Big integer factorial function in Fortran, as efficient as python or Haskell
3
Here's my factorial function in Fortran.
module facmod
implicit none
contains
function factorial (n) result (fac)
use FMZM
integer, intent(in) :: n
integer :: i
type(IM) :: fac
fac = 1
if(n==0) then
fac = 1
elseif(n==1) then
fac = 1
elseif(n==2) then
fac = 2
elseif(n < 0) then
write(*,*) 'Error in factorial N=', n
stop 1
else
do i = 1, n
fac = fac * i
enddo
endif
end function factorial
end module facmod
program main
use FMZM
use facmod, only: factorial
implicit none
type(IM) :: res
integer :: n, lenr
character (len=:), allocatable :: str
character(len=1024) :: fmat
print*,'enter the value of n'
read*, n
res = factorial(n)
lenr = log10(TO_FM(res))+2
allocate(character(len=lenr) :: str)
write (fmat, "(A5,I0)") "i", lenr
call im_form(fmat, res, str)
print*, trim( adjustl(str))
end program main
I compile using FMZM:
gfortran -std=f2008 fac.F90 fmlib.a -o fac
echo -e "1000" | .fac computes easy. However, if I give this echo -e "3600" | .fac, I already get an error on my machine:
Error in FM. More than 200000 type (FM), (ZM), (IM) numbers
have been defined. Variable SIZE_OF_START in file
FMSAVE.f95 defines this value.
Possible causes of this error and remedies:
(1) Make sure all subroutines (also functions that do not
return type FM, ZM, or IM function values) have
CALL FM_ENTER_USER_ROUTINE
at the start and
CALL FM_EXIT_USER_ROUTINE
at the end and before any other return, and all
functions returning an FM, ZM, or IM function value have
CALL FM_ENTER_USER_FUNCTION(F)
at the start and
CALL FM_EXIT_USER_FUNCTION(F)
at the end and before any other return, where the actual
function name replaces F above.
Otherwise that routine could be leaking memory, and
worse, could get wrong results because of deleting some
FM, ZM, or IM temporary variables too soon.
(2) Make sure all subroutines and functions declare any
local type FM, ZM, or IM variables as saved. Otherwise
some compilers create new instances of those variables
with each call, leaking memory.
For example:
SUBROUTINE SUB(A,B,C,X,Y,RESULT)
TYPE (FM) :: A,B,C,X,Y,RESULT,ERR,TOL,H
Here A,B,C,X,Y,RESULT are the input variables and
ERR,TOL,H are local variables. The fix is:
SUBROUTINE SUB(A,B,C,X,Y,RESULT)
TYPE (FM) :: A,B,C,X,Y,RESULT
TYPE (FM), SAVE :: ERR,TOL,H
(3) Since = assignments for multiple precision variables are
the trigger for cleaning up temporary multiple precision
variables, a loop with subroutine calls that has no =
assignments can run out of space to store temporaries.
For example:
DO J = 1, N
CALL SUB(A,B,C,TO_FM(0),TO_FM(1),RESULT)
ENDDO
Most compilers will create two temporary variables with
each call, to hold the TO_FM values.
One fix is to put an assignment into the loop:
DO J = 1, N
ZERO = TO_FM(0)
CALL SUB(A,B,C,ZERO,TO_FM(1),RESULT)
ENDDO
(4) If a routine uses allocatable type FM, ZM, or IM arrays
and allocates and deallocates with each call, then after
many calls this limit on number of variables could be
exceeded, since new FM variable index numbers are
generated for each call to the routine.
A fix for this is to call FM_DEALLOCATE before actually
deallocating each array, so those index numbers can be
re-used. For example:
DEALLOCATE(T)
becomes:
CALL FM_DEALLOCATE(T)
DEALLOCATE(T)
(5) If none of this helps, try running this program again
after increasing the value of SIZE_OF_START and
re-compiling.
What optimizations or Fortran idioms am I missing that is hurting my performance so much?
For example, in python, I can factorial numbers much larger than 3500:
>>> import math
>>> math.factorial(100000)
Or in Haskell:
Prelude> product [1..100000]
Both these compute, not exactly quickly, but without error.
