0.9.3.30:

  Cache the previous key used to access a hash table.  If the next key
  is EQ to the cached key (if any), we can avoid computing the hash
  function and performing a full lookup.  This speeds up the common
  retrieve/update/store idiom on hash table places.

diff --git a/src/code/hash-table.lisp b/src/code/hash-table.lisp
index db58433..d8f5e13 100644 (file)
--- a/src/code/hash-table.lisp
+++ b/src/code/hash-table.lisp
@@ -51,6 +51,9 @@
   ;; Index into the Next vector chaining together free slots in the KV
   ;; vector.
   (next-free-kv 0 :type index)
+  ;; A cache that is either nil or is an index into the hash table
+  ;; that should be checked first
+  (cache nil :type (or null index))
   ;; The index vector. This may be larger than the hash size to help
   ;; reduce collisions.
   (index-vector (missing-arg)

diff --git a/src/code/target-hash-table.lisp b/src/code/target-hash-table.lisp
index e4d0a32..d3a9bdb 100644 (file)
--- a/src/code/target-hash-table.lisp
+++ b/src/code/target-hash-table.lisp
@@ -432,33 +432,42 @@
           (rehash-without-growing hash-table))
          ((not (zerop (hash-table-needing-rehash hash-table)))
           (flush-needing-rehash hash-table)))
-   ;; Search for key in the hash table.
-   (multiple-value-bind (hashing eq-based)
-       (funcall (hash-table-hash-fun hash-table) key)
-     (declare (type hash hashing))
-     (let* ((index-vector (hash-table-index-vector hash-table))
-            (length (length index-vector))
-            (index (rem hashing length))
-            (next (aref index-vector index))
-            (table (hash-table-table hash-table))
-            (next-vector (hash-table-next-vector hash-table))
-            (hash-vector (hash-table-hash-vector hash-table))
-            (test-fun (hash-table-test-fun hash-table)))
-       (declare (type index index))
-       ;; Search next-vector chain for a matching key.
-       (if (or eq-based (not hash-vector))
-           (do ((next next (aref next-vector next)))
-               ((zerop next) (values default nil))
-             (declare (type index next))
-             (when (eq key (aref table (* 2 next)))
-               (return (values (aref table (1+ (* 2 next))) t))))
-           (do ((next next (aref next-vector next)))
-               ((zerop next) (values default nil))
-             (declare (type index next))
-             (when (and (= hashing (aref hash-vector next))
-                        (funcall test-fun key (aref table (* 2 next))))
-               ;; Found.
-               (return (values (aref table (1+ (* 2 next))) t)))))))))
+
+   ;; First check the cache.  Use EQ here for speed.
+   (let ((cache (hash-table-cache hash-table))
+         (table (hash-table-table hash-table)))
+          
+     (if (and cache (< cache (length table)) (eq (aref table cache) key))
+         (values (aref table (1+ cache)) t)
+
+       ;; Search for key in the hash table.
+       (multiple-value-bind (hashing eq-based)
+           (funcall (hash-table-hash-fun hash-table) key)
+         (declare (type hash hashing))
+         (let* ((index-vector (hash-table-index-vector hash-table))
+                (length (length index-vector))
+                (index (rem hashing length))
+                (next (aref index-vector index))
+                (next-vector (hash-table-next-vector hash-table))
+                (hash-vector (hash-table-hash-vector hash-table))
+                (test-fun (hash-table-test-fun hash-table)))
+           (declare (type index index))
+           ;; Search next-vector chain for a matching key.
+           (if (or eq-based (not hash-vector))
+               (do ((next next (aref next-vector next)))
+                   ((zerop next) (values default nil))
+                 (declare (type index next))
+                 (when (eq key (aref table (* 2 next)))
+                   (setf (hash-table-cache hash-table) (* 2 next))
+                   (return (values (aref table (1+ (* 2 next))) t))))
+             (do ((next next (aref next-vector next)))
+                 ((zerop next) (values default nil))
+               (declare (type index next))
+               (when (and (= hashing (aref hash-vector next))
+                          (funcall test-fun key (aref table (* 2 next))))
+                 ;; Found.
+                 (setf (hash-table-cache hash-table) (* 2 next))
+                 (return (values (aref table (1+ (* 2 next))) t)))))))))))
 
 ;;; so people can call #'(SETF GETHASH)
 (defun (setf gethash) (new-value key table &optional default)
@@ -480,64 +489,75 @@
          ((not (zerop (hash-table-needing-rehash hash-table)))
           (flush-needing-rehash hash-table)))
 
