Databases
StackOverflow2013
Postsdbo
PO
 

Note that there are some explanatory texts on larger screens.

plurals
  1. PO
    primarykey
    data
    text
    <p>Coincidentally I made a speed test recently (filling 10 * 1024 * 1024 ints with rand() ).<br> These are 3 runs, time in nano-seconds </p> <pre><code>vect[i] time : 373611869 vec.at(i) time : 473297793 *it = time : 446818590 arr[i] time : 390357294 *ptr time : 356895778 </code></pre> <p>UPDATE : added stl-algorithm std::generate, which seems to run the fastest, because of special iterator-optimizing (VC++2008). time in micro-seconds.</p> <pre><code>vect[i] time : 393951 vec.at(i) time : 551387 *it = time : 596080 generate = time : 346591 arr[i] time : 375432 *ptr time : 334612 </code></pre> <p>Conclusion : Use standard-algorithms, they might be faster than a explicit loop ! (and also good practice) </p> <p>Update : the above times were in a I/O-bound situation, I did the same tests with a CPU-bound (iterate over a relatively short vector, which should fit in cache repeatedly, multiply each element by 2 and write back to vector)</p> <pre><code>//Visual Studio 2008 Express Edition vect[i] time : 1356811 vec.at(i) time : 7760148 *it = time : 4913112 for_each = time : 455713 arr[i] time : 446280 *ptr time : 429595 //GCC vect[i] time : 431039 vec.at(i) time : 2421283 *it = time : 381400 for_each = time : 380972 arr[i] time : 363563 *ptr time : 365971 </code></pre> <p>Interestingly iterators and operator[] is considerably slower in VC++ compared to for_each (which seems to degrade the iterators to pointers through some template-magic for performance).<br> In GCC access times are only worse for at(), which is normal, because it's the only range-checked function of the tests. </p>
    singulars
    1. This table or related slice is empty.
    1. POC++ STL: Which method of iteration over a STL container is better?
      singulars
      1. PTQuestion
    1. PTAnswer
    1. USqwerty
    1. USqwerty
    plurals
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    2. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    1. COBarely any statistical difference. Anything about 10% won't have an impact when an actual program is actually in use unless this is in a freqiently used tight loop. A cache miss, and the time would be equal
      singulars
      1. PO
      1. USRobert Gould
    2. COIf you define #define _SECURE_SCL 0 #define _SECURE_SCL_THROWS 0 there will be no difference between pointer and iterator performance.
      singulars
      1. PO
      1. USVadim Ferderer
 

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