Hi,
The next release will add a more accurate Math.hypot implementation when
there are 3 or more arguments.
Best regards,
Fabrice.
On 2/25/20 1:10 AM, Diego Nehab wrote:
I think we both understand that there was a bug in the implementation. I simply meant to alert the list to the fact that, even with the fix, the implementation does not do what hypot is supposed to do (although it is much closer!)
On Mon, Feb 24, 2020 at 8:54 PM ian <ian@xxxxxxxxx <mailto:ian@xxxxxxxxx>> wrote:
Hi...
Please you both, read carefully.
The point was not to return the square root or not....
It was about correcting sum(a) to sum(a*a) ....
- r += a;
+ r += a*a;
E.g. : for js_mat_hypot (a,b) => sqrt(a²+b²) instead of sqrt(a+b) ....
Regards,
ian
Le 24/02/2020 à 20:50, Diego Nehab a écrit :
I think the sole motivation behind the existence of a library-- -- ian@xxxxxxxxx <mailto:ian@xxxxxxxxx>
function hypot is exactly that "Note". The bullets come almost for
free in the naive implementation.
On Mon, Feb 24, 2020 at 4:14 PM Wes Garland <wes@kingsds.network>
<mailto:wes@kingsds.network> wrote:
The current ES spec leaves this as "implementation-defined"
and does not discuss ULP at all -- except to recommend (but
not require) that the implementation back the routines in Math
with fdlibm.
That said, I believe this implementation is deficient in terms
of the spec (based on 30 seconds of code review, not deep
thought), at least for the cases where the arguments are +0 or
-0. It also violates the "care should be taken...." note, but
I see that as less critical.
|Math.hypot| returns an implementation-dependent approximation
of the square root of the sum of squares of its arguments.
* If no arguments are passed, the result is +0.
* If any argument is +∞, the result is +∞.
* If any argument is -∞, the result is +∞.
* If no argument is +∞ or -∞, and any argument is NaN, the
result is NaN.
* If all arguments are either +0 or -0, the result is +0.
Note
Implementations should take care to avoid the loss of
precision from overflows and underflows that are prone to
occur in naive implementations when this function is called
with two or more arguments.
Wes
On Sat, Feb 22, 2020 at 4:14 PM Diego Nehab
<diego.nehab@xxxxxxxxx <mailto:diego.nehab@xxxxxxxxx>> wrote:
I don’t know about the details of the JS hypot function,
but in C and C++ it usually guarantees the precision of
less than 1ulp. It’s not simply a convenience function to
save typing. This involves, for example, finding the
element of greatest absolute value and factoring it out of
the square root.
https://en.m.wikipedia.org/wiki/Hypot
On Sat, Feb 22, 2020 at 15:29 Yunkang YU
<yushroom@xxxxxxxxx <mailto:yushroom@xxxxxxxxx>> wrote:
Math.hypot() should return the square root of the sum
of *squares* of its arguments
--- a/quickjs.c
+++ b/quickjs.c
@@ -39923,7 +39923,7 @@ static JSValue
js_math_hypot(JSContext *ctx, JSValueConst this_val,
for(i = 0; i < argc; i++) {
if (JS_ToFloat64(ctx, &a, argv[i]))
return JS_EXCEPTION;
- r += a;
+ r += a*a;
}
r = sqrt(r);
}
-- Sent from my phone
-- Wesley W. Garland
CTO, Kings Distributed Systems
+1 613 539 6952
-- Développeur compulsif
