Databases
StackOverflow2013
Postsdbo
PO
 

Note that there are some explanatory texts on larger screens.

plurals
  1. PO
    primarykey
    data
    text
    <p>I have not any experience related to OpenCL. So mainly my answer is about C++ using.</p> <ol> <li><p><strong>Why cast is necessary?</strong> The cast is necessary, because you're declaring C array <code>properties[]</code> where each element should be of type <code>cl_context_properties</code>. Since cl_platform_id has different type it should be cast to appropriate type, exactly - <code>cl_context_properties</code>. You're using C-style cast that looks like this: (type_to_cast_to)(expression_to_be_cast). If <code>expression_to_be_cast</code> is just a variable like in you case you can omit parentheses around <code>expression_to_be_cast</code>:</p> <p>cl_context_properties properties[] = { CL_CONTEXT_PLATFORM, (cl_context_properties)platforms[0], 0};</p></li> <li><strong>Why is there an extra set of brackets () at the end?</strong> You should use the brackets since variable <code>platform[0]</code> is of type <code>cl::Platform</code> which is not plain type (like int, char, double for example) and <code>cl::Platform</code> class is a wrapper. You should invoke operator() of this class in order to get underlying data of type <code>cl_platform_id</code> that you need. So next code should be simpler: <code>cl_context_properties properties[] = { CL_CONTEXT_PLATFORM, static_cast&lt;cl_context_properties&gt;(platforms[0]()), 0};</code></li> </ol> <p>Here you're doing cast with C++ style cast <code>static_cast</code> which is preferable cast in C++ ( <a href="http://en.cppreference.com/w/cpp/language/static_cast" rel="nofollow">you can read about it here</a> ) of object returned by invocation of <code>operator()</code> on object <code>platforms[0]</code>. The <code>operator()</code> is defined in class <code>cl::detail::Wrapper&lt; T &gt;</code> (<a href="http://kosobucki.pl/cl_doc/classcl_1_1detail_1_1Wrapper.html" rel="nofollow">class reference</a>) which is parent class for class <code>cl::Platform</code></p>
    singulars
    1. This table or related slice is empty.
    1. POOpenCL C++ context properties syntax
      singulars
      1. PTQuestion
    1. PTAnswer
    1. USCommunity
    1. USFedor Nesterenko
    plurals
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. POOpenCL C++ context properties syntax
      singulars
      1. PTQuestion
    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
    3. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTAcceptedByOriginator
    1. CO1) OK, I think I understand the need to cast now - I guess you can't have an array which contains different types, after all. 2) If I compile without the extra brackets you get: `error: invalid cast from type ‘cl::Platform’ to type ‘cl_context_properties {aka long int}’`
      singulars
      1. PO
      1. USbadger5000
    2. COThe parenthesis on the C++ wrapper are to get the native OpenCL object. The operator() is defined to do that. I'd think it might be "(cl_context_properties)(platforms[0]())" though (take the first cl::Platform from the vector, get the OpenCL handle, cast it to cl_context_properties to put it in the array).
      singulars
      1. PO
      1. USDithermaster
    3. CO@Dithermaster, thanks! Both `(platforms[0]())` and `(platforms[0])()` work though
      singulars
      1. PO
      1. USbadger5000
 

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