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single - double precision

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Old   October 10, 2008, 10:21
Default single - double precision
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PC
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Can anyone comment on loss of accuracy (or lack of) using single precision instead of double precision in high pressure castings?
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Old   October 11, 2008, 13:01
Default Re: single - double precision
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Michael Barkhudarov
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In my experience the difference in the results between single and double precision versions are typically minute.

There are some cases, when the difference are significant, but not in casting applications.

In fact, the main reason for the existence of the single precision version of FLOW-3D are the die casting applications. Ten years ago, these were, and still often are, the most computationally and memory intensive problems, often reaching the 2 Gb limit of the addressable memory on 32-bit operating systems. It was more important to be able to mesh a part than maintain the doulbe precision accuracy. Of course, if you can comfortably fit the double precision model on your machine, then you should do so.
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Old   October 14, 2008, 04:39
Default Re: single - double precision
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CK
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Hi please advice if any significant differences in simulation time between single vs double precison version?

Rgds CK
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Old   October 16, 2008, 09:20
Default Re: single - double precision
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Michael Barkhudarov
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Hi Ck,

Not typically. AS far as I understand, the single precision version may run a bit faster (~10%) because it uses less memory, therefore, it has to access memory and refresh cache less often. If this is true, the difference in time will be hardware-dependent.

Of course, if the double precision code uses so much memory that it has to swap some to disk, then the difference in CPU time wil be greater.
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Old   October 16, 2008, 19:28
Default Re: single - double precision
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CK
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Hi Michael Thanks a lot for the input.

Rgds CK
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