Re: PDL datatype

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Re^2: PDL datatype by nickschurch (Acolyte) on Nov 29, 2007 at 04:21 UTC
Hmmmm... thats interesting moklevat.... When I do what you did I get a non truncated numbers! I did a few tests and take a look at this: [njs@localhost Shu_Hardness_Ratios]$ perldl perlDL shell v1.33 PDL comes with ABSOLUTELY NO WARRANTY. For details, see the file 'COPYING' in the PDL distribution. This is free software and you are welcome to redistribute it under certain conditions, see the same file for details. ReadLines, NiceSlice, MultiLines enabled Reading PDL/default.perldlrc... Found docs database /usr/lib64/perl5/site_perl/5.8.8/x86_64-linux-thre +ad-multi/PDL/pdldoc.db Type 'help' for online help Type 'demo' for online demos Loaded PDL v2.4.3 Note: AutoLoader not enabled ('use PDL::AutoLoader' recommended) perldl> $x=50137.685706 perldl> print $x 50137.685706 perldl> $x=pdl(50137.685706) perldl> print $x 50137.685706 perldl> $x=zeroes(1) perldl> use PDL::NiceSlice perldl> $x(0) .= 50137.685706 perldl> print $x [ 50137.686] perldl> $x = rcols "bursts.txt" Reading data into piddles of type: [ Double ] Read in 33 elements. perldl> print $x [ 50093.199 50094.308 50954.953 51767.383 51958.219 52005.696 52 +005.763 52142.188 52422.043 52459.414 52482.509 52693.953 52752 +.918 52836.803 52837.198 53107.974 53125.429 53141.53 53198.49 +5 53243.578 53489.381 53603.709 53661.37 53724.982 53724.983 +53864.724 53882.002 53969.248 54224.674 54225.636 54304.474 543 +04.539 54366.513] [download] So if you type the number in straight its no problem, but if you read it from a file using rcols, or if you define a piddle and then put the number into the pre-existing piddle, then it truncates the number! I wonder why it does this? In the PDL manual 'double' is the biggest data type listed so I on;y really understand why creating a piddle with this number in works one way and not another - or how to fix it. I'd love to give you an example of the previous code it was failing in but I've re-written that with my aforementioned inelegant work around.	[reply] [d/l]
Re^3: PDL datatype by etj (Priest) on Jun 07, 2022 at 03:45 UTC
PDL::Core (which stringifies ndarrays) uses these variables: `$PDL::floatformat = "%7g"; # Default print format for long numbers $PDL::doubleformat = "%10.8g";` [download] And when it is stringifying, as you asked it to do, it uses the values of those. The above is the current (2.080) values, but those have been the same since 2.002 back in 1999. However, `printf`'s `g` format treats the precision (the number after the ".", here 8) like so: The precision specifies the number of significant digits. 50137.686 has 8 significant digits. To change this behaviour, just assign a different value to e.g. `$PDL::doubleformat`. The way I checked the above was my usual technique: use `git log -p -w` and text-search for a relevant string, here "floatformat".	[reply] [d/l] [select]
Re^3: PDL datatype by moklevat (Priest) on Nov 29, 2007 at 21:12 UTC
It turns out it may not be so interesting now that my head is on a bit straighter. Assigning `$x=50137.585706` does not create a piddle, as I would have known if I had bothered to `print info($x)`. I previously looked into adding a new types when the topic of using BigInts in piddles came up a while back, but I had to get back to my actual work. It may be that creating a new type would get you where you want to go.	[reply] [d/l] [select]
Re^4: PDL datatype by etj (Priest) on Jun 07, 2022 at 04:14 UTC
Adding a new type, as linked above, is a matter of creating extra options in the various places where PDL types live: conversion functions in Perl-land, type-specifiers for various PDL functions in Perl-land, type-qualifiers in PP function signatures, etc. Until about 2.035, it took extra manual stuff to hook up further types, including the (it turned out unnecessary) manually-hardcoded casting between various C types (it turned out the C standard and compiler can handle that all 100% fine). With the changes there, those manual activities became minimal, which made it easy(ish) to add further C types like C99 complex numbers, the rest of the integer types, and long doubles. However, and this is quite important, PP only provides text-expansion of provided `Code` (etc) chunks into parts of `switch` statements inside the various functions that make up the API of a PDL operation. The expanded text still needs to compile as C. This would mean that to support big ints, or MPFR, something would need to turn atomic C operations on C atomic-type (as I am calling them here) numbers (+,-,*,/,etc) into the appropriate version for those non-atomic types. That would involve parsing the actual C and making substitutions. This is not impossible, and using e.g. Pegex would make it manageable, but it would be significant work. On the plus side, it might facilitate moving to using e.g. OpenCL. See https://github.com/PDLPorters/pdl/issues/349 for more and/or to contribute!	[reply] [d/l] [select]
Re^4: PDL datatype by nickschurch (Acolyte) on Dec 03, 2007 at 01:59 UTC
but `$x=pdl(50137.685706)` should create a piddle and, as I showed in my previous post, this works and sucessfully hold the whole number?!	[reply] [d/l]