Faster mergesort conses less and no longer does slice fiddling

core/optimizer/known-words/known-words.factor

@@ -143,6 +143,14 @@ IN: optimizer.known-words
     { [ dup optimize-instance? ] [ optimize-instance ] }
 } define-optimizers
 
+! This is a special-case hack
+: redundant-array-capacity-check? ( #call -- ? )
+    dup in-d>> first node-literal [ 0 = ] [ fixnum? ] bi and ;
+
+\ array-capacity? {
+    { [ dup redundant-array-capacity-check? ] [ [ drop t ] f splice-quot ] }
+} define-optimizers
+
 ! eq? on the same object is always t
 { eq? = } {
     { { @ @ } [ 2drop t ] }

core/sorting/sorting-tests.factor

@@ -1,8 +1,8 @@
 USING: sorting sequences kernel math math.order random
-tools.test vectors ;
+tools.test vectors sets ;
 IN: sorting.tests
 
-[ [ ] ] [ [ ] natural-sort ] unit-test
+[ { } ] [ { } natural-sort ] unit-test
 
 [ { 270000000 270000001 } ]
 [ T{ slice f 270000000 270000002 270000002 } natural-sort ]
@@ -11,7 +11,9 @@ unit-test
 [ t ] [
     100 [
         drop
-        100 [ 20 random [ 1000 random ] replicate ] replicate natural-sort [ before=? ] monotonic?
+        100 [ 20 random [ 1000 random ] replicate ] replicate
+        dup natural-sort
+        [ set= ] [ nip [ before=? ] monotonic? ] 2bi and
     ] all?
 ] unit-test
 

core/sorting/sorting.factor

@@ -4,46 +4,127 @@ USING: accessors arrays kernel math sequences vectors math.order
 sequences sequences.private math.order ;
 IN: sorting
 
-DEFER: sort
+! Optimized merge-sort:
+!
+! 1) only allocates 2 temporary arrays
+
+! 2) first phase (interchanging pairs x[i], x[i+1] where
+! x[i] > x[i+1]) is handled specially
 
 <PRIVATE
 
-: <iterator> 0 tail-slice ; inline
+TUPLE: merge
+{ seq    array }
+{ accum  vector }
+{ accum1 vector }
+{ accum2 vector }
+{ from1  array-capacity }
+{ to1    array-capacity }
+{ from2  array-capacity }
+{ to2    array-capacity } ;
 
-: this ( slice -- obj )
+: dump ( from to seq accum -- )
-    dup slice-from swap slice-seq nth-unsafe ; inline
+    #! Optimize common case where to - from = 1.
+    >r >r 2dup swap - 1 =
+    [ drop r> nth-unsafe r> push ]
+    [ r> <slice> r> push-all ]
+    if ; inline
 
-: next ( iterator -- )
+: l-elt   [ from1>> ] [ seq>> ] bi nth-unsafe ; inline
-    dup slice-from 1+ swap set-slice-from ; inline
+: r-elt   [ from2>> ] [ seq>> ] bi nth-unsafe ; inline
+: l-done? [ from1>> ] [ to1>> ] bi number= ; inline
+: r-done? [ from2>> ] [ to2>> ] bi number= ; inline
+: dump-l  [ [ from1>> ] [ to1>> ] [ seq>> ] tri ] [ accum>> ] bi dump ; inline
+: dump-r  [ [ from2>> ] [ to2>> ] [ seq>> ] tri ] [ accum>> ] bi dump ; inline
+: l-next  [ [ l-elt ] [ [ 1+ ] change-from1 drop ] bi ] [ accum>> ] bi push ; inline
+: r-next  [ [ r-elt ] [ [ 1+ ] change-from2 drop ] bi ] [ accum>> ] bi push ; inline
+: decide  [ [ l-elt ] [ r-elt ] bi ] dip call +lt+ eq? ; inline
 
