(in-package "SB!IMPL")
+;;; Like CMU CL, we use HEAPSORT. However, other than that, this code
+;;; isn't really related to the CMU CL code, since instead of trying
+;;; to generalize the CMU CL code to allow START and END values, this
+;;; code has been written from scratch following Chapter 7 of
+;;; _Introduction to Algorithms_ by Corman, Rivest, and Shamir.
+(defun sort-vector (vector start end predicate key)
+ (sort-vector vector start end predicate key))
+
+;;; This is MAYBE-INLINE because it's not too hard to have an
+;;; application where sorting is a major bottleneck, and inlining it
+;;; allows the compiler to make enough optimizations that it might be
+;;; worth the (large) cost in space.
+(declaim (maybe-inline sort))
(defun sort (sequence predicate &key key)
#!+sb-doc
- "Destructively sorts sequence. Predicate should return non-Nil if
- Arg1 is to precede Arg2."
- (typecase sequence
- (simple-vector
- (if (> (the fixnum (length (the simple-vector sequence))) 0)
- (sort-simple-vector sequence predicate key)
- sequence))
- (list
- (sort-list sequence predicate key))
- (vector
- (if (> (the fixnum (length sequence)) 0)
- (sort-vector sequence predicate key)
- sequence))
- (t
- (error 'simple-type-error
- :datum sequence
- :expected-type 'sequence
- :format-control "~S is not a sequence."
- :format-arguments (list sequence)))))
-\f
-;;;; sorting vectors
-
-;;; Make simple-vector and miscellaneous vector sorting functions.
-(macrolet (;; BUILD-HEAP rearranges seq elements into a heap to start heap
- ;; sorting.
- (build-heap (seq type len-1 pred key)
- (let ((i (gensym)))
- `(do ((,i (floor ,len-1 2) (1- ,i)))
- ((minusp ,i) ,seq)
- (declare (fixnum ,i))
- (heapify ,seq ,type ,i ,len-1 ,pred ,key))))
- ;; HEAPIFY, assuming both sons of root are heaps, percolates the
- ;; root element through the sons to form a heap at root. Root and
- ;; max are zero based coordinates, but the heap algorithm only works
- ;; on arrays indexed from 1 through N (not 0 through N-1); This is
- ;; because a root at I has sons at 2*I and 2*I+1 which does not work
- ;; for a root at 0. Because of this, boundaries, roots, and
- ;; termination are computed using 1..N indexes.
- (heapify (seq vector-ref root max pred key)
- (let ((heap-root (gensym))
- (heap-max (gensym))
- (root-ele (gensym))
- (root-key (gensym))
- (heap-max/2 (gensym))
- (heap-l-son (gensym))
- (one-son (gensym))
- (one-son-ele (gensym))
- (one-son-key (gensym))
- (r-son-ele (gensym))
- (r-son-key (gensym))
- (var-root (gensym)))
- `(let* ((,var-root ,root) ; (necessary to not clobber calling
- ; root var)
- (,heap-root (1+ ,root))
- (,heap-max (1+ ,max))
- (,root-ele (,vector-ref ,seq ,root))
- (,root-key (apply-key ,key ,root-ele))
- (,heap-max/2 (ash ,heap-max -1))) ; (floor heap-max 2)
- (declare (fixnum ,var-root ,heap-root ,heap-max ,heap-max/2))
- (loop
- (if (> ,heap-root ,heap-max/2) (return))
- (let* ((,heap-l-son (ash ,heap-root 1)) ; (* 2 heap-root)
- ;; l-son index in seq (0..N-1) is one less than heap
- ;; computation.
- (,one-son (1- ,heap-l-son))
- (,one-son-ele (,vector-ref ,seq ,one-son))
- (,one-son-key (apply-key ,key ,one-son-ele)))
- (declare (fixnum ,heap-l-son ,one-son))
- (if (< ,heap-l-son ,heap-max)
- ;; There is a right son.
- (let* ((,r-son-ele (,vector-ref ,seq ,heap-l-son))
- (,r-son-key (apply-key ,key ,r-son-ele)))
- ;; Choose the greater of the two sons.
- (when (funcall ,pred ,one-son-key ,r-son-key)
- (setf ,one-son ,heap-l-son)
- (setf ,one-son-ele ,r-son-ele)
- (setf ,one-son-key ,r-son-key))))
- ;; If greater son is less than root, then we've formed a
- ;; heap again..
