[Continuous batching] Replace standard max_element call with custom l…

…oop for greedy sampling (#607)

Searching for max element in a custom loop gives better performance than
using std::max_element

src/cpp/src/sampler.hpp

@@ -219,8 +219,13 @@ class Sampler {
     }
 
     Token _greedy_sample(const std::vector<Token>& logit_vector) const {
-        auto out_token = std::max_element(logit_vector.begin(), logit_vector.end(), [](const Token& lhs, const Token& rhs) { return lhs.m_log_prob < rhs.m_log_prob; });
-        return *out_token;
+        Token max_token{-std::numeric_limits<float>::infinity() , 0};
+        for (const auto& logit : logit_vector) {
+            if (logit.m_log_prob > max_token.m_log_prob) {
+                max_token = logit;
+            }
+        }
+        return max_token;
     }
 
     std::vector<Token> _multinomial_sample(const std::vector<Token>& logit_vector, size_t num_tokens_per_sequence) {