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LouP12-Amethyst
12-Amethyst
March 2, 2024
Solved

mathcad 11.2a symbolic bug?

  • March 2, 2024
  • 3 replies
  • 1562 views

For those who still use it, I encountered some strange behavior in the symbolic operations of mathcad 11.2a. In my decades of using mathcad, I find it hard to believe I hadn't seen this before. Using a unary negative sign in front of a vector evaluation seems to work as expected both numerically and symbolically. However, if the unary negative vector is added to another vector of the same size, the result is a nested array.

 

I can't figure out what is going on. Am I just missing some expected behavior, or is this a bug?

 

Lou

Best answer by LucMeekes

Hi Lou,

 

Confirmed.

LucMeekes_0-1709404138571.png

 

Negating a vector in this case behaves as though the vector is transformed into a nested vector, where each of the elements becomes a single element vector (with the negated element value.

Although...:

LucMeekes_1-1709404248958.png

seems to work OK.

I think it's a bug. But it will not be fixed.

 

Success!
Luc

3 replies

W
Werner_E25-Diamond I
25-Diamond I
March 2, 2024

I don't have MC11 installed and when I open your file with MC15, the strange effect is not seen, all is as expected.

Looks like in MC11 the vector with the unary minus is implicitly vectorized for some reason when evaluated symbolically.
Especially strange because usually the symbolic needs explicit vectorization in expressions where a numeric evaluation applies implicit vectorization on its own.

Maybe Luc, who still uses MC11, can shed some light on this.

L
LucMeekes23-Emerald IVAnswer
23-Emerald IV
March 3, 2024

Hi Lou,

 

Confirmed.

LucMeekes_0-1709404138571.png

 

Negating a vector in this case behaves as though the vector is transformed into a nested vector, where each of the elements becomes a single element vector (with the negated element value.

Although...:

LucMeekes_1-1709404248958.png

seems to work OK.

I think it's a bug. But it will not be fixed.

 

Success!
Luc

    L
    LucMeekes23-Emerald IV
    23-Emerald IV
    March 3, 2024

    The bug has been in there at least since Mathcad 2000:

    LucMeekes_0-1709462146069.png

    LucMeekes_1-1709462357101.png

    The error is a 'no symbolic solution was found', most probably due to the fact that you cannot apply simple arithmetic to a nested matrix.

    Considering that Werner doesn't see it happening in Mathcad 15, I think it is related to (the interfacing with) Maple.

     

    Luc

      L
      LouP12-AmethystAuthor
      12-Amethyst
      March 3, 2024

      Thanks Luc.

       

      Good to know it's not just a mind trick on me. At least the behavior is obvious enough that it's unlikely to get by unnoticed; we are aware of it now (and knowing it's not going to change). I'll still stick by my 11.2a.

       

      Lou

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