This field allows to set the iterative solver precision. We remind that for the 
time being, the solver used in SYRTHES
 is based on a preconditionned conjugate gradient.
It is therefore a positive real number. The smaller the number 
the more costly the calculation. By default, it has been set to 
10-6, which is generally a good tradeoff between precision and cost. 
 
In fact, to drive a calculation, user can play with two parameters:
-  the solver precision 
-  the maximum number of iterations in the solver
- 
When a calculation appears to be  too long, 
in some cases, it may be interesting 
to increase slightly this real number (for example to 10-5)
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 SYRTHES version   : VERSION_SYRTHES
 Name help file  : lineEdit_43.html
 I. Rupp, C. Peniguel  -  may 2014
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