ThreadBack: comments

Author: fchn289

src/thread/AsyncBack.hpp

@@ -35,7 +35,6 @@
 //   * AsyncBack is for normal/most scenario, may NOK for huge threads, high throughput, etc
 //   * ONLY call AsyncBack in main-thread
 //
-//
 // - Use-safe: yes with condition:
 //   . not support TOO many threads (used-up thread resource; impossible in most/normal cases)
 //   . lower performance than eg thread pool (but simpler impl than thread pool)
@@ -51,7 +50,6 @@
 //   . no duty to any unsafe behavior of MT_TaskEntryFN & TaskBackFN (eg throw exception)
 //     . MT_TaskEntryFN & TaskBackFN shall NOT throw exception
 //     . they can try-catch all exception & leave rlib simple/focus
-//
 // - support multi-thread
 //   . MT_/mt_ prefix: yes
 //   . others: NO (only use in main thread - most dom lib code shall in main thread - simple & nsesilbe)

src/thread/ThPoolBack.hpp

@@ -4,16 +4,16 @@
  * SPDX-License-Identifier: BSD-3-Clause
  */
 // ***********************************************************************************************
-// Why:
-// - alt AsyncBack by limit thread# (limited resource) but may wait more time for free thread
-// - avoid create/destroy thread, 10~100 faster than AsyncBack
-// - code more complex than AsyncBack
+// - Why:
+//   . alt AsyncBack by limit thread# (limited resource) but may wait more time for free thread
+//   . avoid create/destroy thread, 10~100 faster than AsyncBack
+//   . code more complex than AsyncBack
 //
-// Use-safe: yes with condition:
-// - not support TOO many tasks that exceeds fut_backFN_S_/nDoneTh_/.. (impossible in most/normal cases)
-// - destructor will FOREVER wait all thread finished
-// MT safe: NO (can be used in main thread only)
-// Exception-safe: NO
+// - Use-safe: yes with condition:
+//   . not support TOO many tasks that exceeds fut_backFN_S_/nDoneTh_/.. (impossible in most/normal cases)
+//   . destructor will FOREVER wait all thread finished
+// - MT safe: NO (can be used in main thread only)
+// - Exception-safe: NO
 // ***********************************************************************************************
 #pragma once
 

src/thread/ThreadBack.cpp

@@ -25,7 +25,7 @@ size_t ThreadBack::hdlFinishedTasks(UniLog& oneLog)
         // - async() failure will throw exception -> terminate since compiling forbid exception
         // - valid async()'s future never invalid
         // - valid packaged_task's get_future() never invalid
-        auto&& fut = fut_backFN->first;
+        auto& fut = fut_backFN->first;
         // HID("(ThreadBack) nHandled=" << nHandledTask << '/' << nFinishedTask
         //     << ", valid=" << fut.valid() << ", backFn=" << &(fut_backFN->second));
         if (fut.wait_for(0s) == future_status::ready)

src/thread/ThreadBack.hpp

@@ -7,10 +7,6 @@
 // - Why this class:
 //   . support both async() & thread pool
 //   . common here, special in AsyncBack or ThPoolBack
-//
-// - why SafePtr
-//   . thread can ret any type data include bool
-//   . safe convert from SafePtr<void> to correct data
 // ***********************************************************************************************
 #pragma once
 
@@ -72,3 +68,7 @@ class ThreadBack
 // 2024-08-05  CSZ       - nDoneTh_ to improve iteration of fut_backFN_S_
 //                       - MT_TaskEntryFN ret SafePtr<void> instead of bool
 // ***********************************************************************************************
+// - why SafePtr
+//   . thread can ret any type data include bool
+//   . simpler than using MtQ to ship rsp back to main thread
+//   . safe convert from SafePtr<void> to corresponding data

ut/thread/ThPoolBackTest.cpp

@@ -21,7 +21,7 @@ TEST_F(ThPoolBackTest, invalid_maxThread)
 // ***********************************************************************************************
 TEST_F(ThPoolBackTest, performance)
 {
-    const size_t maxThread = 10;  // github ci can afford 10 (1000+ slower than belinb03)
+    const size_t maxThread = 100;  // github ci can afford 100 (1000+ slower than belinb03)
 
     ThPoolBack thPoolBack(maxThread);
     auto start = high_resolution_clock::now();

ut/thread/ThreadBackTest.hpp

@@ -96,7 +96,7 @@ TEST_F(THREAD_BACK_TEST, GOLD_entryFnResult_toBackFn_withoutTimedWait)
         ));
     }
 
-    // REQ: no timedwait() but keep asking
+    // REQ: no timedwait() but keep asking; cost most time in CI
     for (size_t nHandled = 0; nHandled < maxThread; nHandled += threadBack_.hdlFinishedTasks())
     {
         INF("nHandled=" << nHandled);