Re: Division inconsistency between interpreted and compiled Lush

This is a bit late...

On 12/24/05, Yann LeCun <[email protected]> wrote:
> Well, I'm not sure how to fix this either, short of extending the
> interpreter to handle different numerical types, which is a
> non-trivial job (right now, everything is a double in interpreted
> mode).
>
> Casting args of / into double would only be a partial solution.  The
> same other operation also have different behaviors for different
> numerical types. One potential (but rather annoying) solution is to
> have numerical functions cast their arguments to a single type (double
> for most ops) and return a single type, and make the compiler complain
> when the result is assigned to a different type without explicit
> conversion.
>
> > What's the file that translates arithmetic functions into C operations? Is
> > it dz.c?
>
> Most of it is in lsh/compiler/dh-macro.lsh
> Look for "dhm-c /"
>
>   -- Yann
>
>
> > Hi, I'm not sure where to fix this, but I think the compiler should cast
> > any integer arguments to the / function into floats. Right now, both unary
> > and binary division work differently in interpreted code and in compiled
> > code.
> >
> > What's the file that translates arithmetic functions into C operations? Is
> > it dz.c?
> >
> > Yury

It seems to me that the division functions "/", "2/" suffer the most
from this. What other functions return different values if used with
integers?

The patch below fixes this. Is it okay to commit it?

Yury

Index: lsh/compiler/dh-macro.lsh
===================================================================
RCS file: /cvsroot/lush/lush/lsh/compiler/dh-macro.lsh,v
retrieving revision 1.47
diff -u -r1.47 dh-macro.lsh
--- lsh/compiler/dh-macro.lsh   7 Sep 2005 18:05:30 -0000       1.47
+++ lsh/compiler/dh-macro.lsh   11 Jan 2006 06:17:41 -0000
@@ -1123,7 +1123,11 @@
 (dhm-t /(source)
   (when (and (<> 2 (length source)) (<> 3 (length source)) )
        (dhc-error "wrong number of arguments"))
-  (process-numerical-args-t (cdr source)))
+  (let ((tnode (process-numerical-args-t (cdr source))))
+    ;; integer division in C isn't used
+    (when (==> :tnode:type is-an-int)
+      (setq :tnode:type (new dhc-type 'dht-real)))
+    tnode))

 (de dhc-c-cast (type)
     (if (==> type is-a-real) "(real)"
@@ -1133,10 +1137,10 @@
        (let ((arg1 (dhc-parse-expr-c (cadr source)
                                     (cadr :treetype:tn-list) ())))
         (if (= (length source) 2)
-            (sprintf "(1/%s%s)" (dhc-c-cast :(cadr :treetype:tn-list):type)
+            (sprintf "(1/%s%s)" (dhc-c-cast :treetype:type)
                      arg1)
           (sprintf "(%s/%s%s)"
-                   arg1 (dhc-c-cast :(cadr :treetype:tn-list):type)
+                   arg1 (dhc-c-cast :treetype:type)
                    (dhc-parse-expr-c (caddr source)
                                      (caddr :treetype:tn-list)
                                      ())))))
@@ -1281,7 +1285,7 @@
 (generate-monadic '1+ "((%s)+1)" "((%s)+1)" "((%s)+1)")
 (generate-monadic '1- "((%s)-1)" "((%s)-1)" "((%s)-1)")
 (generate-monadic '2* "((%s)*2)" "((%s)*2)" "((%s)*2)")
-(generate-monadic '2/ "((%s)/2)" "((%s)/2)" "((%s)/2)")
+(generate-monadic '2/ "((%s)/2.0)" "((%s)/2.0f)" ())

 (dhm-t seed(source)
   (if (<> (length source) 2)


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