[Issue 3520] std.numeric.CustomFloat horribly broken
https://issues.dlang.org/show_bug.cgi?id=3520 Andrei Alexandrescu and...@erdani.com changed: What|Removed |Added Version|2.036 |D2 --
[Issue 3520] std.numeric.CustomFloat horribly broken
http://d.puremagic.com/issues/show_bug.cgi?id=3520 Brad Roberts bra...@puremagic.com changed: What|Removed |Added Status|ASSIGNED|RESOLVED CC||bra...@puremagic.com Resolution||FIXED --- Comment #6 from Brad Roberts bra...@puremagic.com 2010-06-15 02:08:50 PDT --- fixed in 2.047 -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email --- You are receiving this mail because: ---
[Issue 3520] std.numeric.CustomFloat horribly broken
http://d.puremagic.com/issues/show_bug.cgi?id=3520 --- Comment #5 from Rob Jacques sandf...@jhu.edu 2010-05-08 10:20:39 PDT --- Another issue: float.infinity isn't converted properly. -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email --- You are receiving this mail because: ---
[Issue 3520] std.numeric.CustomFloat horribly broken
http://d.puremagic.com/issues/show_bug.cgi?id=3520
Rob Jacques sandf...@jhu.edu changed:
What|Removed |Added
CC||sandf...@jhu.edu
Severity|normal |regression
--- Comment #3 from Rob Jacques sandf...@jhu.edu 2010-04-08 09:30:55 PDT ---
There seems to be an additional problem with custom float. In DMD 2.039 and
2.042 it doesn't compile. I've developed a hack/patch around this issue.
For example:
CustomFloat!(1, 5, 10) temp;
Error: this for signfractionexponent needs to be type CustomFloat not type
CustomFloat!(1,5,10)
Error: struct std.numeric.CustomFloat!(1,5,10).CustomFloat member
signfractionexponent is not accessible
Error: template instance std.numeric.CustomFloat!(1,5,10) error instantiating
I've been able to reduce the code to a test case
struct CustomFloat(
bool signBit,
uint fractionBits,
uint exponentBits,
//uint bias = (1u (exponentBits - 1)) - 1// This is the problem
CustomFloatFlags flags = CustomFloatFlags.all
)
{
float foo;
float bar() { return foo;}
F get(F)() { return 1; }
}
however, when I try this as independent test case, the bug isn't reproduced.
As a quick patch I've move bias from a template parameter to the struct body as
an enum:
struct CustomFloat(
bool signBit, // allocate a sign bit? (true for float)
uint fractionBits, // fraction bits (23 for float)
uint exponentBits,
//uint bias = (1u (exponentBits - 1)) - 1
CustomFloatFlags flags = CustomFloatFlags.all)
{
enum bias = (1u (exponentBits - 1)) - 1;
...
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[Issue 3520] std.numeric.CustomFloat horribly broken
http://d.puremagic.com/issues/show_bug.cgi?id=3520 --- Comment #4 from Rob Jacques sandf...@jhu.edu 2010-04-08 10:49:06 PDT --- The bit layout of custom float is not IEEE compliant and can't be used to represent half, float nor double types. Here's the correct layout private mixin(bitfields!( uint, fraction, fractionBits, uint, exponent, exponentBits, bool, sign, signBit)); -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email --- You are receiving this mail because: ---
[Issue 3520] std.numeric.CustomFloat horribly broken
http://d.puremagic.com/issues/show_bug.cgi?id=3520 Andrei Alexandrescu and...@metalanguage.com changed: What|Removed |Added Status|NEW |ASSIGNED CC||and...@metalanguage.com AssignedTo|nob...@puremagic.com|and...@metalanguage.com -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email --- You are receiving this mail because: ---
[Issue 3520] std.numeric.CustomFloat horribly broken
http://d.puremagic.com/issues/show_bug.cgi?id=3520
--- Comment #1 from David Simcha dsim...@yahoo.com 2009-11-16 20:15:34 PST ---
Okay, I've gotten a good start on debugging this by pragma'ing the bitfield
code and pasting it in to temporarily get rid of the mixin. The assert failure
is in setting the exponent:
void exponent(uint v){
assert(v = exponent_min);
assert(v = exponent_max); // FAILS
signfractionexponent = cast(typeof(signfractionexponent))
((signfractionexponent ~49152U) | ((cast(typeof(signfractionexponent)) v
14U) 49152U));
}
The problem appears to be overflow in the following code in opAssign:
exponent = cast(typeof(exponent_max))
(value.exponent + (bias - value.bias));
If the result is negative, we get overflow. Instead, this should probably
result in a denormal or something.
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