Related
We know we can optimise our code from outside.
We know in fortran programming we define variables first in the program. Then we can take inputs from outside (via read statements) but can we make a small code that take kind of variable from outside.
I.e. if we put in the terminal 4 kind 4(i.e.real(kind =4) ) variable is introduced ie if we put 8 kind 8(i.e real(kind=8) variable is introduced . Is there any way.
I know we can do three separate if loops to define the variables (namely kind 4 , kind 8 ,kind 16 and repeat the program the program three times ).
The code i wrote was for findinding value of y using eulers method.
I want to generalise to any kind and calculate the time taken. I hope this can be done in lesser cumbersome way.
The code I wrote:
program euler
implicit none
real(kind=4)::t,h,y,s,e,r
real(kind=8)::t8,h8,y8,s8,e8,r8
real(kind=16)::t16,h16,y16,s16,e16,r16
integer::k,i
t=0
t8=0
t16=0
y=10
y8=10
y16=10
print *,"enter the kind you want to work with"
read(*,*) k
!so if user writes 4 kind 4 variables would do the work
if(k==4) then
print *,"enter the grid step"
read(*,*) h
r=10*exp(-5.0)
call cpu_time(s)
do i=1,999999999
if(0.le.t.and.t.le.25) then
y=y-h*y/5.0
t=t+h
end if
end do
call cpu_time(e)
print *,"solution is",y
print *,"the error is",(r-y)/r
print *,"time taken in seconds =",e-s
else if(k==8) then
print *,"enter the grid step"
read(*,*) h8
r8=10*exp(-5.0D0)
call cpu_time(s8)
do i=1,999999999
if(0.le.t8.and.t8.le.25) then
y8=y8-h8*y8/5.0
t8=t8+h8
end if
end do
call cpu_time(e8)
print *,"solution is",y8
print *,"the error is",(r8-y8)/r8
print *,"time taken in seconds for kind 8 =",e8-s8
else if(k==16) then
print *,"enter the grid step"
read(*,*) h16
r16=10*exp(-5.0D0)
call cpu_time(s16)
do i=1,999999999
if(0.le.t16.and.t16.le.25) then
y16=y16-h16*y16/5.0
t16=t16+h16
end if
end do
call cpu_time(e16)
print *,"solution is",y16
print *,"the error is",(r16-y16)/r16
print *,"time taken in seconds for kind 16 =",e16-s16
end if
end program euler
But im looking something more smart and less cumbersome.
I don't think this is 100% what you want because there are still three separate subroutines each for a different kind, but they are called using the interface euler which determines which one to use based on the arguments
program SO_Euler
use iso_fortran_env, only : sp=>real32, dp=>real64, qp=>real128, i4=>int32, i8=>int64
implicit none
interface euler
procedure euler_driver_sp, euler_driver_dp, euler_driver_qp
end interface
real(sp), parameter :: r4 = 10*exp(-5.0)
real(dp), parameter :: r8 = 10*exp(-5d0)
real(qp), parameter :: r16 = 10*exp(-5q0)
real(sp) :: h
print *,"enter the grid step"
read(*,*) h
print *, ""
call euler(r4, h)
call euler(r8, h)
call euler(r16, h)
contains
subroutine euler_driver_sp(r,h_in)
real(sp), intent(in) :: r
real(sp), intent(in) :: h_in
real(sp) :: h, y, t
integer(i8) :: s, e, rate
integer :: i
print '(a15,1x,g0)', "kind is ", kind(r)
h = h_in
t = 0
y = 10
call SYSTEM_CLOCK(s,rate)
