Why not give AmdahlCalc a try? You can, if you click this button:

PerfSuite AmdahlCalc

(and then you can read all about it...)


AmdahlCalc is an interactive JavaScript utility that estimates the maximum speedup for parallel programs (given two timings - single-processor and p processors, where you choose p), using Amdahl's Law. The results are shown in tabular form and (optionally) as a column graph.

It also optionally recommends a processor count for the program by minimizing the value:


One way to think about this is that it asks, "what is the cost, in aggregate processor-time, per unit of speedup?". (If the computer was a car, we'd be talking gallons-per-mile). The assumption is that all processors are dedicated to the application and are idle during serial portions of the program. It would be interesting to use different metrics (any ideas?).

Running AmdahlCalc

You'll need a JavaScript-enabled web browser (Netscape Navigator or Internet Explorer versions 4 and higher, Opera, Mozilla, etc) to use AmdahlCalc.

Click here to give it a try - a window will open on your display that is the AmdahlCalc user interface. All you're required to do is to fill in the form with two numbers: your measured or estimated timings for one processor and p processors (by default, p is set to 2, but you can modify that field). Once you've entered the timings and the correct processor count (and specified any other options you'd like), just click on the button labeled "Run AmdahlCalc" and you'll receive the results.

Accessing AmdahlCalc From Your Page

  1. Save this button (right-click on it and select "Save Picture As..." or "Save Image As..." in your browser):


  2. Copy the following text and paste it wherever you want the button to appear on your web page:
    <a href="#" onClick="'','amdahl','scrollbars,status,resizable,width=580,height=640');return false;">
    <img src="amdahlcalc.gif" alt="PerfSuite AmdahlCalc"></a>
    If you name the button something other than "amdahlcalc.gif", use that name instead. If you save it in a different directory than where your web page is located, you'll have to adjust the path in the "img src=" part accordingly.

    If you don't want to use the button, then use the following:

    <a href="#" onClick="'','amdahl','scrollbars,status,resizable,width=580,height=640');return false;">
    PerfSuite AmdahlCalc</a>

National Center for Supercomputing Applications
University of Illinois at Urbana-Champaign