math: adding a fast-gcd that speeds up all ratio operations by up to 10 times for bignum ratios.

basis/math/functions/functions.factor

@@ -111,8 +111,20 @@ PRIVATE>
 : gcd ( x y -- a d )
     [ 0 1 ] 2dip (gcd) dup 0 < [ neg ] when ; inline
 
+MATH: fast-gcd ( x y -- d ) foldable
+
+<PRIVATE
+
+: simple-gcd ( x y -- d ) gcd nip ; inline
+
+PRIVATE>
+
+M: real fast-gcd simple-gcd ; inline
+
+M: bignum fast-gcd bignum-gcd ; inline
+
 : lcm ( a b -- c )
-    [ * ] 2keep gcd nip /i ; foldable
+    [ * ] 2keep fast-gcd /i ; foldable
 
 : divisor? ( m n -- ? )
     mod 0 = ; inline

basis/math/partial-dispatch/partial-dispatch.factor

@@ -1,9 +1,10 @@
 ! Copyright (C) 2008 Slava Pestov.
 ! See http://factorcode.org/license.txt for BSD license.
-USING: accessors kernel kernel.private math math.private words
-sequences parser namespaces make assocs quotations arrays
-generic generic.math hashtables effects compiler.units
-classes.algebra fry combinators ;
+USING: accessors kernel kernel.private math math.private
+math.functions math.functions.private sequences parser
+namespaces make assocs quotations arrays generic generic.math
+hashtables effects compiler.units classes.algebra fry
+combinators words ;
 IN: math.partial-dispatch
 
 PREDICATE: math-partial < word
@@ -215,6 +216,8 @@ SYMBOL: fast-math-ops
         \ mod \ fixnum-mod \ bignum-mod define-integer-ops
         \ /i \ fixnum/i \ bignum/i define-integer-ops
 
+        \ fast-gcd \ simple-gcd \ bignum-gcd define-integer-ops
+
         \ bitand \ fixnum-bitand \ bignum-bitand define-integer-ops
         \ bitor \ fixnum-bitor \ bignum-bitor define-integer-ops
         \ bitxor \ fixnum-bitxor \ bignum-bitxor define-integer-ops

basis/math/ratios/ratios.factor

@@ -30,7 +30,7 @@ M: integer /
         division-by-zero
     ] [
         dup 0 < [ [ neg ] bi@ ] when
-        2dup gcd nip [ /i ] curry bi@ fraction>
+        2dup fast-gcd [ /i ] curry bi@ fraction>
     ] if-zero ;
 
 M: ratio hashcode*