Add thin Minisketch wrapper to pick best implementation

1 files changed, 77 insertions, 0 deletions

diff --git a/src/minisketchwrapper.cpp b/src/minisketchwrapper.cpp
new file mode 100644
index 0000000000..fb176fb153
--- /dev/null
+++ b/src/minisketchwrapper.cpp
@@ -0,0 +1,77 @@
+// Copyright (c) 2021 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#include <minisketchwrapper.h>
+
+#include <logging.h>
+#include <util/time.h>
+
+#include <minisketch.h>
+
+#include <algorithm>
+#include <cstddef>
+#include <cstdint>
+#include <optional>
+#include <utility>
+#include <vector>
+
+namespace {
+
+static constexpr uint32_t BITS = 32;
+
+uint32_t FindBestImplementation()
+{
+    std::optional<std::pair<int64_t, uint32_t>> best;
+
+    uint32_t max_impl = Minisketch::MaxImplementation();
+    for (uint32_t impl = 0; impl <= max_impl; ++impl) {
+        std::vector<int64_t> benches;
+        uint64_t offset = 0;
+        /* Run a little benchmark with capacity 32, adding 184 entries, and decoding 11 of them once. */
+        for (int b = 0; b < 11; ++b) {
+            if (!Minisketch::ImplementationSupported(BITS, impl)) break;
+            Minisketch sketch(BITS, impl, 32);
+            auto start = GetTimeMicros();
+            for (uint64_t e = 0; e < 100; ++e) {
+                sketch.Add(e*1337 + b*13337 + offset);
+            }
+            for (uint64_t e = 0; e < 84; ++e) {
+                sketch.Add(e*1337 + b*13337 + offset);
+            }
+            offset += (*sketch.Decode(32))[0];
+            auto stop = GetTimeMicros();
+            benches.push_back(stop - start);
+        }
+        /* Remember which implementation has the best median benchmark time. */
+        if (!benches.empty()) {
+            std::sort(benches.begin(), benches.end());
+            if (!best || best->first > benches[5]) {
+                best = std::make_pair(benches[5], impl);
+            }
+        }
+    }
+    assert(best.has_value());
+    LogPrintf("Using Minisketch implementation number %i\n", best->second);
+    return best->second;
+}
+
+uint32_t Minisketch32Implementation()
+{
+    // Fast compute-once idiom.
+    static uint32_t best = FindBestImplementation();
+    return best;
+}
+
+} // namespace
+
+
+Minisketch MakeMinisketch32(size_t capacity)
+{
+    return Minisketch(BITS, Minisketch32Implementation(), capacity);
+}
+
+Minisketch MakeMinisketch32FP(size_t max_elements, uint32_t fpbits)
+{
+    return Minisketch::CreateFP(BITS, Minisketch32Implementation(), max_elements, fpbits);
+}