Databases
StackOverflow2013
Postsdbo
POWhy does trivial loop in python run so much slower than the same in C++? And how to optimize that?
 

Note that there are some explanatory texts on larger screens.

plurals
  1. POWhy does trivial loop in python run so much slower than the same in C++? And how to optimize that?
    primarykey
    data
    text
    <p>simply run a near empty for loop in python and in C++ (as following), the speed are very different, the python is more than a hundred times slower.</p> <pre class="lang-py prettyprint-override"><code>a = 0 for i in xrange(large_const): a += 1 </code></pre> <pre class="lang-c prettyprint-override"><code>int a = 0; for (int i = 0; i &lt; large_const; i++) a += 1; </code></pre> <p>Plus, what can I do to optimize the speed of python?</p> <p>(Addition: I made a bad example here in the first version of this question, I don't really mean that a=1 so that C/C++ compiler could optimize that, I mean the loop itself consumed a lot of resource (maybe I should use a+=1 as example).. And what I mean by how to optimize is that if the for loop is just like a += 1 that simple, how could it be run in the similar speed as C/C++? In my practice, I used Numpy so I can't use pypy anymore (for now), is there some general methods for making loop far more quickly (such as generator in generating list)? )</p>
    singulars
    1. PO
      singulars
      1. PTAnswer
    1. This table or related slice is empty.
    1. PTQuestion
    1. USchentingpc
    1. USchentingpc
    plurals
    1. PL
      singulars
      1. LTLinked
    2. PL
      singulars
      1. LTLinked
    3. PL
      singulars
      1. LTDuplicate
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. PO
      singulars
      1. PTAnswer
    2. PO
      singulars
      1. PTAnswer
    3. PO
      singulars
      1. PTAnswer
    1. VO
      singulars
      1. POWhy does trivial loop in python run so much slower than the same in C++? And how to optimize that?
      1. This table or related slice is empty.
      1. VTUpMod
    2. VO
      singulars
      1. POWhy does trivial loop in python run so much slower than the same in C++? And how to optimize that?
      1. This table or related slice is empty.
      1. VTDownMod
    3. VO
      singulars
      1. POWhy does trivial loop in python run so much slower than the same in C++? And how to optimize that?
      1. This table or related slice is empty.
      1. VTUpMod
    1. CORelated : http://stackoverflow.com/questions/3033329/why-are-python-programs-often-slower-than-the-equivalent-program-written-in-c-or
      singulars
      1. POWhy does trivial loop in python run so much slower than the same in C++? And how to optimize that?
      1. USAshwini Chaudhary
    2. COCould the C code be optimised away?
      singulars
      1. POWhy does trivial loop in python run so much slower than the same in C++? And how to optimize that?
      1. USAlex K.
    3. COTry `volatile int a;` in the C version, to prevent the loop being removed.
      singulars
      1. POWhy does trivial loop in python run so much slower than the same in C++? And how to optimize that?
      1. USMike Seymour
 

Querying!

 
Guidance
A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload