future

问题 Consider the below code: #include <memory> #include <future> using namespace std; template <typename T, typename Work> void Test2(future<T> f, Work w) { async([](future<T> && f, Work w) {}, move(f), move(w)); } int main() { future<int> x = std::async([]()->int{ std::this_thread::sleep_for(std::chrono::microseconds(200)); return 10; }); Test2(std::move(x), [](int x){}); return 0; } The above, fails with the following compiler error: Error 1 error C2664: 'void Test2::::operator ()(std::future<

问题 Consider the below code: #include <memory> #include <future> using namespace std; template <typename T, typename Work> void Test2(future<T> f, Work w) { async([](future<T> && f, Work w) {}, move(f), move(w)); } int main() { future<int> x = std::async([]()->int{ std::this_thread::sleep_for(std::chrono::microseconds(200)); return 10; }); Test2(std::move(x), [](int x){}); return 0; } The above, fails with the following compiler error: Error 1 error C2664: 'void Test2::::operator ()(std::future<

问题 io.grpc.StatusRuntimeException: CANCELLED at io.grpc.Status.asRuntimeException(Status.java:539) at io.grpc.stub.ClientCalls$UnaryStreamToFuture.onClose(ClientCalls.java:439) at io.grpc.internal.ClientCallImpl.closeObserver(ClientCallImpl.java:422) at io.grpc.internal.ClientCallImpl.access$100(ClientCallImpl.java:74) at io.grpc.internal.ClientCallImpl$ClientStreamListenerImpl.close(ClientCallImpl.java:508) at io.grpc.internal.ClientCallImpl$ClientStreamListenerImpl.access$700(ClientCallImpl

问题 I've been having some troubles with TB in the last days. I have a generic variable (let's assume, for example, the external temperature), which measures are acquired at realtime using MQTT and tb-gateway. I also have the variable forecasts for a given future time period, acquired via MQTT from a Python module which performs the forecasting. I wish to plot in the same graph both the data acquired at realtime and the forecasted trend for a given time period (let's say for the next 24 hours),

问题 I have references to n Future instances f1,.....fn . Is it possible to use Future.apply to create a Future that would complete only when at least one of the n Futures completes, without constantly checking their completion status, but instead by some more efficient way, maybe a callback? 回答1: Future.firstCompletedOf(Seq(f1, ..., fn)) Asynchronously and non-blockingly returns a new Future to the result of the first future in the list that is completed. 来源： https://stackoverflow.com/questions

问题 I have references to n Future instances f1,.....fn . Is it possible to use Future.apply to create a Future that would complete only when at least one of the n Futures completes, without constantly checking their completion status, but instead by some more efficient way, maybe a callback? 回答1: Future.firstCompletedOf(Seq(f1, ..., fn)) Asynchronously and non-blockingly returns a new Future to the result of the first future in the list that is completed. 来源： https://stackoverflow.com/questions

问题 I am writing some code where I might need to create an unbounded number of future objects (java.util.concurrent.Future). But I am worried about running out of memory at some point. Couple of questions here: Does the jvm know that once the future has completed, it is not being refernced anywhere and therefore is eligible for GC (even if the thread within which it was created is still alive and running)? Ideally, I wouldn't want to keep track of these futures themselves. But if I do keep the

问题 I have certain flow that runs async using the CompletableFuture , e.g.: foo(...) .thenAccept(aaa -> { if (aaa == null) { break! } else { ... } }) .thenApply(aaa -> { ... }) .thenApply(... So if my foo() returns null (in a future) I need to break very soon, otherwise, the flow continue. For now I have to check for null all the way, in every future block; but that is ugly. Would this be possible with CompletableFuture ? EDIT With CompletableFuture you can define your flow of async tasks, that

问题 Who owns the shared state in futures and promises? In particular who is responsible for the construction and deletion of the shared state in these classes? Or is the shared state supposed to be reference counted? I am not able to get an answer by reading the docs for these on cppreference. The way I was thinking about it the easiest thing to do would be to have the std::promise class be responsible for the creation of the shared state, but then hand it off to the std::future that is fetched

问题 I'm iterating over a vector of structs and processing each struct individually. It looks something like this: for_each(begin(data),end(data),DoTask); //assume "data" is std::vector<DataT> //assume DoTask is a function that takes a DataT by reference The code is significantly slow because DoTask connects to particular websites and analyzes HTML. What would be the best way to speed this up? My goal is to analyze multiple DataTs at the same time. I'm very new to threading, but std::async and std