From 73002dc0489d91f90ba3dcf3532e33b932c93d58 Mon Sep 17 00:00:00 2001
From: Roman Gershman <roman@dragonflydb.io>
Date: Sun, 29 Sep 2024 09:04:25 +0300
Subject: [PATCH] chore: add a benchmark comparing lpStringToInt64 to
 SimpleAtoi (#3815)

Seems that lpStringToInt64 is fairly optimized.
On c7g:

```
BM_LpString2Int/1      27383 ns        27381 ns       204149
BM_LpString2Int/2      24535 ns        24534 ns       227981
```

so SimpleAtoi has only ~10% improvement.

Signed-off-by: Roman Gershman <roman@dragonflydb.io>
---
 src/core/compact_object_test.cc | 26 ++++++++++++++++++++++++--
 1 file changed, 24 insertions(+), 2 deletions(-)

diff --git a/src/core/compact_object_test.cc b/src/core/compact_object_test.cc
index 6dfd485ac..bff60e3f4 100644
--- a/src/core/compact_object_test.cc
+++ b/src/core/compact_object_test.cc
@@ -761,7 +761,7 @@ static void BM_UnpackSimd(benchmark::State& state) {
 BENCHMARK(BM_UnpackSimd);
 
 static void BM_LpCompare(benchmark::State& state) {
-  std::random_device rd;
+  std::mt19937_64 rd;
   uint8_t* lp = lpNew(0);
   for (unsigned i = 0; i < 100; ++i) {
     lp = lpAppendInteger(lp, rd() % (1ULL << 48));
@@ -780,7 +780,7 @@ static void BM_LpCompare(benchmark::State& state) {
 BENCHMARK(BM_LpCompare);
 
 static void BM_LpCompareInt(benchmark::State& state) {
-  std::random_device rd;
+  std::mt19937_64 rd;
   uint8_t* lp = lpNew(0);
   for (unsigned i = 0; i < 100; ++i) {
     lp = lpAppendInteger(lp, rd() % (1ULL << 48));
@@ -832,4 +832,26 @@ static void BM_LpGet(benchmark::State& state) {
 }
 BENCHMARK(BM_LpGet)->Arg(1)->Arg(2);
 
+extern "C" int lpStringToInt64(const char* s, unsigned long slen, int64_t* value);
+
+static void BM_LpString2Int(benchmark::State& state) {
+  int version = state.range(0);
+  std::mt19937_64 rd;
+  vector<string> values;
+  for (unsigned i = 0; i < 1000; ++i) {
+    int64_t val = rd();
+    values.push_back(absl::StrCat(val));
+  }
+
+  int64_t ival = 0;
+  while (state.KeepRunning()) {
+    for (const auto& val : values) {
+      int res = version == 1 ? lpStringToInt64(val.data(), val.size(), &ival)
+                             : absl::SimpleAtoi(val, &ival);
+      benchmark::DoNotOptimize(res);
+    }
+  }
+}
+BENCHMARK(BM_LpString2Int)->Arg(1)->Arg(2);
+
 }  // namespace dfly