- (if (funcall ,pred ,one-son-key ,root-key) (return))
- ;; ..else put greater son at root and make greater son
- ;; node be the root.
- (setf (,vector-ref ,seq ,var-root) ,one-son-ele)
- (setf ,heap-root (1+ ,one-son)) ; (one plus to be in heap coordinates)
- (setf ,var-root ,one-son))) ; actual index into vector for root ele
- ;; Now really put percolated value into heap at the
- ;; appropriate root node.
- (setf (,vector-ref ,seq ,var-root) ,root-ele))))
- (def-vector-sort-fun (fun-name vector-ref)
- `(defun ,fun-name (seq pred key)
- (let ((len-1 (1- (length (the vector seq)))))
- (declare (fixnum len-1))
- (build-heap seq ,vector-ref len-1 pred key)
- (do* ((i len-1 i-1)
- (i-1 (1- i) (1- i-1)))
- ((zerop i) seq)
- (declare (fixnum i i-1))
- (rotatef (,vector-ref seq 0) (,vector-ref seq i))
- (heapify seq ,vector-ref 0 i-1 pred key))))))
- (def-vector-sort-fun sort-vector aref)
- (def-vector-sort-fun sort-simple-vector svref))
+ "Destructively sort SEQUENCE. PREDICATE should return non-NIL if
+ ARG1 is to precede ARG2."
+ (let ((predicate-function (%coerce-callable-to-fun predicate))
+ (key-function (and key (%coerce-callable-to-fun key))))
+ (typecase sequence
+ (list (stable-sort-list sequence predicate-function key-function))
+ (vector
+ (with-array-data ((vector (the vector sequence))
+ (start 0)
+ (end (length sequence)))
+ (sort-vector vector start end predicate-function key-function))
+ sequence)
+ (t
+ (error 'simple-type-error
+ :datum sequence
+ :expected-type 'sequence
+ :format-control "~S is not a sequence."
+ :format-arguments (list sequence))))))
\f
;;;; stable sorting
(defun stable-sort (sequence predicate &key key)
#!+sb-doc
- "Destructively sorts sequence. Predicate should return non-Nil if
- Arg1 is to precede Arg2."
+ "Destructively sort SEQUENCE. PREDICATE should return non-NIL if
+ ARG1 is to precede ARG2."
(typecase sequence
(simple-vector
(stable-sort-simple-vector sequence predicate key))
(list
- (sort-list sequence predicate key))
+ (stable-sort-list sequence predicate key))
(vector
(stable-sort-vector sequence predicate key))
(t
:expected-type 'sequence
:format-control "~S is not a sequence."
:format-arguments (list sequence)))))
+\f
+;;; APPLY-KEYED-PRED saves us a function call sometimes.
+(eval-when (:compile-toplevel :execute)
+ (sb!xc:defmacro apply-keyed-pred (one two pred key)
+ `(if ,key
+ (funcall ,pred (funcall ,key ,one)
+ (funcall ,key ,two))
+ (funcall ,pred ,one ,two)))
+) ; EVAL-WHEN
+\f
+;;;; stable sort of lists
-;;; stable sort of lists
+(defun last-cons-of (list)
+ (loop (let ((rest (rest list)))
+ (if rest
+ (setf list rest)
+ (return list)))))
-;;; SORT-LIST uses a bottom up merge sort. First a pass is made over the list
-;;; grabbing one element at a time and merging it with the next one form pairs
-;;; of sorted elements. Then n is doubled, and elements are taken in runs of
-;;; two, merging one run with the next to form quadruples of sorted elements.
-;;; This continues until n is large enough that the inner loop only runs for
-;;; one iteration; that is, there are only two runs that can be merged, the
-;;; first run starting at the beginning of the list, and the second being the
-;;; remaining elements.
+;;; Destructively merge LIST-1 with LIST-2 (given that they're already
+;;; sorted w.r.t. PRED-FUN on KEY-FUN, giving output sorted the same
+;;; way). In the resulting list, elements of LIST-1 are guaranteed to
+;;; come before equal elements of LIST-2.
+;;;
+;;; Return (VALUES HEAD TAILTAIL), where HEAD is the same value you'd
+;;; expect from MERGE, and TAILTAIL is the last cons in the list (i.e.
+;;; the last cons in the list which NRECONC calls TAIL).
