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Welcome to the OptSched wiki!

This is a place for helpful tips and tricks for working with OptSched as a project developer.

• Compare two files
• Long-running commands over SSH
  • Task queue with screen
• Run a tool on corresponding files between directory structures
• Nanosecond Timing

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Compare files side by side

You could open both files and compare however you want, but there's a tool specifically made for this: vimdiff. vimdiff will show you the differences between the two files, and scrolling will scroll both files simultaneously. To exit, :qa to "Quit All."

Running a long-running command over SSH

Building the benchmark suites take a long time. There are also several long-running tasks which we may need to do. For this, the screen command can be useful.

In it's simplest form, run: screen -q the command to run (e.g. screen -q ninja), or screen -q bash -c '...' for more complex scripts which need redirection or pipes. Ctrl+AD puts the screen into the background, and you can then log out of your ssh session. screen -r resumes.

Building a task queue with screen

More generally, you can have screen work as a task queue and queue up several commands to run after each other. See this SuperUser answer:

startqueue: starts the queuing system.

#!/usr/bin/env bash
screen -d m -S queue

queue: enqueue a command

#!/usr/bin/env bash
screen -S queue -X stuff "$@^M"

Where the ^M is a single special character. In vim in insert mode, produce it by typing Ctrl+V M. You may want to :set list to show the special character.

viewqueue: Look at the screen.

#!/usr/bin/env bash
screen -S queue -r

A more advanced task queue

With a little work, we can make it possible to view what has started/ended in the queue:

startqueue: starts the queuing system.

#/usr/bin/env bash
screen -d -m -S queuerun
screen -d -m -S queueview
screen -S queueview -X stuff "while true; do read; done >/dev/null^M"

queue: enqueue a command

#!/usr/bin/env bash
tmstmp=$(date '+%Y-%m-%d %r-%Z')
screen -S queueview -X stuff "Queue: $tmstmp  $@^M"
screen -S queuerun -X stuff "screen -S queueview -X stuff \"Start:   \$(date '+%Y-%m-%d %r-%Z')  $@\n\"^M"
screen -S queuerun -X stuff "$@^M"
screen -S queuerun -X stuff "screen -S queueview -X stuff \"End:   \$(date '+%Y-%m-%d %r-%Z')  $@\n\"^M"

viewqueue: Look at the queue.

#!/usr/bin/env bash
screen -S queueview -r

viewqueueout: Look at the terminal on which everything is being run.

#!/usr/bin/env bash
screen -S queuerun -r

Again, the ^Ms are a single special character.

Run over corresponding files across mirrored directories

We often have multiple differently-configured run results in directories. As an example, consider a/ and b/ both with 0.log and 1.log. How do we run a tool over the corresponding files a/0.log b/0.log and a/1.log b/1.log?

$ paste -d ' \n' <(find a/ -type f) <(find b/ -type f) | xargs -L1 echo
a/0.log b/0.log
a/1.log b/1.log

You could also just paste -d '\n' and use xargs -L2 instead.

paste -d ' \n' takes the two redirected shell results (<(...)) and zips the lines together; with just '\n', the lines are interleaved. xargs uses stdin as the commandline arguments of what follows it, but -L# tells it to stick to # lines per command invocation.

Nanosecond Timing

If the millisecond timing used by OptSched in its logs is not precise enough, you can upgrade to nanosecond timing (or microsecond) by editing utilities.h to change std::chrono::duration<double, std::milli> to std::chrono::duration<double, std::nano>:

inline Milliseconds Utilities::GetProcessorTime() {
  auto currentTime = std::chrono::high_resolution_clock::now();
  std::chrono::duration<double, std::nano> elapsed = currentTime - startTime;
  return elapsed.count();
}