c++ - Will instantiating templates in precompiled headers reduce compile times? -


example: include in precompiled header file:

#include <vector>

as few instances of vector, such std::vector, std::vector etc used in project, reduce compile time if instantiate them in precomiled header this:

#include <vector> template class std::vector<float>; template class std::vector<int>;

going further, make sense add dummy functions precompiled headers uses few functions:

namespace pch_detail { inline auto func() {   auto&& v = std::vector<float>{};   v.size();   v.begin();   v.front(); } }

i'm unsure of of how translation units , templates work, seems me if instantiate them in precompiled headers, should mean not need instantiated every .cpp file.

update

tested on real-world code base visual studio 2017 , instantiations of commonly used template classes.

  1. with common templated class instantiated: 71731 ms
  2. without instantiation: 68544 ms

hence, @ least in case, took took more time.

it can make difference yes.

instantiation in translation units can exploit data in precompiled header, , compiler can read more c++ standard library headers.

but have maintain list of instantiations, compile-time optimisation might more trouble it's worth - idea end having opposite effect if have instantiations no longer needed.


Comments

Post a Comment

Popular posts from this blog

php - Vagrant up error - Uncaught Reflection Exception: Class DOMDocument does not exist -

i've set bento/ubuntu-16.04 vagrant box using php 5.6, , getting following error quite few times when try , run shell script: "uncaught reflection exception: class domdocument not exist". i've tried adding following top of script (not together), each no success: "sudo apt-get install php5.6-xml", "sudo apt-get install php5-xml", "sudo apt-get install php-dom" i've tried resetting server "sudo service apache2 restart". does have suggestions?
Read more

vue.js - Create hooks for automated testing -

Image
qa guys complained can't automate frontend testing. because our html looks same outside. lazy hack did this <template> <div :role="$options.name"> ... </div> </template> <script> export default { name: 'vmcomponentname' } </script> which takes name script , applies html. in browser get: <div role="vmcomponentname"> ... </div> line :role="$options.name" goes in every component. is there dry er solutions? please share. additional details i'll explain in details looking for. imagine have vmusercreate form creates user. test case can create user . to automatically test without role, have use following selector: .wrapper > .wrapper > .wrapper > .submit-button the test extremely brittle (will break lot). if use roles can use [role="vmusercreateform"] .submit-button selector. many folds less brittle. so basically, i'm ...
Read more

Add new key value to json node in java -

i have json file : { "id":1, "name":"abc", "addressdetails": { "city":"newyork" } } i wanted add 1 more key-value ("pincode" : "414141") node 'addressdetails'. i tried using : objectmapper mapper = new objectmapper(); jsonnode root = mapper.readtree(new file("d://test.json")); objectnode node = mapper.createobjectnode(); node.with("addressdetails").put("pincode", "414141"); but it's not getting added, there way can ? you can try you should modify file path objectmapper mapper = new objectmapper(); objectnode nodes = mapper.readvalue(new file("d:\\test.txt"), objectnode.class); nodes.with("addressdetails").put("pincode", "414141"); mapper.writer().writevalue(new file("d:\\test.txt"), nodes);
Read more