NAG Example

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A NAG Sample Program

The following is an example of how to compile, link and run a program which invokes the NAG subroutine libraries. This program finds the complex square root, by invoking the NAG library routine A02AAF, as follows:


*     A02AAF Example Program Text
*
*     Solves X^2 = Y, given Y. 
*     This program returns the complex square root of A + B*I,
*     where I is the square root of -1, and A and B are input.
*     
*     Mark 14 Revised.  NAG Copyright 1989.
*     .. Parameters ..
      INTEGER          NIN, NOUT
      PARAMETER        (NIN=5,NOUT=6)
*     .. Local Scalars ..
      DOUBLE PRECISION XI, XR, YI, YR
*     .. External Subroutines ..
      EXTERNAL         A02AAF
*     .. Executable Statements ..
      WRITE (NOUT,*) 'A02AAF Example Program Results'
*     Skip heading in data file
      READ (NIN,*)
      READ (NIN,*) YR, YI
*
      CALL A02AAF(YR,YI,XR,XI)
*
*
      WRITE (NOUT,*)
      WRITE (NOUT,*) '   YR      YI      XR      XI'
      WRITE (NOUT,99999) YR, YI, XR, XI
      STOP
*
99999 FORMAT (1X,2F6.1,2F9.4)
      END

On the SP systems, Compile with something like:

     xlf a02aaf.f -lnag -o sqrt

(which reads "Run the Fortran compiler, with input in the file named a02aaf.f, using the NAG Libraries, and write the output to a file named sqrt.")

On the Sun E10000:

f77 a02aaf.f -L/libapps/NAG/asliR4/lib -lnag_flsol18da -o sqrt

After compiling, run the output file ["sqrt"], and in response to

     A02AAF Example Program Results

press return once [the first line returned is ignored] and then enter the values of A and B

     3.0    4.0

to obtain the square root of A + B I. For example:

     A02AAF Example Program Results
     
     3.0   4.0
     
     YR    YI    XR       XI
     3.0   4.0   2.0000   1.0000

indicates that the square root of 3 + 4 I (which is 2 + I) has real part 2, and imaginary part 1.