-   ;; Search for key in the hash table.
-   (multiple-value-bind (hashing eq-based)
-       (funcall (hash-table-hash-fun hash-table) key)
-     (declare (type hash hashing))
-     (let* ((index-vector (hash-table-index-vector hash-table))
-            (length (length index-vector))
-            (index (rem hashing length))
-            (next (aref index-vector index))
-            (kv-vector (hash-table-table hash-table))
-            (next-vector (hash-table-next-vector hash-table))
-            (hash-vector (hash-table-hash-vector hash-table))
-            (test-fun (hash-table-test-fun hash-table)))
-       (declare (type index index))
-
-       (cond ((or eq-based (not hash-vector))
-              (when eq-based
-                (set-header-data kv-vector sb!vm:vector-valid-hashing-subtype))
-
-              ;; Search next-vector chain for a matching key.
-              (do ((next next (aref next-vector next)))
-                  ((zerop next))
-                (declare (type index next))
-                (when (eq key (aref kv-vector (* 2 next)))
-                  ;; Found, just replace the value.
-                  (setf (aref kv-vector (1+ (* 2 next))) value)
-                  (return-from %puthash value))))
-             (t
-              ;; Search next-vector chain for a matching key.
-              (do ((next next (aref next-vector next)))
-                  ((zerop next))
-                (declare (type index next))
-                (when (and (= hashing (aref hash-vector next))
-                           (funcall test-fun key
-                                    (aref kv-vector (* 2 next))))
-                  ;; Found, just replace the value.
-                  (setf (aref kv-vector (1+ (* 2 next))) value)
-                  (return-from %puthash value)))))
-
-       ;; Pop a KV slot off the free list
-       (let ((free-kv-slot (hash-table-next-free-kv hash-table)))
-         ;; Double-check for overflow.
-         (aver (not (zerop free-kv-slot)))
-         (setf (hash-table-next-free-kv hash-table)
-               (aref next-vector free-kv-slot))
-         (incf (hash-table-number-entries hash-table))
-
-         (setf (aref kv-vector (* 2 free-kv-slot)) key)
-         (setf (aref kv-vector (1+ (* 2 free-kv-slot))) value)
-
-         ;; Setup the hash-vector if necessary.
-         (when hash-vector
-           (if (not eq-based)
-               (setf (aref hash-vector free-kv-slot) hashing)
-               (aver (= (aref hash-vector free-kv-slot) +magic-hash-vector-value+))))
-
-         ;; Push this slot into the next chain.
-         (setf (aref next-vector free-kv-slot) next)
-         (setf (aref index-vector index) free-kv-slot)))))
+   (let ((cache (hash-table-cache hash-table))
+         (kv-vector (hash-table-table hash-table)))
+
+     ;; Check the cache
+     (if (and cache (< cache (length kv-vector)) (eq (aref kv-vector cache) key))
+         ;; If cached, just store here
+         (setf (aref kv-vector (1+ cache)) value)
+
+       ;; Search for key in the hash table.
+       (multiple-value-bind (hashing eq-based)
+           (funcall (hash-table-hash-fun hash-table) key)
+         (declare (type hash hashing))
+         (let* ((index-vector (hash-table-index-vector hash-table))
+                (length (length index-vector))
+                (index (rem hashing length))
+                (next (aref index-vector index))
+                (kv-vector (hash-table-table hash-table))
+                (next-vector (hash-table-next-vector hash-table))
+                (hash-vector (hash-table-hash-vector hash-table))
+                (test-fun (hash-table-test-fun hash-table)))
+           (declare (type index index))
+           
+           (cond ((or eq-based (not hash-vector))
+                  (when eq-based
+                    (set-header-data kv-vector sb!vm:vector-valid-hashing-subtype))
+                  
+                  ;; Search next-vector chain for a matching key.
+                  (do ((next next (aref next-vector next)))
+                      ((zerop next))
+                    (declare (type index next))
+                    (when (eq key (aref kv-vector (* 2 next)))
+                      ;; Found, just replace the value.
+                      (setf (hash-table-cache hash-table) (* 2 next))
+                      (setf (aref kv-vector (1+ (* 2 next))) value)
+                      (return-from %puthash value))))
+                 (t
+                  ;; Search next-vector chain for a matching key.
+                  (do ((next next (aref next-vector next)))
+                      ((zerop next))
+                    (declare (type index next))
+                    (when (and (= hashing (aref hash-vector next))
+                               (funcall test-fun key
+                                        (aref kv-vector (* 2 next))))
+                      ;; Found, just replace the value.
+                      (setf (hash-table-cache hash-table) (* 2 next))
+                      (setf (aref kv-vector (1+ (* 2 next))) value)
+                      (return-from %puthash value)))))
+           
+           ;; Pop a KV slot off the free list
+           (let ((free-kv-slot (hash-table-next-free-kv hash-table)))
+             ;; Double-check for overflow.
+             (aver (not (zerop free-kv-slot)))
+             (setf (hash-table-next-free-kv hash-table)
+                   (aref next-vector free-kv-slot))
+             (incf (hash-table-number-entries hash-table))
+             
+             (setf (hash-table-cache hash-table) (* 2 free-kv-slot))
+             (setf (aref kv-vector (* 2 free-kv-slot)) key)
+             (setf (aref kv-vector (1+ (* 2 free-kv-slot))) value)
+             
+             ;; Setup the hash-vector if necessary.
+             (when hash-vector
+               (if (not eq-based)
+                   (setf (aref hash-vector free-kv-slot) hashing)
+                 (aver (= (aref hash-vector free-kv-slot) +magic-hash-vector-value+))))
+             
+             ;; Push this slot into the next chain.
+             (setf (aref next-vector free-kv-slot) next)
+             (setf (aref index-vector index) free-kv-slot)))))))
   value)
 
 (defun remhash (key hash-table)
@@ -555,6 +575,9 @@
          ((not (zerop (hash-table-needing-rehash hash-table)))
           (flush-needing-rehash hash-table)))
 
+   ;; For now, just clear the cache   
+   (setf (hash-table-cache hash-table) nil)
+
    ;; Search for key in the hash table.
    (multiple-value-bind (hashing eq-based)
        (funcall (hash-table-hash-fun hash-table) key)
@@ -637,6 +660,7 @@
     ;; Clear the hash-vector.
     (when hash-vector
       (fill hash-vector +magic-hash-vector-value+)))
+  (setf (hash-table-cache hash-table) nil)
   (setf (hash-table-number-entries hash-table) 0)
   hash-table)
 \f

diff --git a/version.lisp-expr b/version.lisp-expr
index db875ec..430b781 100644 (file)
--- a/version.lisp-expr
+++ b/version.lisp-expr
@@ -17,4 +17,4 @@
 ;;; checkins which aren't released. (And occasionally for internal
 ;;; versions, especially for internal versions off the main CVS
 ;;; branch, it gets hairier, e.g. "0.pre7.14.flaky4.13".)
-"0.9.3.29"
+"0.9.3.30"