-: smallest ( iter1 iter2 quot -- elt )
+: (merge) ( merge quot -- )
-    >r over this over this r> call +lt+ eq?
+    over l-done? [ drop dump-r ] [
-    -rot ? [ this ] keep next ; inline
+        over r-done? [ drop dump-l ] [
-
+            2dup decide
-: (merge) ( iter1 iter2 quot accum -- )
+            [ over l-next ] [ over r-next ] if
-    >r pick empty? [
+            (merge)
-        drop nip r> push-all
-    ] [
-        over empty? [
-            2drop r> push-all
-        ] [
-            3dup smallest r> [ push ] keep (merge)
         ] if
     ] if ; inline
 
-: merge ( sorted1 sorted2 quot -- result )
+: flip-accum ( merge -- )
-    >r [ [ <iterator> ] bi@ ] 2keep r>
+    dup [ accum>> ] [ accum1>> ] bi eq? [
-    rot length rot length + <vector>
+        dup accum1>> underlying>> >>seq
-    [ (merge) ] [ underlying>> ] bi ; inline
+        dup accum2>> >>accum
+    ] [
+        dup accum1>> >>accum
+        dup accum2>> underlying>> >>seq
+    ] if
+    dup accum>> 0 >>length 2drop ; inline
 
-: conquer ( first second quot -- result )
+: <merge> ( seq -- merge )
-    [ tuck >r >r sort r> r> sort ] keep merge ; inline
+    \ merge new
+        over >vector >>accum1
+        swap length <vector> >>accum2
+        dup accum1>> underlying>> >>seq
+        dup accum2>> >>accum
+        dup accum>> 0 >>length drop ; inline
+
+: compute-midpoint ( merge -- merge )
+    dup [ from1>> ] [ to2>> ] bi + 2/ >>to1 ; inline
+
+: merging ( from to merge -- )
+    swap >>to2
+    swap >>from1
+    compute-midpoint
+    dup [ to1>> ] [ seq>> length ] bi min >>to1
+    dup [ to2>> ] [ seq>> length ] bi min >>to2
+    dup to1>> >>from2
+    drop ; inline
+
+: nth-chunk ( n size -- from to ) [ * dup ] keep + ; inline
+
+: chunks ( length size -- n ) [ align ] keep /i ; inline
+
+: each-chunk ( length size quot -- )
+    [ [ chunks ] keep ] dip
+    [ nth-chunk ] prepose curry
+    each-integer ; inline
+
+: merge ( from to merge quot -- )
+    [ [ merging ] keep ] dip (merge) ; inline
+
+: sort-pass ( merge size quot -- )
+    [
+        over flip-accum
+        over [ seq>> length ] 2dip
+    ] dip
+    [ merge ] 2curry each-chunk ; inline
+
+: sort-loop ( merge quot -- )
+    2 swap
+    [ pick seq>> length pick > ]
+    [ [ dup ] [ 1 shift ] [ ] tri* [ sort-pass ] 2keep ]
+    [ ] while 3drop ; inline
+
+: each-pair ( seq quot -- )
+    [ [ length 1+ 2/ ] keep ] dip
+    [ [ 1 shift dup 1+ ] dip ] prepose curry each-integer ; inline
+
+: (sort-pairs) ( i1 i2 seq quot accum -- )
+    >r >r 2dup length = [
+        nip nth r> drop r> push
+    ] [
+        tuck [ nth-unsafe ] 2bi@ 2dup r> call +gt+ eq?
+        [ swap ] when r> tuck [ push ] 2bi@
+    ] if ; inline
+
+: sort-pairs ( merge quot -- )
+    [ [ seq>> ] [ accum>> ] bi ] dip swap
+    [ (sort-pairs) ] 2curry each-pair ; inline
 
 PRIVATE>
 
-: sort ( seq quot -- sortedseq )
+: sort ( seq quot -- seq' )
-    over length 1 <=
+    [ <merge> ] dip
-    [ drop ] [ over >r >r halves r> conquer r> like ] if ;
+    [ sort-pairs ] [ sort-loop ] [ drop accum>> underlying>> ] 2tri ;
     inline
 
 : natural-sort ( seq -- sortedseq ) [ <=> ] sort ;