do i=1,999999999
if(0<=t .and. t<=25) then
y=y-h*y/5
t=t+h
else
exit
end if
end do
call SYSTEM_CLOCK(e,rate)
print '(a15,1x,g0.15)',"solution is", y
print '(a15,1x,g0.15)',"the error is", (r-y)/r
print '(a15,1x,g0.4,1x,a)',"time taken is", real(e-s)/rate,"seconds"
print *, ""
end subroutine
subroutine euler_driver_dp(r, h_in)
real(dp), intent(in) :: r
real(sp), intent(in) :: h_in
real(dp) :: h, y, t
integer(i8) :: s, e, rate
integer :: i
print '(a15,1x,g0)', "kind is ", kind(r)
h = h_in !! convert sp=>dp
t = 0
y = 10
call SYSTEM_CLOCK(s,rate)
do i=1,999999999
if(0<=t .and. t<=25) then
y=y-h*y/5
t=t+h
else
exit
end if
end do
call SYSTEM_CLOCK(e,rate)
print '(a15,1x,g0.15)',"solution is", y
print '(a15,1x,g0.15)',"the error is", (r-y)/r
print '(a15,1x,g0.4,1x,a)',"time taken is", real(e-s)/rate,"seconds"
print *, ""
end subroutine
subroutine euler_driver_qp(r, h_in)
real(qp), intent(in) :: r
real(sp), intent(in) :: h_in
real(qp) :: h, y, t
integer(i8) :: s, e, rate
integer :: i
print '(a15,1x,g0)', "kind is ", kind(r)
h = h_in ! convert sp=>qp
t = 0
y = 10
call SYSTEM_CLOCK(s,rate)
do i=1,999999999
if(0<=t .and. t<=25) then
y=y-h*y/5
t=t+h
else
exit
end if
end do
call SYSTEM_CLOCK(e,rate)
print '(a15,1x,g0.15)',"solution is", y
print '(a15,1x,g0.15)',"the error is", (r-y)/r
print '(a15,1x,g0.4,1x,a)',"time taken is", real(e-s)/rate,"seconds"
print *, ""
end subroutine
end program
here is some sample output of the procedure
enter the grid step
0.000002
kind is 4
solution is .547848604619503E-01
the error is .186920538544655
time taken is .1020 seconds
kind is 8
solution is .673793765102040E-01
the error is .138737586862949E-05
time taken is .7200E-01 seconds
kind is 16
solution is .673793765102226E-01
the error is .138737559174033E-05
time taken is 1.535 seconds
Note that I am compiling in 64bit release mode, and have floating-point model not fast, but strict as well as the option to extend the precision of real constants.
I'm trying to learn Fortran (unfortunately a necessity for my research group) - one of the tasks I set myself was to package one of the necessary functions (Associated Legendre polynomials) from the Numerical Recipes book into a fortran 03 compliant module. The original program (f77) has some error handling in the form of the following:
if(m.lt.0.or.m.gt.1.or.abs(x).gt.1)pause 'bad arguments in plgndr'
Pause seems to have been deprecated since f77 as using this line gives me a compiling error, so I tried the following:
module sha_helper
implicit none
public :: plgndr, factorial!, ylm
contains
! numerical recipes Associated Legendre Polynomials rewritten for f03
function plgndr(l,m,x) result(res_plgndr)
integer, intent(in) :: l, m
real, intent(in) :: x
real :: res_plgndr, fact, pll, pmm, pmmp1, somx2
integer :: i,ll
if (m.lt.0.or.m.gt.l.or.abs(x).gt.1) then
write (*, *) "bad arguments to plgndr, aborting", m, x
res_plgndr=-10e6 !return a ridiculous value
else
pmm = 1.
if (m.gt.0) then
somx2 = sqrt((1.-x)*(1.+x))
fact = 1.
