diff -r 6f63f5ed3cab -r be77fb2da242 src/ucx/map.h
--- a/src/ucx/map.h	Thu Dec 19 18:47:23 2019 +0100
+++ b/src/ucx/map.h	Thu Dec 19 19:58:41 2019 +0100
@@ -124,7 +124,7 @@
 /** Structure for an iterator over a UcxMap. */
 struct UcxMapIterator {
     /** The map to iterate over. */
-    UcxMap        *map;
+    UcxMap const  *map;
     
     /** The current map element. */
     UcxMapElement *cur;
@@ -211,7 +211,7 @@
  * @param data additional data for the copy function
  * @return 0 on success or a non-zero value on memory allocation errors
  */
-int ucx_map_copy(UcxMap *from, UcxMap *to, copy_func fnc, void *data);
+int ucx_map_copy(UcxMap const *from, UcxMap *to, copy_func fnc, void *data);
 
 /**
  * Clones the map and rehashes if necessary.
@@ -227,7 +227,25 @@
  * @return the cloned map
  * @see ucx_map_copy()
  */
-UcxMap *ucx_map_clone(UcxMap *map, copy_func fnc, void *data);
+UcxMap *ucx_map_clone(UcxMap const *map, copy_func fnc, void *data);
+
+/**
+ * Clones the map and rehashes if necessary.
+ *
+ * <b>Note:</b> In contrast to ucx_map_rehash() the load factor is irrelevant.
+ * This function <i>always</i> ensures a new UcxMap.size of at least
+ * 2.5*UcxMap.count.
+ *
+ * @param allocator the allocator to use for the cloned map
+ * @param map the map to clone
+ * @param fnc the copy function to use or <code>NULL</code> if the new and
+ * the old map shall share the data pointers
+ * @param data additional data for the copy function
+ * @return the cloned map
+ * @see ucx_map_copy()
+ */
+UcxMap *ucx_map_clone_a(UcxAllocator *allocator,
+                        UcxMap const *map, copy_func fnc, void *data);
 
 /**
  * Increases size of the hash map, if necessary.
@@ -264,7 +282,7 @@
  * @param key the key
  * @return the value
  */
-void* ucx_map_get(UcxMap *map, UcxKey key);
+void* ucx_map_get(UcxMap const *map, UcxKey key);
 
 /**
  * Removes a key/value-pair from the map by using the key.
@@ -406,7 +424,7 @@
  * first element list
  * @see ucx_map_iter_next()
  */
-UcxMapIterator ucx_map_iterator(UcxMap *map);
+UcxMapIterator ucx_map_iterator(UcxMap const *map);
 
 /**
  * Proceeds to the next element of the map (if any).
@@ -426,6 +444,102 @@
  */
 int ucx_map_iter_next(UcxMapIterator *iterator, UcxKey *key, void **value);
 
+/**
+ * Returns the union of two maps.
+ *
+ * The union is a fresh map which is filled by two successive calls of
+ * ucx_map_copy() on the two input maps.
+ *
+ * @param first the first source map
+ * @param second the second source map
+ * @param cpfnc a function to copy the elements
+ * @param cpdata additional data for the copy function
+ * @return a new map containing the union
+ */
+UcxMap* ucx_map_union(const UcxMap *first, const UcxMap *second,
+                      copy_func cpfnc, void* cpdata);
+
+/**
+ * Returns the union of two maps.
+ *
+ * The union is a fresh map which is filled by two successive calls of
+ * ucx_map_copy() on the two input maps.
+ *
+ * @param allocator the allocator that shall be used by the new map
+ * @param first the first source map
+ * @param second the second source map
+ * @param cpfnc a function to copy the elements
+ * @param cpdata additional data for the copy function
+ * @return a new map containing the union
+ */
+UcxMap* ucx_map_union_a(UcxAllocator *allocator,
+                        const UcxMap *first, const UcxMap *second,
+                        copy_func cpfnc, void* cpdata);
+
+/**
+ * Returns the intersection of two maps.
+ *
+ * The intersection is defined as a copy of the first map with every element
+ * removed that has no valid key in the second map.
+ *
+ * @param first the first source map
+ * @param second the second source map
+ * @param cpfnc a function to copy the elements
+ * @param cpdata additional data for the copy function
+ * @return a new map containing the intersection
+ */
+UcxMap* ucx_map_intersection(const UcxMap *first, const UcxMap *second,
+                             copy_func cpfnc, void* cpdata);
+
+/**
+ * Returns the intersection of two maps.
+ *
+ * The intersection is defined as a copy of the first map with every element
+ * removed that has no valid key in the second map.
+ *
+ * @param allocator the allocator that shall be used by the new map
+ * @param first the first source map
+ * @param second the second source map
+ * @param cpfnc a function to copy the elements
+ * @param cpdata additional data for the copy function
+ * @return a new map containing the intersection
+ */
+UcxMap* ucx_map_intersection_a(UcxAllocator *allocator,
+                               const UcxMap *first, const UcxMap *second,
+                               copy_func cpfnc, void* cpdata);
+
+/**
+ * Returns the difference of two maps.
+ *
+ * The difference contains a copy of all elements of the first map
+ * for which the corresponding keys cannot be found in the second map.
+ *
+ * @param first the first source map
+ * @param second the second source map
+ * @param cpfnc a function to copy the elements
+ * @param cpdata additional data for the copy function
+ * @return a new list containing the difference
+ */
+UcxMap* ucx_map_difference(const UcxMap *first, const UcxMap *second,
+                           copy_func cpfnc, void* cpdata);
+
+/**
+ * Returns the difference of two maps.
+ *
+ * The difference contains a copy of all elements of the first map
+ * for which the corresponding keys cannot be found in the second map.
+ *
+ * @param allocator the allocator that shall be used by the new map
+ * @param first the first source map
+ * @param second the second source map
+ * @param cpfnc a function to copy the elements
+ * @param cpdata additional data for the copy function
+ * @return a new list containing the difference
+ */
+UcxMap* ucx_map_difference_a(UcxAllocator *allocator,
+                             const UcxMap *first, const UcxMap *second,
+                             copy_func cpfnc, void* cpdata);
+
 
 #ifdef	__cplusplus
 }