main: add progress spinner on context swap

examples/main/main.cpp

@@ -5,6 +5,7 @@
 #include "build-info.h"
 #include "grammar-parser.h"
 
+#include <atomic>
 #include <cassert>
 #include <cinttypes>
 #include <cmath>
@@ -15,6 +16,7 @@
 #include <iostream>
 #include <sstream>
 #include <string>
+#include <thread>
 #include <vector>
 
 #if defined (__unix__) || (defined (__APPLE__) && defined (__MACH__))
@@ -40,6 +42,7 @@ static std::vector<llama_token> * g_input_tokens;
 static std::ostringstream       * g_output_ss;
 static std::vector<llama_token> * g_output_tokens;
 static bool is_interacting = false;
+static std::atomic<bool> is_swapping(false); // for spinner progress indicator
 
 void write_logfile(
     const llama_context * ctx, const gpt_params & params, const llama_model * model,
@@ -85,6 +88,15 @@ void write_logfile(
     fclose(logfile);
 }
 
+void display_spinner() {
+    const char spinner[] = { '/', '-', '\\', '|' };
+    size_t i = 0;
+    while (is_swapping) {
+        std::cerr << spinner[i++ % sizeof(spinner)] << '\b';
+        std::this_thread::sleep_for(std::chrono::milliseconds(125));
+    }
+}
+
 #if defined (__unix__) || (defined (__APPLE__) && defined (__MACH__)) || defined (_WIN32)
 void sigint_handler(int signo) {
     if (signo == SIGINT) {
@@ -523,6 +535,8 @@ int main(int argc, char ** argv) {
                     break;
                 }
 
+                is_swapping = true; // enable spinner
+
                 const int n_left = n_past - params.n_keep;
                 LOG("context full, swapping: n_past = %d, n_left = %d, n_ctx = %d, n_keep = %d\n", n_past, n_left, n_ctx, params.n_keep);
 
@@ -541,6 +555,8 @@ int main(int argc, char ** argv) {
                 path_session.clear();
             }
 
+            std::thread spinner_thread(display_spinner);
+
             // try to reuse a matching prefix from the loaded session instead of re-eval (via n_past)
             if (n_session_consumed < (int) session_tokens.size()) {
                 size_t i = 0;
@@ -626,6 +642,10 @@ int main(int argc, char ** argv) {
                 session_tokens.insert(session_tokens.end(), embd.begin(), embd.end());
                 n_session_consumed = session_tokens.size();
             }
+
+            // Disable spinner
+            is_swapping = false;
+            spinner_thread.join();
         }
 
         embd.clear();