do i = 1, m
pmm = -pmm*fact*somx2
fact = fact+2
end do
end if
if (l.eq.m) then
res_plgndr = pmm
else
pmmp1 = x*(2*m+1)*pmm
if(l.eq.m+1) then
res_plgndr = pmmp1
else
do ll = m+2, l
pll = (x*(2*ll-1)*pmmp1-(ll+m-1)*pmm)/(ll-m)
pmm = pmmp1
pmmp1 = pll
end do
res_plgndr = pll
end if
end if
end if
end function plgndr
recursive function factorial(n) result(factorial_result)
integer, intent(in) :: n
integer, parameter :: RegInt_K = selected_int_kind(20) !should be enough for the factorials I am using
integer (kind = RegInt_K) :: factorial_result
if (n <= 0) then
factorial_result = 1
else
factorial_result = n * factorial(n-1)
end if
end function factorial
! function ylm(l,m,theta,phi) result(res_ylm)
! integer, intent(in) :: l, m
! real, intent(in) :: theta, phi
! real :: res_ylm, front_block
! real, parameter :: pi = 3.1415926536
! front_block = sqrt((2*l+1)*factorial(l-abs(m))/(4*pi*))
! end function ylm
end module sha_helper
The main code after the else works, but if I execute my main program and call the function with bad values, the program freezes before executing the print statement. I know that the print statement is the problem, as commenting it out allows the function to execute normally, returning -10e6 as the value. Ideally, I would like the program to crash after giving a user readable error message, as giving bad values to the plgndr function is a fatal error for the program. The function plgndr is being used by the program sha_lmc. Currently all this does is read some arrays and then print a value of plgndr for testing (early days). The function ylm in the module sha_helper is also not finished, hence it is commented out. The code compiles using gfortran sha_helper.f03 sha_lmc.f03 -o sha_lmc, and
gfortran --version
GNU Fortran (GCC) 4.8.2
!Spherical Harmonic Bayesian Analysis testbed for Lagrangian Dynamical Monte Carlo
program sha_analysis
use sha_helper
implicit none
!Analysis Parameters
integer, parameter :: harm_order = 6
integer, parameter :: harm_array_length = (harm_order+1)**2
real, parameter :: coeff_lo = -0.1, coeff_hi = 0.1, data_err = 0.01 !for now, data_err fixed rather than heirarchical
!Monte Carlo Parameters
integer, parameter :: run = 100000, burn = 50000, thin = 100
real, parameter :: L = 1.0, e = 1.0
!Variables needed by the program
integer :: points, r, h, p, counter = 1
real, dimension(:), allocatable :: x, y, z
real, dimension(harm_array_length) :: l_index_list, m_index_list
real, dimension(:,:), allocatable :: g_matrix
!Open the file, allocate the x,y,z arrays and read the file
open(1, file = 'Average_H_M_C_PcP_boschi_1200.xyz', status = 'old')
read(1,*) points
allocate(x(points))
allocate(y(points))
allocate(z(points))
print *, "Number of Points: ", points
readloop: do r = 1, points
read(1,*) x(r), y(r), z(r)
end do readloop
!Set up the forwards model
allocate(g_matrix(harm_array_length,points))
!Generate the l and m values of spherical harmonics
hloop: do h = 0, harm_order
ploop: do p = -h,h
l_index_list(counter) = h
m_index_list(counter) = p
counter = counter + 1
end do ploop
end do hloop
print *, plgndr(1,2,0.1)
!print *, ylm(1,1,0.1,0.1)
end program sha_analysis
Your program does what is known as recursive IO - the initial call to plgndr is in the output item list of an IO statement (a print statement) [directing output to the console] - inside that function you then also attempt to execute another IO statement [that outputs to the console]. This is not permitted - see 9.11p2 and p3 of F2003 or 9.12p2 of F2008.
A solution is to separate the function invocation from the io statement in the main program, i.e.
REAL :: a_temporary
...
a_temporary = plgndr(1,2,0.1)
PRINT *, a_temporary
Other alternatives in F2008 (but not F2003 - hence the [ ] parts in the first paragraph) include directing the output from the function to a different logical unit (note that WRITE (*, ... and PRINT ... reference the same unit).
In F2008 you could also replace the WRITE statement with a STOP statement with a message (the message must be a constant - which wouldn't let you report the problematic values).
The potential for inadvertently invoking recursive IO is part of the reason that some programming styles discourage conducting IO in functions.
Try:
if (m.lt.0.or.m.gt.l.or.abs(x).gt.1) then
write (*, *) "bad arguments to plgndr, aborting", m, x
stop
else
...
end if
I'm trying to learn Fortran (unfortunately a necessity for my research group) - one of the tasks I set myself was to package one of the necessary functions (Associated Legendre polynomials) from the Numerical Recipes book into a fortran 03 compliant module. The original program (f77) has some error handling in the form of the following:
if(m.lt.0.or.m.gt.1.or.abs(x).gt.1)pause 'bad arguments in plgndr'
Pause seems to have been deprecated since f77 as using this line gives me a compiling error, so I tried the following:
module sha_helper
implicit none
public :: plgndr, factorial!, ylm
contains
! numerical recipes Associated Legendre Polynomials rewritten for f03
function plgndr(l,m,x) result(res_plgndr)
integer, intent(in) :: l, m
real, intent(in) :: x
real :: res_plgndr, fact, pll, pmm, pmmp1, somx2
integer :: i,ll
if (m.lt.0.or.m.gt.l.or.abs(x).gt.1) then
write (*, *) "bad arguments to plgndr, aborting", m, x
res_plgndr=-10e6 !return a ridiculous value
else
pmm = 1.
