         if (input_dia.context().my_rank() == 0) {
-            sLOG1 << "iteration" << iteration
-                  << "max_rank" << max_rank
-                  << "duplicates" << input_size - max_rank;
+            sLOG1 << "iteration" << iteration - 1
+                  << "duplicates" << number_duplicates;
         }
 
-        if (max_rank == input_size) {
+        if (number_duplicates == 0) {
             auto sa =
                 names
                 .Map([](const IndexRank& ir) {
@@ -707,6 +725,15 @@ DIA<Index> PrefixQuadrupling(const InputDIA& input_dia, size_t input_size) {
 
             return sa.Collapse();
         }
+
+        names =
+            names
+            .PrefixSum([](const IndexRank& a, const IndexRank& b) {
+                           return IndexRank { b.index, std::max(a.rank, b.rank) };
+                       });
+
+        if (debug_print)
+            names.Keep().Print("names");
     }
 }