"Eigenvalues and vectors.vi" produces different results in LV 7.0 and 8.0

[josborne]

I noticed that the "Eigenvalues and vectors.vi" produces different results when used in LV8.0 and LV7.0.

The attached VI is saved in LV7.0.  The default values show the results when this VI is run in LV7.0.

Using the same inputs, try running this VI in 8.0 and you will see the results change.

Anybody have any ideas why that happens?

[Barp · Accepted solution]

John,

In version 7.0, LabVIEW was using a algorithm develop in house to obtain result. Although it would work in several cases, there was cases that this algorithm would not work as expected.

In version 7.1 and later, this LabVIEW start using a LAPACK/BLAS rotines. They are more advanced algorithm that has been used by several matematical software, including MatrixX and MATLAB.

So, since the algorithm has changed between version, you would expect different results, and, most probably, more accurate results.

Did you evaluate if the results are better? Is it failing your algorithm now? 

[josborne]

Thanks Barp.  Good answer.

As long as the new VI is producing correct (but different) results I am OK with that.  The only problem is that we now need to re-write some of our code to accomodate the slightly different performance.  The subVI may be producing better results (I'm not knowledgable enough about it to know for sure right now), but our code is now malfunctioning due to the change.  I will have to have a closer look to see why that is happening. 

Thank you for your help!