diff --git a/chatglm.cpp b/chatglm.cpp
index 3cac2a4..daaa26a 100644
--- a/chatglm.cpp
+++ b/chatglm.cpp
@@ -14,7 +14,6 @@
 #include <string>
 #include <sys/stat.h>
 #include <thread>
-#include <unordered_set>
 
 #ifdef __has_include
 #if __has_include(<unistd.h>)
@@ -589,19 +588,19 @@ int BaseModelForCausalLM::generate_next_token(const std::vector<int> &input_ids,
 void BaseModelForCausalLM::sampling_repetition_penalty(float *first, float *last, const std::vector<int> &input_ids,
                                                        float penalty) {
     CHATGLM_CHECK(penalty > 0) << "penalty must be a positive float, but got " << penalty;
-    std::unordered_set<int> unique_input_ids(input_ids.begin(), input_ids.end());
-    for (int id : unique_input_ids) {
-        CHATGLM_CHECK(first <= first + id && first + id < last) << "invalid input id " << id;
-        if (first[id] > 0) {
-            first[id] /= penalty;
-        } else {
-            first[id] *= penalty;
+    const float inv_penalty = 1.f / penalty;
+    const int vocab_size = last - first;
+    std::vector<bool> occurrence(vocab_size, false);
+    for (const int id : input_ids) {
+        if (!occurrence[id]) {
+            first[id] *= (first[id] > 0) ? inv_penalty : penalty;
         }
+        occurrence[id] = true;
     }
 }
 
 void BaseModelForCausalLM::sampling_temperature(float *first, float *last, float temp) {
-    float inv_temp = 1.f / temp;
+    const float inv_temp = 1.f / temp;
     for (float *it = first; it != last; it++) {
         *it *= inv_temp;
     }
@@ -616,12 +615,12 @@ TokenIdScore *BaseModelForCausalLM::sampling_top_p(TokenIdScore *first, TokenIdS
     sampling_softmax_inplace(first, last);
 
     while (first + 1 < last) {
-        float pivot_score = (last - 1)->score; // use mid score?
+        const float pivot_score = (last - 1)->score; // use mid score?
         TokenIdScore *mid =
             std::partition(first, last - 1, [pivot_score](const TokenIdScore &x) { return x.score > pivot_score; });
         std::swap(*mid, *(last - 1));
 
-        float prefix_sum =
+        const float prefix_sum =
             std::accumulate(first, mid, 0.f, [](float sum, const TokenIdScore &x) { return sum + x.score; });
         if (prefix_sum >= top_p) {
             last = mid;
diff --git a/chatglm_cpp/__init__.py b/chatglm_cpp/__init__.py
index d3938bd..cdb79cd 100644
--- a/chatglm_cpp/__init__.py
+++ b/chatglm_cpp/__init__.py
@@ -6,7 +6,7 @@
 import chatglm_cpp._C as _C
 from chatglm_cpp._C import ChatMessage
 
-__version__ = "0.3.0"
+__version__ = "0.3.1.dev"
 
 
 @dataclass
diff --git a/chatglm_test.cpp b/chatglm_test.cpp
index 03b8cd5..6295a3e 100644
--- a/chatglm_test.cpp
+++ b/chatglm_test.cpp
@@ -36,6 +36,8 @@ static inline char *read_tensor_data(char *ptr, ggml_tensor *tensor) {
 
 static inline float random() { return rand() / (float)RAND_MAX; }
 
+static inline float random(float lo, float hi) { return lo + random() * (hi - lo); }
+
 static inline void random_fill(ggml_tensor *tensor) {
     std::vector<float> values(ggml_nelements(tensor));
     for (float &v : values) {
@@ -115,6 +117,28 @@ TEST(Sampling, RepetitionPenalty) {
     }
 }
 
+TEST(DISABLED_Sampling, BenchmarkRepetitionPenalty) {
+    const float penalty = 1.2;
+    constexpr size_t vocab_size = 128000;
+    constexpr int seq_len = 32000;
+    std::vector<float> logits(vocab_size);
+    for (auto &x : logits) {
+        x = random(-1, 1);
+    }
+    std::vector<int> input_ids(seq_len);
+    for (size_t i = 0; i < input_ids.size(); i++) {
+        input_ids[i] = i;
+    }
+
+    auto fn = [&logits, &input_ids, penalty] {
+        BaseModelForCausalLM::sampling_repetition_penalty(logits.data(), logits.data() + logits.size(), input_ids,
+                                                          penalty);
+    };
+    auto elapsed_ms = timeit(fn, 2, 100);
+    std::cout << "[" << ::testing::UnitTest::GetInstance()->current_test_info()->name() << "] " << elapsed_ms
+              << " ms\n";
+}
+
 TEST(Sampling, Temperature) {
     constexpr float temp = 0.7;
     std::vector<float> logits(64);