hypertimer
Advanced tools
Hypertimer offers time control for simulations. With simulations, it's important to be able to manipulate the time. Typically, simulations are run in discrete time, jumping from event to event in a deterministic manner. And afterwards, a simulation can be played back in continuous time at a faster or slower pace than real-time (depending on the time scale of the simulation). Hypertimer makes it possible to run in hypertime or in discrete time (a discrete event simulation).
Hypertimer offers basic functionality to control time:
getTime(), setTime(), and now().setTimeout(), setInterval(), and setTrigger().These functions are compatible with JavaScript's built-in functions Date.now(), setTimeout(), and setInterval(), but there is an important difference: they can run at a different moment in time and at a different rate.
Hypertimer enables writing code which can be used interchangeably in simulations as well as in real, online application. For example, a processs could predict its future state by running a simulation of itself, given a current state, its own behavior, and a model of the surrounding world.
Hypertimer runs on node.js and on any modern browser (Chrome, FireFox, Opera, Safari, IE9+).
Install via npm:
npm install hypertimer
Install via bower:
bower install hypertimer
var hypertimer = require('hypertimer');
var timer = hypertimer({rate: 1});
timer.setTime(new Date(2014, 0, 1));
<!doctype html>
<html>
<head>
<script src="./dist/hypertimer.min.js"></script>
</head>
<body>
<script>
var timer = hypertimer({rate: 1});
timer.setTime(new Date(2014, 0, 1));
</script>
</body>
</html>
A hypertimer can run in continuous or discrete time, and can run faster or slower than real-time. The speed of a hypertimer can be configured via the option rate, which can be a positive number (to run in continuous time) or the string 'discrete' (to run in discrete time).
// create a hypertimer running ten times faster than real-time
var timer1 = hypertimer({rate: 10});
// retrieve the current configuration
console.log(timer1.config()); // returns an Object {rate: 10}
// create a hypertimer with the default rate (1 by default)
var timer2 = hypertimer();
// adjust the rate later on
timer2.config({rate: 1/2});
// create a hypertimer running in discrete time (time will jump
// from scheduled event to scheduled event)
var timer3 = hypertimer({rate: 'discrete'});
// create a hypertimer running in discrete time and non-deterministic behavior
var timer4 = hypertimer({rate: 'discrete', deterministic: false});
Hypertimer offers functions to get and set time:
var timer = hypertimer();
// set the time at 1st of January 2050
timer.setTime(new Date(2050, 0, 1, 12, 0, 0));
// get the time as Date
console.log(timer.getTime()); // Returns a date, Sat Jan 01 2050 12:00:00 GMT+0100 (CET)
// get the time as timestamp
console.log(timer.now()); // Returns a number, 2524647600000
The time in a hypertimer can be paused. All scheduled timeouts will be paused as well, and are automatically continued when the timer is running again.
var timer = hypertimer();
// pause the timer
timer.pause();
// time stands still here...
console.log(timer.running); // false
// continue again
timer.continue();
// time is running again
console.log(timer.running); // true
Hypertimer has three functions to schedule events:
setTimeout(callback, delay)setTrigger(callback, time)setInterval(callback, interval [, firstTime])interval is a number in milliseconds. Optionally, a firstTime can be provided.On creation, the trigger time of the events is calculated from the delay, interval, and/or firstTime, and the event is scheduled to occur at that moment in time. When the time of the hypertimer is changed via setTime(), trigger time of running timeouts will not be adjusted.
The functions setTimeout(), setTrigger(), and setInterval() return a timeout id, which can be used to cancel a timeout using the functions clearTimeout(), clearTrigger(), and clearInterval() respectively. To cancel all scheduled events at once, the function clear() can be called.
// create a hypertimer running ten times faster than real-time
var timer = hypertimer({rate: 10});
// start the timer at 1st of January 2050
timer.setTime(new Date(2050, 0, 1, 12, 0, 0));
console.log('start', timer.getTime()); // start Sat Jan 01 2050 12:00:00 GMT+0100 (CET)
// set a timeout after a delay
var delay = 10000; // milliseconds (hyper-time)
var id1 = timer.setTimeout(function () {
console.log('timeout', timer.getTime()); // timeout Sat Jan 01 2050 12:00:10 GMT+0100 (CET)
}, delay);
// set a timeout at a specific time
var time = new Date(2050, 0, 1, 12, 0, 20); // time (hyper-time)
var id2 = timer.setTrigger(function () {
console.log('trigger', timer.getTime()); // trigger Sat Jan 01 2050 12:00:20 GMT+0100 (CET)
}, time);
// set an interval
var interval = 5000; // milliseconds (hyper-time)
var firstTime = new Date(2050, 0, 1, 12, 0, 30); // optional first time (hyper-time)
var counter = 0;
var id3 = timer.setInterval(function () {
console.log('interval', timer.getTime()); // interval, 12:00:30, 12:00:35, 12:00:40, etc ...
// cancel the interval after 10 times
counter++;
if (counter > 10) {
timer.clearInterval(id3);
}
}, interval, firstTime);
When running in continuous time (rate is a positive number), scheduled events are triggered at their scheduled time (in hyper-time). When running a simulation, there is no need to wait and do nothing between scheduled events. It is much faster to jump from event to event in discrete time. To create a hypertimer running in discrete time, configure rate as 'discrete'. Hypertimer ensures that all scheduled events are executed in a deterministic order.
In the example below, the application will immediately output 'done!' and not after a delay of 10 seconds, because the timer is running in discrete time and immediately jumps to the first next event.
