Question regarding work array: the bigger the better?

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Question regarding work array: the bigger the better?

Postby phymilton » Sat Feb 05, 2005 5:52 pm

Hello,

For most every scalapack or lapack routines, there are usually one or two work array as input argument. And this is a method to caculate the minimum required space for the work array.

My question is: as for each work array, there is a minimum requirement of space, is it the larger the work array (when larger than the minimum), the better the performance. Or just the minimum is the best choice.

Thank you!

Ming @ Ames
phymilton
 
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Postby Julien Langou » Sun Feb 06, 2005 6:30 pm

For most of the routines, the minimum size will not give you good performance.
You want to use a larger size. The question is how large. To know the optimal size for the work space you have to call the routine first with LWORK=-1 (and with all the other parameters set as you intend to use the routine). The optimal size for the WORK array is calculated and stored in WORK(1).

Julien
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