mpz_cmp_d and NaNs in = and <

mpz_cmp_d and NaNs in = and <

[Kevin Ryde]

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A concrete proposal for NaNs in = and <.  As mentioned previously,
mpz_cmp_d doesn't accept them.

        * numbers.c (scm_num_eq_p, scm_less_p): Don't pass NaN to mpz_cmp_d.

        * tests/numbers.test (=, <): Add tests involving NaNs.

Are the comments correct about SCM_COMPLEXP numbers never having a
zero imaginary part?  I suspect this means the mpz_cmp_d's in the
complex/bignum cases are not reached.  In fact perhaps any comparison
(= complex non-complex) would be #f without any testing.


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--- numbers.c.~1.181.~	2003-05-04 09:09:49.000000000 +1000
+++ numbers.c	2003-05-05 12:04:05.000000000 +1000
@@ -2520,12 +2520,15 @@
       scm_remember_upto_here_2 (x, y);
       return SCM_BOOL (0 == cmp);
     } else if (SCM_REALP (y)) {
-      int cmp = mpz_cmp_d (SCM_I_BIG_MPZ (x), SCM_REAL_VALUE (y));
+      int cmp;
+      if (xisnan (SCM_REAL_VALUE (y))) return SCM_BOOL_F;
+      cmp = mpz_cmp_d (SCM_I_BIG_MPZ (x), SCM_REAL_VALUE (y));
       scm_remember_upto_here_1 (x);
       return SCM_BOOL (0 == cmp);
     } else if (SCM_COMPLEXP (y)) {
       int cmp;
       if (0.0 != SCM_COMPLEX_IMAG (y)) return SCM_BOOL_F;
+      if (xisnan (SCM_COMPLEX_REAL (y))) return SCM_BOOL_F;
       cmp = mpz_cmp_d (SCM_I_BIG_MPZ (x), SCM_COMPLEX_REAL (y));
       scm_remember_upto_here_1 (x);
       return SCM_BOOL (0 == cmp);
@@ -2536,7 +2539,9 @@
     if (SCM_INUMP (y)) {
       return SCM_BOOL (SCM_REAL_VALUE (x) == (double) SCM_INUM (y));
     } else if (SCM_BIGP (y)) {
-      int cmp = mpz_cmp_d (SCM_I_BIG_MPZ (y), SCM_REAL_VALUE (x));
+      int cmp;
+      if (xisnan (SCM_REAL_VALUE (x))) return SCM_BOOL_F;
+      cmp = mpz_cmp_d (SCM_I_BIG_MPZ (y), SCM_REAL_VALUE (x));
       scm_remember_upto_here_1 (y);
       return SCM_BOOL (0 == cmp);
     } else if (SCM_REALP (y)) {
@@ -2554,6 +2559,7 @@
     } else if (SCM_BIGP (y)) {
       int cmp;
       if (0.0 != SCM_COMPLEX_IMAG (x)) return SCM_BOOL_F;
+      if (xisnan (SCM_COMPLEX_REAL (x))) return SCM_BOOL_F;
       cmp = mpz_cmp_d (SCM_I_BIG_MPZ (y), SCM_COMPLEX_REAL (x));
       scm_remember_upto_here_1 (y);
       return SCM_BOOL (0 == cmp);
@@ -2603,7 +2609,9 @@
       scm_remember_upto_here_2 (x, y);
       return SCM_BOOL (cmp < 0);
     } else if (SCM_REALP (y)) {
-      int cmp = mpz_cmp_d (SCM_I_BIG_MPZ (x), SCM_REAL_VALUE (y));
+      int cmp;
+      if (xisnan (SCM_REAL_VALUE (y))) return SCM_BOOL_F;
+      cmp = mpz_cmp_d (SCM_I_BIG_MPZ (x), SCM_REAL_VALUE (y));
       scm_remember_upto_here_1 (x);
       return SCM_BOOL (cmp < 0);
     } else {
@@ -2613,7 +2621,9 @@
     if (SCM_INUMP (y)) {
       return SCM_BOOL (SCM_REAL_VALUE (x) < (double) SCM_INUM (y));
     } else if (SCM_BIGP (y)) {
-      int cmp = mpz_cmp_d (SCM_I_BIG_MPZ (y), SCM_REAL_VALUE (x));
+      int cmp;
+      if (xisnan (SCM_REAL_VALUE (x))) return SCM_BOOL_F;
+      cmp = mpz_cmp_d (SCM_I_BIG_MPZ (y), SCM_REAL_VALUE (x));
       scm_remember_upto_here_1 (y);
       return SCM_BOOL (cmp > 0);
     } else if (SCM_REALP (y)) {