+(defun merge-lists* (list-1 list-2 pred-fun key-fun)
+ (declare (type list list-1 list-2))
+ (declare (type function pred-fun key-fun))
+ (cond ((null list-1) (values list-2 (last-cons-of list-2)))
+ ((null list-2) (values list-1 (last-cons-of list-1)))
+ (t (let* ((reversed-result-so-far nil)
+ (key-1 (funcall key-fun (car list-1)))
+ (key-2 (funcall key-fun (car list-2))))
+ (loop
+ (macrolet ((frob (list-i key-i other-list)
+ `(progn
+ ;; basically
+ ;; (PUSH (POP ,LIST-I) REVERSED-RESULT-SO-FAR),
+ ;; except doing some fancy footwork to
+ ;; reuse the cons cell:
+ (psetf (cdr ,list-i) reversed-result-so-far
+ reversed-result-so-far ,list-i
+ ,list-i (cdr ,list-i))
+ ;; Now maybe we're done.
+ (if (endp ,list-i)
+ (return (values (nreconc
+ reversed-result-so-far
+ ,other-list)
+ (last-cons-of
+ ,other-list)))
+ (setf ,key-i
+ (funcall key-fun (car ,list-i)))))))
+ ;; Note that by making KEY-2 the first arg to
+ ;; PRED-FUN, we arrange that if PRED-FUN is a function
+ ;; in the #'< style, the outcome is stably sorted.
+ (if (funcall pred-fun key-2 key-1)
+ (frob list-2 key-2 list-1)
+ (frob list-1 key-1 list-2))))))))
-(defun sort-list (list pred key)
+;;; STABLE-SORT-LIST uses a bottom-up merge sort. First a pass is made
+;;; over the list grabbing one element at a time and merging it with
+;;; the next one to form pairs of sorted elements. Then N is doubled,
+;;; and elements are taken in runs of two, merging one run with the
+;;; next to form quadruples of sorted elements. This continues until N
+;;; is large enough that the inner loop only runs for one iteration;
+;;; that is, there are only two runs that can be merged, the first run
+;;; starting at the beginning of the list, and the second being the
+;;; remaining elements.
+(defun stable-sort-list (list pred key)
(let ((head (cons :header list)) ; head holds on to everything
- (n 1) ; bottom-up size of lists to be merged
+ (n 1) ; bottom-up size of lists to be merged
unsorted ; unsorted is the remaining list to be
; broken into n size lists and merged
list-1 ; list-1 is one length n list to be merged
- last) ; last points to the last visited cell
+ last ; last points to the last visited cell
+ (pred-fun (%coerce-callable-to-fun pred))
+ (key-fun (if key
+ (%coerce-callable-to-fun key)
+ #'identity)))
(declare (fixnum n))
(loop
- ;; start collecting runs of n at the first element
+ ;; Start collecting runs of N at the first element.
(setf unsorted (cdr head))
- ;; tack on the first merge of two n-runs to the head holder
+ ;; Tack on the first merge of two N-runs to the head holder.
(setf last head)
(let ((n-1 (1- n)))
(declare (fixnum n-1))
(let ((temp (nthcdr n-1 list-1))
list-2)
(cond (temp
- ;; there are enough elements for a second run
+ ;; There are enough elements for a second run.
(setf list-2 (cdr temp))
(setf (cdr temp) nil)
(setf temp (nthcdr n-1 list-2))
(cond (temp
(setf unsorted (cdr temp))
(setf (cdr temp) nil))
- ;; the second run goes off the end of the list
+ ;; The second run goes off the end of the list.
(t (setf unsorted nil)))
(multiple-value-bind (merged-head merged-last)
- (merge-lists* list-1 list-2 pred key)
- (setf (cdr last) merged-head)
- (setf last merged-last))
+ (merge-lists* list-1 list-2 pred-fun key-fun)
+ (setf (cdr last) merged-head
+ last merged-last))
(if (null unsorted) (return)))
- ;; if there is only one run, then tack it on to the end
+ ;; If there is only one run, then tack it on to the end.
(t (setf (cdr last) list-1)
(return)))))
(setf n (ash n 1)) ; (+ n n)
- ;; If the inner loop only executed once, then there were only enough
- ;; elements for two runs given n, so all the elements have been merged
- ;; into one list. This may waste one outer iteration to realize.
+ ;; If the inner loop only executed once, then there were only
+ ;; enough elements for two runs given n, so all the elements
+ ;; have been merged into one list. This may waste one outer
+ ;; iteration to realize.
