I think we may need something like
an option to enable/disable forced
conversion of perl scalars to double
piddles.
--Chris
On Wed, Nov 18, 2015 at 3:03 PM, Chris Marshall <devel.chm...@gmail.com>
wrote:
> Hi Doug-
>
> I think the problem is only when
> a perl scalar is the input to atan().
> The top two cases are the expected
> result. Maybe the logic in the type
> conversion is off. You don't say
> what version of PDL but I see the
> same output from PDL-2.014_02.
>
> --Chris
>
>
>
> On Wed, Nov 18, 2015 at 1:29 PM, Douglas Hunt <dh...@ucar.edu> wrote:
>
>> Hi all: I just noticed a thing which caused me some trouble.
>>
>> The PDL 'atan' function defaults to 'float' precision instead of the
>> more natural 'double':
>>
>> use PDL;
>>
>> my $a1 = atan(double(2379.0)/double(1024.0));
>> my $a2 = atan(float(2379.0)/float(1024.0));
>> my $a3 = atan(2379.0/1024.0);
>>
>> print "$a1, $a2, $a3\n";
>>
>> This prints:
>> 1.1643329321713, 1.1643328666687, 1.1643328666687
>>
>> This feature causes a problem when porting to/from C as the C atan
>> function operates on doubles.
>>
>> I think this traces down to Basic::Math in the math.pd file:
>>
>> my (@ufuncs1) = qw(acos asin atan cosh sinh tan tanh); # F,D only
>> ...
>> my $func;
>> foreach $func (@ufuncs1) {
>> pp_def($func,
>> HandleBad => 1,
>> NoBadifNaN => 1,
>> GenericTypes => ['F','D'],
>> Pars => 'a(); [o]b();',
>> Inplace => 1,
>> Doc => inplace_doc( $func ),
>> Code => code_ufunc($func),
>> BadCode => badcode_ufunc($func),
>> );
>> }
>>
>> Note that GenericTypes isF, D instead of D, F.
>>
>> I would go so far to say that this is a bug, as the default pdl type is
>> double as in:
>>
>> my $pdl = pdl(4,5,6);
>> p $pdl->info
>> PDL: Double D [3]
>>
>> Regards,
>>
>> Doug Hunt
>>
>>
>>
>>
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>>
>
>
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