// create a hypertimer running in discrete time,
var timer = hypertimer({rate: 'discrete'});
var delay = 10000;
timer.setTimeout(function () {
console.log('Timeout A');
timer.setTimeout(function () {
console.log('Timeout B');
}, delay);
}, delay);
// Will immediately output:
// Timeout A
// Timeout B
When performing asynchronous tasks inside a timeout, one needs to create an asynchronous timeout, which calls done() when all asynchronous actions are finished. This is required in order to guarantee a deterministic order of execution. When non-deterministic order is desired, the configuration option deterministic can be set to false.
// asynchronous timeout
timer.setTimeout(function (done) {
// ... do something
done(); // call done when done
}, delay);
An example of using an asynchronous timeout:
// create a hypertimer running in discrete time,
// jumping from scheduled event to scheduled event.
var timer = hypertimer({rate: 'discrete'});
// create an asynchronous timeout, having a callback parameter done
timer.setTimeout(function (done) {
console.log('Timeout A');
// perform an asynchronous action inside the timeout
someAsyncAction(param, function (err, result) {
timer.setTimeout(function () {
console.log('Timeout B');
}, 10000);
// once we are done with our asynchronous event, call done()
// so the hypertimer knows he can continue with a next event.
done();
});
}, 10000);
// Output:
// Timeout A
// (async action is executed here)
// Timeout B
A hypertimer is constructed as:
hypertimer([options])
By default, a new hypertimer runs with real-time speed and time.
Available options:
| Name | Type | Default | Description |
|---|---|---|---|
| rate | number or 'discrete' | 1 | The rate (in milliseconds per millisecond) at which the timer runs, with respect to real-time speed. Can be a positive number, or the string 'discrete' to run in discrete time. |
| deterministic | boolean | true | If true, (default) events taking place at the same time are executed in a deterministic order: in the same order they where created. If false, they are executed in a randomized order. |
Example:
var timer = hypertimer({rate: 10});
running
True when the timer is running, false when paused. See also functions pause() and continue().clear()
Clear all running timeouts.
clearTimeout(timeoutId: number)
Cancel a timeout.
clearInterval(intervalId: number)
Cancel an interval.
clearTrigger(triggerId: number)
Cancel a trigger.
config([options: Object]): Object
Change the configuration options of the hypertimer, and/or retrieve the current configuration. Available options:
rate: number | 'discrete'deterministic: booleancontinue()
Continue the timer when paused. The state of the timer can be retrieved via the property running. See also pause().
getTime(): Date
Returns the current time of the timer as Date. See also now().
The time can be set using setTime(time).
list()
Returns a list with the id's of all running timeouts.
now() : number
Returns the current time of the timer as a number. See also getTime().
pause()
Pause the timer. The state of the timer can be retrieved via the property running. See also continue().
setInterval(callback: Function, interval: number [, firstTime: Date | number])
Trigger a callback every interval. Optionally, a start date can be provided
to specify the first time the callback must be triggered. The function returns an intervalId which can be used to cancel the trigger using clearInterval(). See also setTimeout and setTrigger. Parameters:
callback: Function
Function executed when delay is exceeded.
interval: number
Interval in milliseconds. When interval is smaller than zero or is infinity, the interval will be set to zero and triggered with a maximum rate.
[firstTime: Date | number]
An optional absolute moment in time (Date) when the callback will be triggered the first time. By default, firstTime = now() + interval.
setTime(time: number | Date)
Set the current time of the timer. Can be a Date or a timestamp. To get the current time, use getTime() or now().
setTimeout(callback: Function, delay: number) : number
Set a timeout, which is triggered when the timeout occurs in hyper-time. See also setTrigger and setInterval. The function returns a timeoutId, which can be used to cancel the timeout using clearTimeout(timeoutId). The parameters are:
callback: Function
Function executed when the delay is exceeded
delay: number
The delay in milliseconds. When the delay is smaller or equal to zero, the callback is triggered immediately.
setTrigger(callback: Function, time: Date | number) : number
Set a trigger, which is triggered when the timeout occurs in hyper-time. See also getTimeout. The function returns a triggerId which can be used to cancel the trigger using clearTrigger(). The parameters are:
callback: Function
Function executed when delay is exceeded.
time: Date | number
An absolute moment in time (Date) when the callback will be triggered. When the date is a Date in the past, the callback is triggered immediately.
toString() : String
Return a string representation of the current hyper-time, equal to timer.getTime().toString().
valueOf() : Date
Get the value of the hypertimer, returns the current time of the timer as Date.
Examples can be found here:
https://github.com/enmasseio/hypertimer/tree/master/examples
To build the library from source, clone the project from github
git clone git://github.com/enmasseio/hypertimer.git
To install all dependencies and build the library, run npm install in the
root of the project.
cd hypertimer
npm install
Then, the project can be build running:
npm run build
This generates the files ./dist/hypertimer.js and ./dist/hypertimer.min.js,
which can be used in the browser.
To automatically rebuild on changes in the source files, once can use
npm run watch
To execute tests for the library, install the project dependencies once:
npm install
Then, the tests can be executed:
npm test
To test code coverage of the tests:
npm run coverage
To see the coverage results, open the generated report in your browser:
./coverage/lcov-report/index.html
Copyright (C) 2014 Almende B.V., http://almende.com
Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.
FAQs
Time control for simulations
The npm package hypertimer receives a total of 22 weekly downloads. As such, hypertimer popularity was classified as not popular.
We found that hypertimer demonstrated a not healthy version release cadence and project activity because the last version was released a year ago. It has 1 open source maintainer collaborating on the project.
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