Simple Fortran Program With Random Numbers

[ƒ(x) → ∞]

I have been busy trying to generate, using FORTRAN's random number generator, random x and y co-ordinates which follow a simple pattern such as x²-100x, but for some reason the FORTRAN compiler prints nothing.

Anybody want to help me with this problem?

	program quadraticdistribution
	implicit none
	integer i
	integer x,y
	real l
	integer seed/-23434567/
c     ************************************
c     intialize the random number
      l=rand(seed)

c     intialize the x and y values
      x=0
      y=0
       
30      do i=1,200
            x=int(100*rand(0))
            y=int(100*rand(0))
        if (x.ge.(y*y-100*y)) goto 30
            Write(*,*) x,y
        enddo
           
           stop
           end

 

[minger]

What compiler are you using? A lot of random stuff I've seen is compiler-specific. As a G95 user, I'm not familiar with your approach.

 

[Mark44]

Since you're not getting any output, it's probably the case that your if statement is preventing the following write statement from executing. I added a write statement right after x and y get set, so you can at least get some output.

The main problem, I believe, is your goto in the middle of your loop. I changed the logic in your if statement so that if x < y^2 - 100y, the code prints the values of x and y. If x >= y^2 - 100y, the code doesn't print anything.

	program quadraticdistribution
	implicit none
	integer i
	integer x,y
	real l
	integer seed/-23434567/
c     ************************************
c     intialize the random number
      l=rand(seed)

c     intialize the x and y values
      x=0
      y=0
       
      do i=1,200
         x=int(100*rand(0))
         y=int(100*rand(0))
         write(*, *) x, y   ; for debugging purposes
         if (x .lt. (y*y-100*y)) 
            Write(*,*) x,y
         endif
        enddo
           
           stop
           end

 

[hamster143]

If y lies between 0 and 100, y^2-100*y is always negative, and the condition x>y^2-100*y is always true.

 

[LudusRex]

Hello, it seems like you are having trouble with your FORTRAN program that generates random numbers with a specific pattern. There could be a few reasons why your program is not working as expected. First, make sure that you have correctly declared your variables and initialized the random number generator. In your program, you have declared the variables for x and y as integers, but you are using the "rand" function which generates real numbers. This could cause issues with your program.

Also, it is recommended to use a different seed value for each run of your program to ensure a different set of random numbers is generated each time. Right now, you have set the seed to a fixed value of -23434567, which may not be ideal.

Another potential issue could be with your loop. Your code suggests that you want to generate 200 pairs of x and y coordinates, but your loop only runs for 30 iterations. This could be due to the "goto 30" statement, which may be causing your loop to repeat the same values.

I suggest reviewing your code and making sure that all variables are correctly declared and initialized, and that your loop is set up to generate the desired number of coordinates. If you are still having issues, please provide more details about the specific problem you are facing, and I would be happy to assist you further. Best of luck with your FORTRAN program!