Start reimplementing the TurboPFor decoding functions.

[plocate] / bench.cpp

diff --git a/bench.cpp b/bench.cpp
new file mode 100644 (file)
index 0000000..46b6ed0
--- /dev/null
+++ b/bench.cpp
@@ -0,0 +1,88 @@
+#include <stdio.h>
+#include <unistd.h>
+#include <fcntl.h>
+#include <chrono>
+#include <memory>
+
+#define dprintf(...)
+//#define dprintf(...) fprintf(stderr, __VA_ARGS__);
+
+#include "turbopfor.h"
+#include "vp4.h"
+#include "db.h"
+#include "io_uring_engine.h"
+
+using namespace std;
+using namespace std::chrono;
+
+int main(void)
+{
+       int fd = open("plocate.db", O_RDONLY);
+       if (fd == -1) {
+               perror("plocate.db");
+               exit(1);
+       }
+
+       Header hdr;
+       complete_pread(fd, &hdr, sizeof(hdr), /*offset=*/0);
+
+       unique_ptr<Trigram[]> ht(new Trigram[hdr.hashtable_size + hdr.extra_ht_slots + 1]);
+       complete_pread(fd, ht.get(), (hdr.hashtable_size + hdr.extra_ht_slots + 1) * sizeof(Trigram), hdr.hash_table_offset_bytes);
+
+       uint32_t longest_pl = 0;
+       vector<pair<string, unsigned>> posting_lists;
+       for (unsigned i = 0; i < hdr.hashtable_size + hdr.extra_ht_slots; ++i) {
+               if (ht[i].num_docids == 0) {
+                       continue;
+               }
+               size_t len = ht[i + 1].offset - ht[i].offset;
+               string str;
+               str.resize(len);
+               complete_pread(fd, &str[0], len, ht[i].offset);
+               posting_lists.emplace_back(move(str), ht[i].num_docids);
+               longest_pl = std::max(ht[i].num_docids, longest_pl);
+       }
+       ht.reset();
+       fprintf(stderr, "Read %zu posting lists.\n", posting_lists.size());
+
+       size_t num_errors = 0;
+       for (auto &[pl, num_docids] : posting_lists) {
+               //fprintf(stderr, "%zu bytes, %u docids\n", pl.size(), num_docids);
+               vector<uint32_t> out1, out2;
+               out1.resize(num_docids + 128);
+               out2.resize(num_docids + 128);
+               unsigned char *pldata = reinterpret_cast<unsigned char *>(&pl[0]);
+               p4nd1dec32(pldata, num_docids, &out1[0]);
+               decode_pfor_delta1<128>(pldata, num_docids, &out2[0]);
+               for (unsigned i = 0; i < num_docids; ++i) {
+                       if (out1[i] != out2[i]) {
+                               for (unsigned j = 0; j < num_docids; ++j) {
+                                       fprintf(stderr, "%3u: reference=%u ours=%u  (diff=%d)\n", j, out1[j], out2[j], out1[j] - out2[j]);
+                               }
+                               ++num_errors;
+                               break;
+                       }
+               }
+       }
+       fprintf(stderr, "%zu/%zu posting lists had errors in decoding.\n", num_errors, posting_lists.size());
+
+       vector<uint32_t> dummy;
+       dummy.resize(longest_pl + 128);
+       steady_clock::time_point start = steady_clock::now();
+       for (auto &[pl, num_docids] : posting_lists) {
+               unsigned char *pldata = reinterpret_cast<unsigned char *>(&pl[0]);
+               p4nd1dec32(pldata, num_docids, &dummy[0]);
+       }
+       steady_clock::time_point end = steady_clock::now();
+       double reference_sec = duration<double>(end - start).count();
+       fprintf(stderr, "Decoding with reference implementation: %.1f ms\n", 1e3 * reference_sec);
+
+       start = steady_clock::now();
+       for (auto &[pl, num_docids] : posting_lists) {
+               unsigned char *pldata = reinterpret_cast<unsigned char *>(&pl[0]);
+               decode_pfor_delta1<128>(pldata, num_docids, &dummy[0]);
+       }
+       end = steady_clock::now();
+       double own_sec = duration<double>(end - start).count();
+       fprintf(stderr, "Decoding with own implementation: %.1f ms (%.2f%% speed)\n", 1e3 * own_sec, 100.0 * reference_sec / own_sec);
+}