diff --git a/core/src/main/kotlin/org/evomaster/core/problem/rest/classifier/probabilistic/AbstractProbabilistic400EndpointModel.kt b/core/src/main/kotlin/org/evomaster/core/problem/rest/classifier/probabilistic/AbstractProbabilistic400EndpointModel.kt
index dbf1972f6a..bc52e2665d 100644
--- a/core/src/main/kotlin/org/evomaster/core/problem/rest/classifier/probabilistic/AbstractProbabilistic400EndpointModel.kt
+++ b/core/src/main/kotlin/org/evomaster/core/problem/rest/classifier/probabilistic/AbstractProbabilistic400EndpointModel.kt
@@ -82,6 +82,12 @@ abstract class AbstractProbabilistic400EndpointModel(
             return
         }
 
+        if (modelKeys != null && dimension != null) {
+            require(warmup > 0) { "Warmup must be positive" }
+            initialized = true
+            return
+        }
+
         val encoder = InputEncoderUtilWrapper(input, encoderType = encoderType)
         val allParamsPathsAndEncodedValues = encoder.getAllParamsPathsAndEncodedValues()
 
diff --git a/core/src/main/kotlin/org/evomaster/core/problem/rest/classifier/probabilistic/InputEncoderUtilWrapper.kt b/core/src/main/kotlin/org/evomaster/core/problem/rest/classifier/probabilistic/InputEncoderUtilWrapper.kt
index ede4265ec5..de642d89a2 100644
--- a/core/src/main/kotlin/org/evomaster/core/problem/rest/classifier/probabilistic/InputEncoderUtilWrapper.kt
+++ b/core/src/main/kotlin/org/evomaster/core/problem/rest/classifier/probabilistic/InputEncoderUtilWrapper.kt
@@ -23,6 +23,7 @@ import org.evomaster.core.search.gene.numeric.NumberGene
 import org.evomaster.core.search.gene.string.StringGene
 import kotlin.math.sqrt
 import kotlin.reflect.KClass
+import java.util.IdentityHashMap
 
 /**
  * Utility object for encoding the genes of a [org.evomaster.core.problem.rest.data.RestCallAction] into a numerical representation.
@@ -79,24 +80,22 @@ class InputEncoderUtilWrapper(
      * Builds a string representing the gene name and all its parents.
      * This string is used as a unique identifier for the gene in the AI models.
      */
-    private fun genePath(g: Gene): String {
-
-        val names = mutableListOf<String>()
+    private val _genePathCache = IdentityHashMap<Gene, String>()
 
-        var current: Gene? = g
-
-        while (current != null) {
-            names.add(current.name)
-            current = current.parent as? Gene
+    private fun genePath(g: Gene): String {
+        return _genePathCache.getOrPut(g) {
+            val names = mutableListOf<String>()
+            var current: Gene? = g
+            while (current != null) {
+                names.add(current.name)
+                current = current.parent as? Gene
+            }
+            val path = names.reversed()
+            if (path.size > 1)
+                path.dropLast(1).joinToString("/")
+            else
+                path.joinToString("/")
         }
-
-        val path = names.reversed()
-        
-        return if (path.size > 1)
-            path.dropLast(1).joinToString("/") //ignore the last name, which is the repetition of gene itself as its own parent
-        else
-            path.joinToString("/")
-
     }
 
     /**
@@ -127,8 +126,9 @@ class InputEncoderUtilWrapper(
      */
     fun getAllParamsPathsAndEncodedValues(): Map<String, Double> {
 
-        val paramPaths = endPointToGeneList().map { it.paramPath }
-        val encodedValues = encode()
+        val geneList = endPointToGeneList()
+        val paramPaths = geneList.map { it.paramPath }
+        val encodedValues = encode(geneList)
 
         return paramPaths.zip(encodedValues).toMap()
     }
@@ -186,10 +186,10 @@ class InputEncoderUtilWrapper(
      *
      * @return a list of doubles representing the encoded feature vector
      */
-    fun encode(): List<Double> {
+    fun encode(geneList: List<ParamAndGene> = endPointToGeneList()): List<Double> {
         val sentinel = -1e6 // for null handling
         val neutral = 0.0 // for handling unsupported genes
-        val listGenes = endPointToGeneList().map { it.gene }
+        val listGenes = geneList.map { it.gene }
         val rawEncodedFeatures = mutableListOf<Double>()
 
         for (g in listGenes) {