[-- Attachment #3: numbers.test.nan.diff --]
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Index: numbers.test
===================================================================
RCS file: /cvsroot/guile/guile/guile-core/test-suite/tests/numbers.test,v
retrieving revision 1.19
diff -u -u -r1.19 numbers.test
--- numbers.test	5 May 2003 23:04:02 -0000	1.19
+++ numbers.test	5 May 2003 23:22:53 -0000
@@ -1157,7 +1157,30 @@
   (expect-fail (= (+ 1 fixnum-max) fixnum-max))
   (expect-fail (= fixnum-min (- fixnum-min 1)))
   (expect-fail (= (- fixnum-min 1) fixnum-min))
-  (expect-fail (= (+ fixnum-max 1) (- fixnum-min 1))))
+  (expect-fail (= (+ fixnum-max 1) (- fixnum-min 1)))
+
+  (pass-if (not (= +nan.0 +nan.0)))
+  (pass-if (not (= 0 +nan.0)))
+  (pass-if (not (= +nan.0 0)))
+  (pass-if (not (= 1 +nan.0)))
+  (pass-if (not (= +nan.0 1)))
+  (pass-if (not (= -1 +nan.0)))
+  (pass-if (not (= +nan.0 -1)))
+
+  (pass-if (not (= (ash 1 256) +nan.0)))
+  (pass-if (not (= +nan.0 (ash 1 256))))
+  (pass-if (not (= (- (ash 1 256)) +nan.0)))
+  (pass-if (not (= +nan.0 (- (ash 1 256)))))
+
+  (pass-if (not (= (ash 1 8192) +nan.0)))
+  (pass-if (not (= +nan.0 (ash 1 8192))))
+  (pass-if (not (= (- (ash 1 8192)) +nan.0)))
+  (pass-if (not (= +nan.0 (- (ash 1 8192)))))
+
+  ;; in gmp prior to 4.2, mpz_cmp_d ended up treating NaN as 3*2^1023, make
+  ;; sure we've avoided that
+  (pass-if (not (= (ash 3 1023) +nan.0)))
+  (pass-if (not (= +nan.0 (ash 3 1023)))))
 
 ;;;
 ;;; <
@@ -1486,7 +1509,34 @@
       (< (- fixnum-min 1) fixnum-min))
 
     (pass-if "n = fixnum-min - 1"
-      (not (< (- fixnum-min 1) (- fixnum-min 1))))))
+      (not (< (- fixnum-min 1) (- fixnum-min 1)))))
+
+  (pass-if (not (< +nan.0 +nan.0)))
+  (pass-if (not (< 0 +nan.0)))
+  (pass-if (not (< +nan.0 0)))
+  (pass-if (not (< 1 +nan.0)))
+  (pass-if (not (< +nan.0 1)))
+  (pass-if (not (< -1 +nan.0)))
+  (pass-if (not (< +nan.0 -1)))
+
+  (pass-if (not (< (ash 1 256) +nan.0)))
+  (pass-if (not (< +nan.0 (ash 1 256))))
+  (pass-if (not (< (- (ash 1 256)) +nan.0)))
+  (pass-if (not (< +nan.0 (- (ash 1 256)))))
+  
+  (pass-if (not (< (ash 1 8192) +nan.0)))
+  (pass-if (not (< +nan.0 (ash 1 8192))))
+  (pass-if (not (< (- (ash 1 8192)) +nan.0)))
+  (pass-if (not (< +nan.0 (- (ash 1 8192)))))
+
+  ;; in gmp prior to 4.2, mpz_cmp_d ended up treating NaN as 3*2^1023, make
+  ;; sure we've avoided that
+  (pass-if (not (< (ash 3 1023) +nan.0)))
+  (pass-if (not (< (1+ (ash 3 1023)) +nan.0)))
+  (pass-if (not (< (1- (ash 3 1023)) +nan.0)))
+  (pass-if (not (< +nan.0 (ash 3 1023))))
+  (pass-if (not (< +nan.0 (1+ (ash 3 1023)))))
+  (pass-if (not (< +nan.0 (1- (ash 3 1023))))))
 
