Finding a slow plug-in in ALTRON with the Performance and Internal Info tabs

Frames are being dropped, the actual rate is below the requested value, and your processing graph has ten or twelve nodes. Which one is the culprit? For finding a slow plugin in ALTRON, you don't need to guess or remove nodes one by one. The Performance and Internal Info tabs in the diagnostics panel put the answer on the screen.

The processing graph in ALTRON is a chain of nodes. Each node is a plug-in that takes data from the previous node and passes it to the next. If one of these links is slow, everything behind it waits.

Step 1: overall CPU usage

In the main window you see three indicators: Physical RAM, Virtual RAM and CPU. Each shows total system usage and the program's own usage separately. If CPU is near 100 percent, dropped frames are no surprise. Now you need to find out what is consuming the processor.

Step 2: the Performance tab

This tab is a simple table. The Item column shows the name of each node and the Cpu column its share of the processor. The table refreshes every second. There is also a Ui row showing the share of the user interface itself. If several cameras are open at the same time, the rows of each chain appear under a separate Chain heading with the chain number.

1. Start acquisition with exactly the settings where the problem appeared.
2. Open the Performance tab and wait a few seconds for the numbers to settle. The numbers in the first few seconds after Start are misleading.
3. Find the row whose Cpu value is clearly larger than the rest.
4. Make one change in that node and look at the table again. Only one change at a time.

Step 3: Internal Info to see where data is dropped

The problem isn't always the CPU. Sometimes a node with normal CPU usage leaves data behind. That is what the Internal Info tab is for:

• Count Rate: How many packets pass through each input and output port of each node per second.
• Main / Extra Data Rate: The main data rate in megabytes per second, and the rate of the extra bytes that come along with the data.

The rule is simple: if a node's output rate suddenly drops below its input rate, data is being dropped right there. If you see no image at all, first check whether the Count Rate of the camera's output port is zero.

You've found the slow node. Now what?

• Make its settings lighter. For example, when saving split raw data, a higher Compression makes the file smaller but increases the processing load. Or, in the color correction matrix node of a color area-scan camera, keep Use Lookup Table turned on.
• Put an ImagingInterval in Max rate mode in front of it. This node caps the data throughput rate and discards the rest. In the ready-made area-scan camera graphs you will see it under the name DREG. Its usual place is right before a heavy node or the viewer.
• Check Read Buffer Size. This setting is in the camera panel and defaults to the maximum value. A larger buffer means the USB driver is called less often. If someone has lowered it, set it back. The change takes effect from the next Start.
• Remove unneeded nodes. Every node whose result you don't need takes a share of the CPU.

A mistake we see often

In Max rate mode, ImagingInterval discards excess data. If you place it at the start of the chain, before the saving branch, and Apply to saving too is also checked, the recorded file will have the same low rate. When you need every single frame, place this node only in the display branch or in front of a heavy node that does not need all frames.

For a more general explanation of software profiling, see Wikipedia (English).

If you cannot interpret the Performance table of your own graph, send us a screenshot of it via contact form.