AutoCAD – Page 4 – Outside The Box

Simplifying the problem: divide and conquer

When a customer reports a drawing-specific issue, the next stage in simplifying the problem is to eliminate all drawing content that has no bearing on the problem. Unless the drawing object that causes the problem is obvious and can be immediately ascertained, I use the divide-and-conquer method to zero in on the cause.

To divide and conquer an AutoCAD drawing, I start by getting a quick feel for what is in the drawing and how it is structured (I use Periscope for this; in fact I originally wrote Periscope for this purpose). The general approach I use is to eliminate roughly one half of the drawing at a time by erasing an arbitrary half, then checking to see whether the problem still exists in the remaining half. Doing this reliably requires some care.

If the drawing has layouts, I start by erasing all layouts except model space. I then save the new file with a new filename, close AutoCAD, restart, open the last file, and test to see whether the problem still exists. If the problem went away, I go back to the original file and start over, erasing everything in model space, then repeat the saveas/close/reopen sequence. Once I pin the problem down to a specific layout (or layouts), I start working on individual drawing entities.

A typical iteration consists of erasing roughly half the drawing entities, then checking whether the problem persists. If the problem goes away, back up and erase the other half, otherwise continue. Entities can be erased either by selection or using QSELECT. If the drawing consists of entities nested inside blocks, I first try erasing the block references; if the problem goes away, I back up and use BEDIT to erase part of the block content.

While going through these iterations, I sprinkle in a periodic purge (using SuperPurge, of course) to remove hidden and invisible objects that become unreferenced as visible entities are erased. I continue this process until I have a drawing file cleaned of everything except the bare minimum needed to reproduce the problem. Often, but not always, that means a drawing file with a single visible entity in it.

The key to success is being methodical and saving with incremented filenames so that it’s easy to back up a step and start over when the problem disappears. Closing and restarting AutoCAD between each iteration helps ensure that the test is not influenced by erased objects remaining in memory. With experience and a bit of skill in correctly guessing where to look, I’ve learned that almost all drawing-specific problems can be narrowed down to the bare minimum in 5 to 10 iterations.

Simplifying the problem: is it the drawing?

One type of support request that I occasionally receive from CADVault users goes something like “when I create a vault, AutoCAD crashes”. I’ve learned that problems like this are usually drawing-specific, so before going any further in simplifying the problem I ask the customer to check whether the problem occurs in an empty drawing. But there’s a trick to this.

The problem is that “empty drawing” is too nebulous. No drawing is completely empty, and in any case, even drawings with no visible geometry can be far from empty. What I really want to test is whether the problem occurs with a drawing that is as nearly empty as possible. To achieve that, I ask the customer to perform the test on “a new drawing created from scratch, with no template”.

The extra “no template” instruction is necessary because just creating a new drawing will bring in any flotsam and jetsam saved in the default template drawing, which could affect the results.

[Side note: it is my experience that many template drawings contain a lot of invisible junk that does nothing but slow things down. If you’re curious about your own templates, open them and use my shareware SuperPurge tool to see what all they contain. You may be surprised.]

If the steps for reproducing the problem are such that they require some visible geometry, I ask the customer to draw a unit circle at the origin in a new “no template” drawing.

If the problem still occurs in a minimal drawing, then it is not drawing-specific; otherwise the next step is to divide and conquer the drawing to narrow things down further.

The art of simplifying the problem

One of the most important skills in resolving technical problems is not problem solving, but problem definition. Stripping a problem down to its essence often makes the solution obvious. I think this is generally true, but especially true in my experience with software tech support and tracking down software bugs.

The first stage in problem simplification is to document a set of steps that consistently reproduces the problem. These steps must be detailed enough so that someone else can use them to reproduce the problem, including a description of exactly what the problem is. Often this is the most difficult step, either because the problem doesn’t happen consistently, or because the problem description lacks detail.

The second stage is to try eliminating unnecessary steps with the goal of determining the bare minimum steps needed to reproduce the problem. If the problem is drawing-specific, this stage includes stripping everything out of the drawing except the bare minimum needed. This is often very time consuming, but almost always a worthwhile investment because it can eliminate a lot of potential dead ends in tracking down the ultimate cause. Often, this stage requires some trial and error.

The third stage is determining the exact cause and source of the problem. In my experience, even problems that at first appear very complicated can almost always be boiled down to just a few steps with a minimal amount of data.

Finally, in stage four the problem has to be solved, of course!

In future posts, I’ll share some tips and techniques that I use to simplify software problems.

Disable AutoCAD InfoCenter

Over the years, I and others have provided instructions for turning off the AutoCAD InfoCenter (or Communication Center in older versions). The instructions are different depending on the AutoCAD version. To make things simple, I decided to roll them all up into a single one-size-fits-all MSI file that disables InfoCenter for any and all versions of AutoCAD or AutoCAD LT in one fell swoop.

The AcadInfoCenterOff.msi file on the ManuSoft Freebies page contains a custom action that disables InfoCenter during installation. Uninstall restores all previous settings. No actual files are installed, as all changes are made in the registry. Packaging the custom action into an MSI is just a convenient way to ensure that you can uninstall in the future from Windows Control Panel even long after the MSI is lost or forgotten.

Why would you want to disable the InfoCenter? Faster startup, for one. Fewer crashes and lockups, for another. This feature of AutoCAD actually starts an invisible background task that runs as a separate process (named either WSCommCntr1.exe or WSCommCntr2.exe), which establishes inter-process communication with the running AutoCAD. This type of inter-process communication channel is notoriously unreliable, and it’s not unusual to see the background task orphaned in memory after AutoCAD closes in an unusual way, sometimes consuming a lot of CPU cycles and sometimes preventing an AutoCAD restart until it is forcibly ended.

QuikPik 4.1 Adds Classic Title Bar Feature

Those of you with bad eyesight (and the rest of us throwbacks) will appreciate the new ‘Classic title bar’ feature in QuikPik 4.1. This new feature addresses AutoCAD 2009 and later versions of AutoCAD with the fancy schmancy title bar and menu bar.

Out-of-the-box (not customizable):

QuikPik ‘Classic title bar’ (Windows 7 Aero Theme):

QuikPik ‘Classic title bar’ (Windows 7 Classic Theme):

If you already own a QuikPik license, you can get the new version by logging in and downloading it again from the link in your order detail. If you don’t own QuikPik yet, try it out by installing the shareware version — and if you like it, buy it!