From 22afd2c41777f68dfbc26af273da7e7c01319b86 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Wojciech=20Mu=C5=82a?= <wojciech_mula@poczta.onet.pl>
Date: Sun, 18 Feb 2018 17:13:54 +0100
Subject: [PATCH] Another sequantial variant

---
 .../SequentialAndZeroTracking.h               | 66 +++++++++++++++++++
 parallel-and-bitmaps/bitvector.h              |  6 ++
 parallel-and-bitmaps/main.cpp                 | 10 ++-
 3 files changed, 79 insertions(+), 3 deletions(-)
 create mode 100644 parallel-and-bitmaps/SequentialAndZeroTracking.h

diff --git a/parallel-and-bitmaps/SequentialAndZeroTracking.h b/parallel-and-bitmaps/SequentialAndZeroTracking.h
new file mode 100644
index 0000000..db8cccc
--- /dev/null
+++ b/parallel-and-bitmaps/SequentialAndZeroTracking.h
@@ -0,0 +1,66 @@
+#pragma once
+
+#include <vector>
+#include "MultipleAndInterface.h"
+
+class SequentialAndZeroTracking: public MultipleAndInterface {
+
+protected:
+    std::vector<bitvector*> input;
+    std::vector<char> zero;
+    const size_t block_size = 64;
+
+public:
+    SequentialAndZeroTracking(const std::vector<bitvector*>& input_)
+        : input(input_) {
+     
+        assert(input.size() >= 2);
+
+        const size_t n = (input[0]->n + block_size - 1) / block_size;
+        zero.resize(n);
+    }
+
+    virtual std::unique_ptr<bitvector> calculate() override {
+
+        bitvector* bv = new bitvector(*input[0]);
+
+#if 0
+#   define TRACE(msg, ...) printf(msg, __VA_ARGS__)
+#else
+#   define TRACE(msg, ...)
+#endif
+
+        size_t zero_blocks = 0;
+        for (size_t i=1; i < input.size(); i++) {
+            TRACE("bitmap %lu of %lu\n", i, input.size() - 1);
+            for (size_t j=0; j < zero.size(); j++) {
+                if (zero[j]) {
+                    continue; // skip zero block
+                }
+
+                const size_t start = j * block_size;
+                const size_t end   = std::min(start + block_size, bv->n);
+
+                uint64_t nonzero = 0;
+                for (size_t p=start; p < end; p++) {
+                    bv->data[p] &= input[i]->data[p];
+                    nonzero |= bv->data[p];
+                }
+
+                if (nonzero == 0) {
+                    // the block is zero, skip in the future
+                    TRACE("\tblock %lu will be skip\n", j);
+                    zero[j] = 1;
+                    zero_blocks += 1;
+                }
+            }
+
+            if (zero_blocks == zero.size()) {
+                TRACE("early exit after processing bitmap %lu\n", i);
+                break; // all blocks are zero
+            }
+        }
+
+        return std::unique_ptr<bitvector>(bv);
+    }
+};
diff --git a/parallel-and-bitmaps/bitvector.h b/parallel-and-bitmaps/bitvector.h
index 29d3fda..036a22d 100644
--- a/parallel-and-bitmaps/bitvector.h
+++ b/parallel-and-bitmaps/bitvector.h
@@ -2,6 +2,7 @@
 
 #include <cstdint>
 #include <cstdlib>
+#include <cstring>
 #include <cassert>
 
 class bitvector {
@@ -16,6 +17,11 @@ class bitvector {
         data = new uint64_t[n];
     }
 
+    bitvector(const bitvector& bv) : bitvector(bv.n) {
+
+        memcpy(data, bv.data, n * sizeof(uint64_t));
+    }
+
     ~bitvector() {
         delete[] data;
     }
diff --git a/parallel-and-bitmaps/main.cpp b/parallel-and-bitmaps/main.cpp
index 09a3da4..ce97aa3 100644
--- a/parallel-and-bitmaps/main.cpp
+++ b/parallel-and-bitmaps/main.cpp
@@ -1,6 +1,7 @@
 #include <chrono>
 
 #include "SequentialAnd.h"
+#include "SequentialAndZeroTracking.h"
 #include "ParallelAndNaive.h"
 #include "ParallelAndSplit.h"
 
@@ -12,7 +13,7 @@ void test(const char* info, MultipleAndInterface& ma, const std::vector<bitvecto
 
     assert(input.size() >= 2);
 
-    printf("%-20s (%lu bitmaps): ", info, input.size());
+    printf("%-30s (%lu bitmaps): ", info, input.size());
     fflush(stdout);
 
     const auto t1 = Clock::now();
@@ -20,12 +21,12 @@ void test(const char* info, MultipleAndInterface& ma, const std::vector<bitvecto
     const auto t2 = Clock::now();
 
     const auto t_us = duration_cast<microseconds>(t2 - t1).count();
-    printf("%luus [cardinality=%lu]\n", t_us, res->cardinality());
+    printf("%10luus [cardinality=%lu]\n", t_us, res->cardinality());
 }
 
 int main() {
     
-    const size_t bitmap_size = 2000000;
+    const size_t bitmap_size = 1000000;
     const size_t count = 100;
 
     std::vector<bitvector*> input;
@@ -40,6 +41,9 @@ int main() {
     SequentialAnd seq(input);
     test("SequentialAnd", seq, input);
 
+    SequentialAndZeroTracking seq2(input);
+    test("SequentialAndZeroTracking", seq2, input);
+
     ParallelAndNaive par1(input, 4);
     test("ParallelAndNaive", par1, input);