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REAL*4 significant digits

tsimm3
New Contributor I
‎04-13-2010 11:24 AM
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I am in the process of converting a project from Fortran 9.1 to 11.1. I was able to build the project without any source code changes, but I am getting slightly different results now. For example, using all REAL*4 variables, a number is calculated to be 83.92726 with the new compiler when it was 83.92727 in the older compiler. Is there a compiler option that will produce the same floating point calculations? Or is that seventh digit just not entirely predictable?
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Steven_L_Intel1
Employee
‎04-13-2010 12:28 PM
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REAL*4 is good to 6 digits. 9.1 defaulted to using the "X87" instructions that sometimes gave you more precision than you declared, 11.1 doesn't.
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