(if (eq list-1 (cdr head))
(return list-1))))))
-
-;;; APPLY-PRED saves us a function call sometimes.
-(eval-when (:compile-toplevel :execute)
- (sb!xc:defmacro apply-pred (one two pred key)
- `(if ,key
- (funcall ,pred (funcall ,key ,one)
- (funcall ,key ,two))
- (funcall ,pred ,one ,two)))
-) ; EVAL-WHEN
-
-(defvar *merge-lists-header* (list :header))
-
-;;; MERGE-LISTS* originally written by Jim Large.
-;;; modified to return a pointer to the end of the result
-;;; and to not cons header each time its called.
-;;; It destructively merges list-1 with list-2. In the resulting
-;;; list, elements of list-2 are guaranteed to come after equal elements
-;;; of list-1.
-(defun merge-lists* (list-1 list-2 pred key)
- (do* ((result *merge-lists-header*)
- (P result)) ; points to last cell of result
- ((or (null list-1) (null list-2)) ; done when either list used up
- (if (null list-1) ; in which case, append the
- (rplacd p list-2) ; other list
- (rplacd p list-1))
- (do ((drag p lead)
- (lead (cdr p) (cdr lead)))
- ((null lead)
- (values (prog1 (cdr result) ; Return the result sans header
- (rplacd result nil)) ; (free memory, be careful)
- drag)))) ; and return pointer to last element.
- (cond ((apply-pred (car list-2) (car list-1) pred key)
- (rplacd p list-2) ; Append the lesser list to last cell of
- (setq p (cdr p)) ; result. Note: test must bo done for
- (pop list-2)) ; LIST-2 < LIST-1 so merge will be
- (T (rplacd p list-1) ; stable for LIST-1.
- (setq p (cdr p))
- (pop list-1)))))
-
-;;; stable sort of vectors
+\f
+;;;; stable sort of vectors
;;; Stable sorting vectors is done with the same algorithm used for
;;; lists, using a temporary vector to merge back and forth between it
(incf ,target-i)
(incf ,i))
(return))
- ((apply-pred (,source-ref ,source ,j)
- (,source-ref ,source ,i)
- ,pred ,key)
+ ((apply-keyed-pred (,source-ref ,source ,j)
+ (,source-ref ,source ,i)
+ ,pred ,key)
(setf (,target-ref ,target ,target-i)
(,source-ref ,source ,j))
(incf ,j))
(incf ,i)))
(incf ,target-i)))))
-;;; VECTOR-MERGE-SORT is the same algorithm used to stable sort lists, but
-;;; it uses a temporary vector. Direction determines whether we are merging
-;;; into the temporary (T) or back into the given vector (NIL).
-
+;;; VECTOR-MERGE-SORT is the same algorithm used to stable sort lists,
+;;; but it uses a temporary vector. DIRECTION determines whether we
+;;; are merging into the temporary (T) or back into the given vector
+;;; (NIL).
(sb!xc:defmacro vector-merge-sort (vector pred key vector-ref)
(let ((vector-len (gensym)) (n (gensym))
(direction (gensym)) (unsorted (gensym))
) ; EVAL-when
-;;; Temporary vector for stable sorting vectors.
+;;; temporary vector for stable sorting vectors
(defvar *merge-sort-temp-vector*
(make-array 50))
(defun stable-sort-vector (vector pred key)
(vector-merge-sort vector pred key aref))
-
+\f
;;;; merging
(eval-when (:compile-toplevel :execute)
;;; MERGE-VECTORS returns a new vector which contains an interleaving
-;;; of the elements of vector-1 and vector-2. Elements from vector-2 are
-;;; chosen only if they are strictly less than elements of vector-1,
-;;; (pred elt-2 elt-1), as specified in the manual.
-
+;;; of the elements of VECTOR-1 and VECTOR-2. Elements from VECTOR-2
+;;; are chosen only if they are strictly less than elements of
+;;; VECTOR-1, (PRED ELT-2 ELT-1), as specified in the manual.
