Spreadsheet calculation Demo

Build and run with

g++ -x c++ -std=gnu++17 -O2 -Wall -pedantic -pthread task.cxx
./a.out input.txt >output.txt

To use thread sanitizer, build with

clang++ -x c++ -std=gnu++17 -O1 -pthread -fsanitize=thread -g task.cxx

Restrictions

1. Cell IDs must be: [A-Z][0-9]+, the number in range [0..15777215].

2. Every non-empty line is either:

   • <cellId> = <number> or
   • <cellId> = [±] <cellId> [± <cellId>[ ± <cellId>[ ... ]]], here ± is either + or - sign.

3. No error handling or exception handling.

Improvements

1. Consider using lock-free alternatives for producer-consumer queue. But note happens-before relations: CellData::remote_result set by worker thread must become visible to the main thread after this cell is put to ready_queue.

2. Use more robust thread pool with thread-local task queues.

3. Implement check of CellData::epoch so that the calculated result is discarded if the epoch changed.