if (m.gt.0) then
somx2 = sqrt((1.-x)*(1.+x))
fact = 1.
do i = 1, m
pmm = -pmm*fact*somx2
fact = fact+2
end do
end if
if (l.eq.m) then
res_plgndr = pmm
else
pmmp1 = x*(2*m+1)*pmm
if(l.eq.m+1) then
res_plgndr = pmmp1
else
do ll = m+2, l
pll = (x*(2*ll-1)*pmmp1-(ll+m-1)*pmm)/(ll-m)
pmm = pmmp1
pmmp1 = pll
end do
res_plgndr = pll
end if
end if
end if
end function plgndr
recursive function factorial(n) result(factorial_result)
integer, intent(in) :: n
integer, parameter :: RegInt_K = selected_int_kind(20) !should be enough for the factorials I am using
integer (kind = RegInt_K) :: factorial_result
if (n <= 0) then
factorial_result = 1
else
factorial_result = n * factorial(n-1)
end if
end function factorial
! function ylm(l,m,theta,phi) result(res_ylm)
! integer, intent(in) :: l, m
! real, intent(in) :: theta, phi
! real :: res_ylm, front_block
! real, parameter :: pi = 3.1415926536
! front_block = sqrt((2*l+1)*factorial(l-abs(m))/(4*pi*))
! end function ylm
end module sha_helper
The main code after the else works, but if I execute my main program and call the function with bad values, the program freezes before executing the print statement. I know that the print statement is the problem, as commenting it out allows the function to execute normally, returning -10e6 as the value. Ideally, I would like the program to crash after giving a user readable error message, as giving bad values to the plgndr function is a fatal error for the program. The function plgndr is being used by the program sha_lmc. Currently all this does is read some arrays and then print a value of plgndr for testing (early days). The function ylm in the module sha_helper is also not finished, hence it is commented out. The code compiles using gfortran sha_helper.f03 sha_lmc.f03 -o sha_lmc, and
gfortran --version
GNU Fortran (GCC) 4.8.2
!Spherical Harmonic Bayesian Analysis testbed for Lagrangian Dynamical Monte Carlo
program sha_analysis
use sha_helper
implicit none
!Analysis Parameters
integer, parameter :: harm_order = 6
integer, parameter :: harm_array_length = (harm_order+1)**2
real, parameter :: coeff_lo = -0.1, coeff_hi = 0.1, data_err = 0.01 !for now, data_err fixed rather than heirarchical
!Monte Carlo Parameters
integer, parameter :: run = 100000, burn = 50000, thin = 100
real, parameter :: L = 1.0, e = 1.0
!Variables needed by the program
integer :: points, r, h, p, counter = 1
real, dimension(:), allocatable :: x, y, z
real, dimension(harm_array_length) :: l_index_list, m_index_list
real, dimension(:,:), allocatable :: g_matrix
!Open the file, allocate the x,y,z arrays and read the file
open(1, file = 'Average_H_M_C_PcP_boschi_1200.xyz', status = 'old')
read(1,*) points
allocate(x(points))
allocate(y(points))
allocate(z(points))
print *, "Number of Points: ", points
readloop: do r = 1, points
read(1,*) x(r), y(r), z(r)
end do readloop
!Set up the forwards model
allocate(g_matrix(harm_array_length,points))
!Generate the l and m values of spherical harmonics
hloop: do h = 0, harm_order
ploop: do p = -h,h
l_index_list(counter) = h
m_index_list(counter) = p
counter = counter + 1
end do ploop
end do hloop
print *, plgndr(1,2,0.1)
!print *, ylm(1,1,0.1,0.1)
end program sha_analysis
Your program does what is known as recursive IO - the initial call to plgndr is in the output item list of an IO statement (a print statement) [directing output to the console] - inside that function you then also attempt to execute another IO statement [that outputs to the console]. This is not permitted - see 9.11p2 and p3 of F2003 or 9.12p2 of F2008.
