MATLAB Release Notes

Mathematics Upgrade Issues

The issues involved in upgrading from MATLAB 7.0 to MATLAB 7.0.1, in terms of mathematics features, are discussed in the following sections:

• Inconsistent NaN Propagation When Solving Singular Linear Systems on Intel Systems
• funm Now Returns a Different Second Output

Inconsistent NaN Propagation When Solving Singular Linear Systems on Intel Systems

In previous releases, when you solved n-by-n linear systems Ax=b using x = A\b, where A is singular or contains NaN, the computed result x often contained NaN. In Version 7.0.1, the same command might return 0 in x, due to the way the Intel® Math Kernel Library (MKL) implementation of the BLAS handles this operation. Code that relies on the result containing NaN should check for the following warnings instead:

• For singular A, an existing warning is issued.

• x = [1 2; 0 0]\[1; 0]
  Warning: Matrix is singular to working precision.
  x =
  
       1
       0
  

• For A that contains NaN, a new warning message is issued.

• x = [1 2; 0 NaN]\[1; 0]
  Warning: Matrix is singular, close to singular or badly scaled.
  Results may be inaccurate. RCOND = NaN.
  x =
  
       1
       0
  

funm Now Returns a Different Second Output

Prior to Release 14, the second output of the function funm was an error estimate that was sometimes inaccurate. In Release 14, Version 7.0, the second output was replaced by an exit flag that indicates whether the computation was successful. Code that was created prior to Release 14, which uses the second output of funm, might not work correctly in Version 7.0 or later.

Publishing

Programming Upgrade Issues

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