Add function to reset LLM instance

Author: tobiasvonderheidt

app/src/main/java/org/vonderheidt/hips/ui/screens/HomeScreen.kt

@@ -57,6 +57,7 @@ import kotlinx.coroutines.launch
 import org.vonderheidt.hips.navigation.Screen
 import org.vonderheidt.hips.ui.theme.HiPSTheme
 import org.vonderheidt.hips.utils.LLM
+import org.vonderheidt.hips.utils.LlamaCpp
 import org.vonderheidt.hips.utils.Steganography
 
 /**
@@ -254,6 +255,11 @@ fun HomeScreen(navController: NavController, modifier: Modifier) {
                     // Use Dispatchers.Default since LLM inference is CPU-bound
                     // Keep encapsulation of coroutine vs if-else like this so the loading animation works
                     CoroutineScope(Dispatchers.Default).launch {
+                        // Reset LLM instance on every button press to ensure reproducibility, otherwise ctx before encode and decode would not be the same
+                        // Works when called before this coroutine or inside it, but crashes when called inside its own coroutine before this one
+                        // Might be desirable to use it with Dispatchers.IO as it is presumably I/O-bound, but seems negligible
+                        LlamaCpp.resetInstance()
+
                         if (selectedMode == 0) {
                             coverText = Steganography.encode(context, secretMessage)
                         }

app/src/main/java/org/vonderheidt/hips/utils/LlamaCpp.kt

@@ -74,6 +74,27 @@ object LlamaCpp {
         }
     }
 
+    /**
+     * Function to reset the instance of the LLM in a thread-safe manner.
+     *
+     * Needed to ensure reproducible results when switching between encode/decode mode or when encoding/decoding multiple times sequentially.
+     */
+    fun resetInstance() {
+        // Mirrors startInstance
+        if (ctx == 0L) {
+            return
+        }
+
+        synchronized(this) {
+            if (ctx != 0L) {
+                unloadCtx()
+                ctx = 0L
+
+                ctx = loadCtx()
+            }
+        }
+    }
+
     /**
      * Function to check if a token is the end of a sentence. Needed to complete the last sentence of the cover text.
      *