From 6805b9242755c34b039489479d8e397e331fcd68 Mon Sep 17 00:00:00 2001
From: Jared Van Bortel <jared@nomic.ai>
Date: Wed, 15 Nov 2023 11:34:47 -0500
Subject: [PATCH] llama : restore prefix space in llama tokenizer (#4081)

---
 llama.cpp | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/llama.cpp b/llama.cpp
index 01522fdb4e74f..92c4536cb948e 100644
--- a/llama.cpp
+++ b/llama.cpp
@@ -6283,7 +6283,10 @@ static std::vector<llama_vocab::id> llama_tokenize_internal(const llama_vocab &
                         //  by modifying llm_tokenizer_x to operate with string offsets like pre-tokenizer
                         //  and passing 'add space prefix' as bool argument
                         //
-                        auto raw_text = (special ? "" : " ") + fragment.raw_text.substr(fragment.offset, fragment.length);
+                        auto raw_text = fragment.raw_text.substr(fragment.offset, fragment.length);
+                        if (&fragment == &fragment_buffer.front()) {
+                            raw_text = " " + raw_text; // prefix with space if the first token is not special
+                        }
 
 #ifdef PRETOKENIZERDEBUG
                         fprintf(stderr,"TT: (%ld %ld %ld) '%s'\n", raw_text.length(), fragment.offset, fragment.length, raw_text.c_str());