A solution is to separate the function invocation from the io statement in the main program, i.e.
REAL :: a_temporary
...
a_temporary = plgndr(1,2,0.1)
PRINT *, a_temporary
Other alternatives in F2008 (but not F2003 - hence the [ ] parts in the first paragraph) include directing the output from the function to a different logical unit (note that WRITE (*, ... and PRINT ... reference the same unit).
In F2008 you could also replace the WRITE statement with a STOP statement with a message (the message must be a constant - which wouldn't let you report the problematic values).
The potential for inadvertently invoking recursive IO is part of the reason that some programming styles discourage conducting IO in functions.
Try:
if (m.lt.0.or.m.gt.l.or.abs(x).gt.1) then
write (*, *) "bad arguments to plgndr, aborting", m, x
stop
else
...
end if
i'm working on a small program for a course in university and i'm almost finished but somehow it doesn't work as i want it to work.
Now, the output file gravity1.dat should give me values unequal to 0. But it doesnt... Somewhere in the last formula where i calculate g(surf), one of the variables is 0. If tried almost everything in my power to correct it but i can't seem to fix it.
program gravity
implicit none
real(8) Lx,Ly,sx,sy,xsphere,ysphere,r,A,rho1,rho2,dx,G
integer np,nel,nelx,nely,i,nnx,nny,j,counter,nsurf
real(8),dimension(:),allocatable :: xcgrid
real(8),dimension(:),allocatable :: ycgrid
real(8),dimension(:),allocatable :: xgrid
real(8),dimension(:),allocatable :: ygrid
real(8),dimension(:),allocatable :: rho
real(8),dimension(:),allocatable :: xsurf, gsurf
real(8),dimension(:),allocatable :: ysurf
nnx=11.
nny=11.
Lx=10.
Ly=10.
nelx=nnx-1.
nely=nny-1.
nel=nelx*nely
np=nnx*nny
sx=Lx/nelx
sy=Ly/nely
xsphere=5.
ysphere=5.
r=3.
nsurf=7 !number of gravimeters
dx=Lx/(nsurf-1.)
!==========================================================
allocate(xgrid(np))
allocate(ygrid(np))
counter=0
do i=1,nnx
do j=1,nny
counter=counter+1
xgrid(counter)=dble(i-1)*sx
ygrid(counter)=dble(j-1)*sy
end do
end do
call write_two_columns(np,xgrid,ygrid,'grid_init1.dat')
!==========================================================
allocate(xcgrid(np))
allocate(ycgrid(np))
counter=0
do i=1,nnx-1
do j=1,nny-1
counter=counter+1
xcgrid(counter)=dble(i-1)*sx+0.5*sx
ycgrid(counter)=dble(j-1)*sy+0.5*sy
end do
end do
call write_two_columns(np,xcgrid,ycgrid,'gridc_init1.dat')
!==========================================================
allocate(rho(nel))
rho1=3000. !kg/m^3
rho2=3200. !kg/m^3
do i=1,nel
if (sqrt((xsphere-xcgrid(i))**2)+((ysphere-ycgrid(i))**2)<r) then
rho(i)=3200.
else
rho(i)=3000.
