The Computer Language
Benchmarks Game

mandelbrot Fortran Intel #3 program

source code

! The Computer Language Benchmarks Game
! http://benchmarksgame.alioth.debian.org/
!
! Simon Geard, 6/1/05
! Modified by Waldemar Spomer, 10/1/09: openmp, one I/O

program mandelbrot
	use omp_lib
	implicit none
	integer N, x, y, bit_num, i, incr, width_bytes
	integer(kind=1) byte_acc, state, mask, res, maskbita, maskbitb
	integer(kind=1), parameter :: K0 = 0, K1 = 1
	integer, parameter :: iter = 50
	real*8, parameter  :: limit2 = 4.0d0
	double precision :: absZ1, absZ2, invert
	character(len=8) argv
	complex(kind=8) Z1, Z2, C1, C2
	logical in_mandelbrot
	! Modified to use pointers
	character(len=1), pointer, dimension(:) :: whole_data, pdata
	double precision, dimension(1:2) :: m1, m2 ! for mask
	
	nullify(pdata, whole_data)
	
	call getarg(1,argv)
	read(argv,*) N
	
	allocate(whole_data(N**2/8),STAT=state)
	! Output pbm header
	write(*,'(a)') 'P4'
	write(*,'(i0,a,i0)') N,' ',N
	
	width_bytes = ishft(N,-3)
	invert = 2.0d0/N
	! Modified
	!$omp parallel default(private) shared(whole_data,N,width_bytes,invert)
	!$omp do schedule(dynamic)
	do y=1,N-1
		bit_num = 0
		byte_acc = K0
		! Adopted form c++ example
		pdata => whole_data((y-1)*width_bytes:(y)*width_bytes)
		incr=0
		do x=1,N-1,2
			C1 = cmplx(x*invert-1.5d0,y*invert-1.0d0)
			C2 = cmplx((x+1)*invert-1.5d0,y*invert-1.0d0)
			Z1 = C1
			Z2 = C2
			in_mandelbrot = .true.
			res=3
			do i=1,iter
				
				! Adopted from C/C++ example
				Z1 = Z1**2 + C1
				Z2 = Z2**2 + C2
				
				absZ1 = real(Z1*conjg(Z1))
				absZ2 = real(Z2*conjg(Z2))
				
				if (absZ2 <= limit2 .AND. absZ1 <= limit2) then
					mask = 3
				else if (absZ2 > limit2 .AND. absZ1 <= limit2) then
					mask = 2
				else if (absZ2 <= limit2 .AND. absZ1 > limit2) then
					mask = 1
				else if (absZ2 > limit2 .AND. absZ1 > limit2) then
					mask = 0
				end if
				
				res = iand(res,mask)
				
				if (res==0) exit
			end do
			
			bit_num = bit_num + 2
			byte_acc = ior(ishft(byte_acc,2),res)
			
			if (bit_num == 8) then
				! All bits set so output them
				incr=incr+1
				pdata(incr) = char(byte_acc)
				byte_acc = K0
				bit_num = 0

			end if
		end do
	! End of a row so left-justify the bits we have and output them
	byte_acc = ishft(byte_acc,8-mod(N,8))
	pdata(incr) = char(byte_acc)

	end do
	!$omp end do nowait
	!$omp end parallel
	write(*,*) whole_data
	deallocate(whole_data)
	nullify(pdata, whole_data)
end program mandelbrot
    

notes, command-line, and program output

NOTES:
32-bit Ubuntu one core
Intel(R) Fortran Compiler XE for applications running on IA-32, Version 15.0.2.164 Build 20150121
Copyright (C) 1985-2015 Intel Corporation.  All rights reserved.
FOR NON-COMMERCIAL USE ONLY


Wed, 25 Mar 2015 01:00:02 GMT

MAKE:
/usr/local/src/intel/bin/ifort -O3 -fast -openmp mandelbrot.ifc-3.f90 -o mandelbrot.ifc-3.ifc_run
rm mandelbrot.ifc-3.f90
0.40s to complete and log all make actions

COMMAND LINE:
./mandelbrot.ifc-3.ifc_run 1000

UNEXPECTED OUTPUT 

_out 1000_out differ: byte 14, line 3

(BINARY) PROGRAM OUTPUT NOT SHOWN