问题
When I run the code below I get an output of 6378136.5 instead of 6378136.3
PROGRAM test
implicit none
real*8 radius
radius = 6378136.3
print*,radius
END
I have read this other link (Precision problems of real numbers in Fortran) but it doesn't explain how to fix this problem.
回答1:
The reason this is happening is not because the variable you are using lacks precision, but because you initialized the value using a single precision number.
Take a look at this answer for a good explanation, and an elegant solution to your problem for any larger programs.
If you just want to solve it quickly, then you only have to change one line:
radius = 6378136.3d0
Though this will still give you a value of 6378136.2999999998 because of floating point precision.
来源：https://stackoverflow.com/questions/42618704/fortran-handling-large-real-numbers-with-precision