end if
end do
call write_three_columns(nel,xcgrid,ycgrid,rho,'inclusion1.dat')
!==========================================================
allocate(xsurf(nsurf))
allocate(ysurf(nsurf))
do i=1,nsurf
xsurf(i)=(i-1)*dx
ysurf(i)=ly
end do
call write_two_columns(nsurf,xsurf,ysurf,'surf_init1.dat')
!==========================================================
allocate(gsurf(nsurf))
G=0.000000000066738480 !m^3 kg^-1 s^-2
do i=1,nsurf
do j=1,nel
gsurf(i)=gsurf(i)+(-2.*G*(((rho(i)-rho1)*(ycgrid(counter)-ysurf(i)))/((xcgrid(counter)-xsurf(i))**2.+(ycgrid(counter)-ysurf(i))**2.))*sx*sy)
end do
end do
call write_two_columns(nsurf,xsurf,gsurf,'gravity1.dat')
deallocate(xgrid)
deallocate(ygrid)
deallocate(xcgrid)
deallocate(ycgrid)
deallocate(xsurf)
deallocate(ysurf)
deallocate(gsurf)
end program
The subroutines used:
!===========================================
subroutine write_two_columns (nnn,xxx,yyy,filename)
implicit none
integer i,nnn
real(8) xxx(nnn),yyy(nnn)
character(LEN=*) filename
open(unit=123,file=filename,action='write')
do i=1,nnn
write(123,*) xxx(i),yyy(i)
end do
close(123)
end subroutine
and the other subroutine:
!===========================================
subroutine write_three_columns (nnn,xxx,yyy,zzz,filename)
implicit none
integer i,nnn
real(8) xxx(nnn),yyy(nnn),zzz(nnn)
character(LEN=*) filename
open(unit=123,file=filename,action='write')
do i=1,nnn
write(123,*) xxx(i),yyy(i),zzz(i)
end do
close(123)
end subroutine
!===========================================
Shouldn't it be (rho(j)-rho1)? You fill rho(1:nel), but only use rho(1:7)!
By the way, be careful with your variable initialization... You assign reals to integers, and do mixed type arithmetics. Be careful with this as it might lead to unexpected results. Use your compiler to detect those issues.
I have a piece of experimental code that works perfectly with serial compilation and execution. When I compile it with openmp option on ifort (on ubuntu), the compilation goes on fine but the execution stops abruptly. The code is as follows:
!!!!!!!! module
module array
implicit none
real(kind=8),allocatable :: y(:)
end module array
module nonarray
implicit none
real(kind=8):: aa
end module nonarray
use nonarray; use array
implicit none
integer(kind=8):: iter,i
integer(kind=8),parameter:: id=1
real(kind=8),allocatable:: yt(:)
allocate(y(id)); allocate(yt(id)); y=0.d0; yt=0.d0
aa=4.d0 !!A SYSTEM PARAMETER
!$OMP PARALLEL PRIVATE(y,yt,iter,i)
!$OMP DO
loop1: do iter=1,20 !! THE INITIAL CONDITION LOOP
call random_number(y)!! RANDOM INITIALIZATION OF THE VARIABLE
loop2: do i=1,10000 !! ITERATION OF THE SYSTEM
call evolve(yt)
y=yt
enddo loop2 !! END OF SYSTEM ITERATION
write(1,*)aa,yt
enddo loop1 !!INITIAL CONDITION ITERATION DONE
!$OMP ENDDO
!$OMP END PARALLEL
stop
end
recursive subroutine evolve(yevl)
use nonarray; use array
implicit none
integer(kind=8),parameter:: id=1
real(kind=8):: xf
real(kind=8),intent(out):: yevl(id)
xf=aa*y(1)*(1.d0-y(1))
yevl(1)=xf
end subroutine evolve
For compilation I use the following command:
ifort -openmp -fpp test.f90.
test.f90 being the name of the program.
Any suggestions or help is highly appreciated.
I am not an OMP expert, but I think if the subroutine evolve should see a different (private) y in each thread, you should pass it directly from within the parallelized code block to the subroutine instead of importing it from an external module:
module common
use iso_fortran_env
implicit none
integer, parameter :: dp = real64
real(dp) :: aa
contains
subroutine evolve(y, yevl)
implicit none
real(dp), intent(in) :: y(:)
real(dp), intent(out):: yevl(:)
yevl(1) = aa * y(1) * (1.0_dp - y(1))
end subroutine evolve
end module common
program test
use common
implicit none
integer :: iter, i
real(dp), allocatable :: yt(:), y(:)
allocate(yt(1), y(1))
y(:) = 0.0_dp
yt(:) = 0.0_dp
aa = 4.0_dp
!$OMP PARALLEL DO PRIVATE(y,yt,iter,i)
loop1: do iter = 1, 20
call random_number(y)
loop2: do i = 1, 10000
call evolve(y, yt)
y = yt
end do loop2
write(*,*) aa, yt
end do loop1
!$OMP END PARALLEL DO
end program test
Just an additional warning: the code above worked with various compilers (nagfor 5.3.1, gfortran 4.6.3, ifort 13.0.1), but not with ifort 12.1.6. So, although I can't see any obvious problems with it, I may have messed up something.