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Solution diverging on using double precision

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Old   January 22, 2013, 04:11
Default Solution diverging on using double precision
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Hi,

I have an incompressible Navier Stokes code that was working fine as long as I was using single precision. When I converted to double precision, the residues are very high. Why is this happening?

Thanks!
Qrie
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Old   January 22, 2013, 12:29
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Martin Hegedus
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A bug in your code?

Sometimes issues like the following may occur

if (xx == 0.0) {
then do something
}

Under single precision this might work but double does not if xx is very small but not equal to 0.0, for example xx=1.0e-12. Single precision would round value to zero. Error tolerances should be used.

if (abs(xx) < 1.0e-8) {
then do something
}
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Old   January 23, 2013, 00:11
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That helps! Thank you!
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