(sb!xc:defmacro merge-vectors (vector-1 length-1 vector-2 length-2
result-vector pred key access)
(let ((result-i (gensym))
(incf ,result-i)
(incf ,i))
(return ,result-vector))
- ((apply-pred (,access ,vector-2 ,j) (,access ,vector-1 ,i)
- ,pred ,key)
+ ((apply-keyed-pred (,access ,vector-2 ,j) (,access ,vector-1 ,i)
+ ,pred ,key)
(setf (,access ,result-vector ,result-i)
(,access ,vector-2 ,j))
(incf ,j))
(defun merge (result-type sequence1 sequence2 predicate &key key)
#!+sb-doc
- "The sequences Sequence1 and Sequence2 are destructively merged into
- a sequence of type Result-Type using the Predicate to order the elements."
- (if (eq result-type 'list)
- (let ((result (merge-lists* (coerce sequence1 'list)
- (coerce sequence2 'list)
- predicate key)))
- result)
- (let* ((vector-1 (coerce sequence1 'vector))
- (vector-2 (coerce sequence2 'vector))
- (length-1 (length vector-1))
- (length-2 (length vector-2))
- (result (make-sequence-of-type result-type (+ length-1 length-2))))
- (declare (vector vector-1 vector-2)
- (fixnum length-1 length-2))
-
- #!+high-security
- (check-type-var result result-type)
- (if (and (simple-vector-p result)
- (simple-vector-p vector-1)
- (simple-vector-p vector-2))
- (merge-vectors vector-1 length-1 vector-2 length-2
- result predicate key svref)
- (merge-vectors vector-1 length-1 vector-2 length-2
- result predicate key aref)))))
+ "Merge the sequences SEQUENCE1 and SEQUENCE2 destructively into a
+ sequence of type RESULT-TYPE using PREDICATE to order the elements."
+ ;; FIXME: This implementation is remarkably inefficient in various
+ ;; ways. In decreasing order of estimated user astonishment, I note:
+ ;; full calls to SPECIFIER-TYPE at runtime; copying input vectors
+ ;; to lists before doing MERGE-LISTS*; and walking input lists
+ ;; (because of the call to MERGE-LISTS*, which walks the list to
+ ;; find the last element for its second return value) even in cases
+ ;; like (MERGE 'LIST (LIST 1) (LIST 2 3 4 5 ... 1000)) where one list
+ ;; can be largely ignored. -- WHN 2003-01-05
+ (let ((type (specifier-type result-type)))
+ (cond
+ ((csubtypep type (specifier-type 'list))
+ ;; the VECTOR clause, below, goes through MAKE-SEQUENCE, so
+ ;; benefits from the error checking there. Short of
+ ;; reimplementing everything, we can't do the same for the LIST
+ ;; case, so do relevant length checking here:
+ (let ((s1 (coerce sequence1 'list))
+ (s2 (coerce sequence2 'list))
+ (pred-fun (%coerce-callable-to-fun predicate))
+ (key-fun (if key
+ (%coerce-callable-to-fun key)
+ #'identity)))
+ (when (type= type (specifier-type 'list))
+ (return-from merge (values (merge-lists* s1 s2 pred-fun key-fun))))
+ (when (eq type *empty-type*)
+ (bad-sequence-type-error nil))
+ (when (type= type (specifier-type 'null))
+ (if (and (null s1) (null s2))
+ (return-from merge 'nil)
+ ;; FIXME: This will break on circular lists (as,
+ ;; indeed, will the whole MERGE function).
+ (sequence-type-length-mismatch-error type
+ (+ (length s1)
+ (length s2)))))
+ (if (csubtypep (specifier-type '(cons nil t)) type)
+ (if (and (null s1) (null s2))
+ (sequence-type-length-mismatch-error type 0)
+ (values (merge-lists* s1 s2 pred-fun key-fun)))
+ (sequence-type-too-hairy result-type))))
+ ((csubtypep type (specifier-type 'vector))
+ (let* ((vector-1 (coerce sequence1 'vector))
+ (vector-2 (coerce sequence2 'vector))
+ (length-1 (length vector-1))
+ (length-2 (length vector-2))
+ (result (make-sequence result-type
+ (+ length-1 length-2))))
+ (declare (vector vector-1 vector-2)
+ (fixnum length-1 length-2))
+ (if (and (simple-vector-p result)
+ (simple-vector-p vector-1)
+ (simple-vector-p vector-2))
+ (merge-vectors vector-1 length-1 vector-2 length-2
+ result predicate key svref)
+ (merge-vectors vector-1 length-1 vector-2 length-2
+ result predicate key aref))))
+ (t (bad-sequence-type-error result-type)))))
projects / sbcl.git / blobdiff