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Matrix Auxiliary Vector
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::

	Matrix auxiliary vector = {resid | rand}

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Description / Usage
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This optional card indicates to Aztec how the auxiliary vector r is determined.
Permissible options are:

resid
    The auxiliary vector is set to the initial residual vector, viz. :math:`r = r(0)`.
rand
    The auxiliary vector is filled with random numbers, each in the range
    :math:`[-1,1]`.

If the *Matrix auxiliary vector* card is omitted, the default is **resid.**

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Examples
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Following is a sample card:
::

	Matrix auxiliary vector = rand

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Technical Discussion
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The auxiliary vector is only used for certain iterative linear matrix solution algorithms.

The **rand** option may cause difficulties with initial iterative solver steps because
different processors may have different initial unknown values at shared unknowns.