Beefy Boxes and Bandwidth Generously Provided by pair Networks
No such thing as a small change
 
PerlMonks  

comment on

( #3333=superdoc: print w/replies, xml ) Need Help??
As quick googling shows, default data type for numpy is 32-bit "single precision" "float"

Are you really sure? I was surprised by your claim that numpy use a default C float. I am a longtime Perl and C hacker and no python expert. But I view the C float type as kind of archaic I use many math libs and the trend is to go past the C double. It would be surprising for a modern lib like numpy to use such a default. Also float() in python means floating point not C float.

Note that I do not really care if tool X is faster that tool Y when the sun, jupiter and the moon are aligned. But I did a bit of web search and could not _quickly_ come up with a definite answer! so I decided to check. Seems that numpy default is a C double:

% steph@kerangi (/tmp/cpanm_t.d) % % python3.8 -c 'import math as m; print(m.sin(float(1)))' 0.8414709848078965 % steph@kerangi (/tmp/cpanm_t.d) % % python3.7 Python 3.7.7 (default, Apr 10 2020, 07:59:19) [GCC 9.3.0] on cygwin Type "help", "copyright", "credits" or "license" for more information. >>> import numpy as np >>> np.float <class 'float'> >>> np.float64 <class 'numpy.float64'> >>> np.float32 <class 'numpy.float32'> >>> print(np.sin(float(1))) 0.8414709848078965 >>> print(np.sin(np.float64(1))) 0.8414709848078965 >>> print(np.sin(np.float32(1))) 0.84147096 >>>

I think that PDL is really a fantastic piece of software and that it is pretty fast. One possible pitfall, common to all C extensions to Perl, is to go back and forth too many times between Perl and C as that can make a computation much slower. It is often possible to avoid it.

hth cheers --sgt

In reply to Re^2: Perl PDL slower than python numpy by sgt
in thread Perl PDL slower than python numpy by fanasy

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post; it's "PerlMonks-approved HTML":



  • Are you posting in the right place? Check out Where do I post X? to know for sure.
  • Posts may use any of the Perl Monks Approved HTML tags. Currently these include the following:
    <code> <a> <b> <big> <blockquote> <br /> <dd> <dl> <dt> <em> <font> <h1> <h2> <h3> <h4> <h5> <h6> <hr /> <i> <li> <nbsp> <ol> <p> <small> <strike> <strong> <sub> <sup> <table> <td> <th> <tr> <tt> <u> <ul>
  • Snippets of code should be wrapped in <code> tags not <pre> tags. In fact, <pre> tags should generally be avoided. If they must be used, extreme care should be taken to ensure that their contents do not have long lines (<70 chars), in order to prevent horizontal scrolling (and possible janitor intervention).
  • Want more info? How to link or or How to display code and escape characters are good places to start.
Log In?
Username:
Password:

What's my password?
Create A New User
Domain Nodelet?
Chatterbox?
and the web crawler heard nothing...

How do I use this? | Other CB clients
Other Users?
Others rifling through the Monastery: (3)
As of 2021-12-04 19:56 GMT
Sections?
Information?
Find Nodes?
Leftovers?
    Voting Booth?
    R or B?



    Results (30 votes). Check out past polls.

    Notices?