 ;;;
 ;;; >

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Re: mpz_cmp_d and NaNs in = and <

[Kevin Ryde]

I wrote:
>
>         * numbers.c (scm_num_eq_p, scm_less_p): Don't pass NaN to mpz_cmp_d.
>         * tests/numbers.test (=, <): Add tests involving NaNs.

I applied this change.  I left in the tests on complex numbers in `=';
someone smarter than me will have to advise whether it's true in fact
that they're not reached (on account of the imaginary part always
being non-zero).


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Re: mpz_cmp_d and NaNs in = and <

[Marius Vollmer]

Kevin Ryde <user42@zip.com.au> writes:

> I applied this change.  I left in the tests on complex numbers in `=';
> someone smarter than me will have to advise whether it's true in fact
> that they're not reached (on account of the imaginary part always
> being non-zero).

I think that a lot of places expect it to be true that all complex
number objects in Guile have a non-zero imaginary part.  But your
conservative approach is OK, nevertheless, and should probably remain
that way.  For example, we can't currently represent negative
imaginary zero.  we might want to change that, maybe.

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Re: mpz_cmp_d and NaNs in = and <

[Kevin Ryde]

Marius Vollmer <mvo@zagadka.de> writes:
>
> For example, we can't currently represent negative imaginary zero.

Ah yes, I guess the ==0 in scm_make_complex doesn't recognise the
distincation.

> we might want to change that, maybe.

Personally I'm not a fan of negative zero, it's pretty hard to see a
proper use for it.


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Re: mpz_cmp_d and NaNs in = and <

[rm]

On Tue, May 13, 2003 at 09:13:54AM +1000, Kevin Ryde wrote:
> Marius Vollmer <mvo@zagadka.de> writes:
> >
> > For example, we can't currently represent negative imaginary zero.
> 
> Ah yes, I guess the ==0 in scm_make_complex doesn't recognise the
> distincation.
> 
> > we might want to change that, maybe.
> 
> Personally I'm not a fan of negative zero, it's pretty hard to see a
> proper use for it.

Divide by it and you'll see  :-)

 Ralfd
> 
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Re: mpz_cmp_d and NaNs in = and <

[Kevin Ryde]

rm@fabula.de writes:
>
> Divide by it and you'll see  :-)

Oh, well, all I mean is that it's hard to see what it could represent.
A sort of remnant parity indicating how many positives and negatives
went into a product or something.  But I don't pretend to any great
expertise in this sort of area, so maybe it's good for something.


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Re: mpz_cmp_d and NaNs in = and <

[Marius Vollmer]

Kevin Ryde <user42@zip.com.au> writes:

> rm@fabula.de writes:
> >
> > Divide by it and you'll see  :-)
> 
> Oh, well, all I mean is that it's hard to see what it could represent.
> A sort of remnant parity indicating how many positives and negatives
> went into a product or something.  But I don't pretend to any great
> expertise in this sort of area, so maybe it's good for something.

There ought to be some good stuff in

       Branch Cuts for Complex Elementary Functions,
    or Much Ado About Nothing's Sign Bit

    in The State of the Art in Numerical Analysis,
       (eds. Iserles and Powell), Clarendon Press, Oxford, 1987.

but I couldn't find an online copy.

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