How can I improve my algorithm or better use existing libraries to improve performance of large integer factorials in Fortran? Is there a more appropriate big integer library than FMZM?
fortran biginteger arbitrary-precision fmzm
asked Nov 24 '18 at 21:05
MittenchopsMittenchops
6,5052268139
add a comment |
3
Here's my factorial function in Fortran.
module facmod
implicit none
contains
function factorial (n) result (fac)
use FMZM
integer, intent(in) :: n
integer :: i
type(IM) :: fac
fac = 1
if(n==0) then
fac = 1
elseif(n==1) then
fac = 1
elseif(n==2) then
fac = 2
elseif(n < 0) then
write(*,*) 'Error in factorial N=', n
stop 1
else
do i = 1, n
fac = fac * i
enddo
endif
end function factorial
end module facmod
program main
use FMZM
use facmod, only: factorial
implicit none
type(IM) :: res
integer :: n, lenr
character (len=:), allocatable :: str
character(len=1024) :: fmat
print*,'enter the value of n'
read*, n
res = factorial(n)
lenr = log10(TO_FM(res))+2
allocate(character(len=lenr) :: str)
write (fmat, "(A5,I0)") "i", lenr
call im_form(fmat, res, str)
print*, trim( adjustl(str))
end program main
I compile using FMZM:
gfortran -std=f2008 fac.F90 fmlib.a -o fac
echo -e "1000" | .fac computes easy. However, if I give this echo -e "3600" | .fac, I already get an error on my machine:
Error in FM. More than 200000 type (FM), (ZM), (IM) numbers
have been defined. Variable SIZE_OF_START in file
FMSAVE.f95 defines this value.
Possible causes of this error and remedies:
(1) Make sure all subroutines (also functions that do not
return type FM, ZM, or IM function values) have
CALL FM_ENTER_USER_ROUTINE
at the start and
CALL FM_EXIT_USER_ROUTINE
at the end and before any other return, and all
functions returning an FM, ZM, or IM function value have
CALL FM_ENTER_USER_FUNCTION(F)
at the start and
CALL FM_EXIT_USER_FUNCTION(F)
at the end and before any other return, where the actual
function name replaces F above.
Otherwise that routine could be leaking memory, and
worse, could get wrong results because of deleting some
FM, ZM, or IM temporary variables too soon.
(2) Make sure all subroutines and functions declare any
local type FM, ZM, or IM variables as saved. Otherwise
some compilers create new instances of those variables
with each call, leaking memory.
For example:
SUBROUTINE SUB(A,B,C,X,Y,RESULT)
TYPE (FM) :: A,B,C,X,Y,RESULT,ERR,TOL,H
Here A,B,C,X,Y,RESULT are the input variables and
ERR,TOL,H are local variables. The fix is:
SUBROUTINE SUB(A,B,C,X,Y,RESULT)
TYPE (FM) :: A,B,C,X,Y,RESULT
TYPE (FM), SAVE :: ERR,TOL,H
(3) Since = assignments for multiple precision variables are
the trigger for cleaning up temporary multiple precision
variables, a loop with subroutine calls that has no =
assignments can run out of space to store temporaries.
For example:
DO J = 1, N
CALL SUB(A,B,C,TO_FM(0),TO_FM(1),RESULT)
ENDDO
Most compilers will create two temporary variables with
each call, to hold the TO_FM values.
One fix is to put an assignment into the loop:
DO J = 1, N
ZERO = TO_FM(0)
CALL SUB(A,B,C,ZERO,TO_FM(1),RESULT)
ENDDO
(4) If a routine uses allocatable type FM, ZM, or IM arrays
and allocates and deallocates with each call, then after
many calls this limit on number of variables could be
exceeded, since new FM variable index numbers are
generated for each call to the routine.
A fix for this is to call FM_DEALLOCATE before actually
deallocating each array, so those index numbers can be
re-used. For example:
DEALLOCATE(T)
becomes:
CALL FM_DEALLOCATE(T)
DEALLOCATE(T)
(5) If none of this helps, try running this program again
after increasing the value of SIZE_OF_START and
re-compiling.
What optimizations or Fortran idioms am I missing that is hurting my performance so much?
For example, in python, I can factorial numbers much larger than 3500:
>>> import math
>>> math.factorial(100000)
Or in Haskell:
Prelude> product [1..100000]
Both these compute, not exactly quickly, but without error.
How can I improve my algorithm or better use existing libraries to improve performance of large integer factorials in Fortran? Is there a more appropriate big integer library than FMZM?
fortran biginteger arbitrary-precision fmzm
asked Nov 24 '18 at 21:05
MittenchopsMittenchops
6,5052268139
Can't help without knowing what FMZM is or what type(fm) means.
– evets
Nov 24 '18 at 21:33
Thank you, @evets. It's a big integer library. I don't know that it's the best one or even recommended, but it's one I found recommended on stackoverflow here: stackoverflow.com/questions/38801846/… Documentation here: dmsmith.lmu.build
– Mittenchops
Nov 24 '18 at 21:42
Thanks, Rodrigo Rodrigues. As written, it uses a do loop and does not use recursion.
– Mittenchops
Nov 25 '18 at 7:36
Can I ask why you need such big factorials?
– Ian Bush
Nov 25 '18 at 10:49
add a comment |
3
3
3
Here's my factorial function in Fortran.
module facmod
implicit none
contains
function factorial (n) result (fac)
use FMZM
integer, intent(in) :: n
integer :: i
type(IM) :: fac
fac = 1
if(n==0) then
fac = 1
elseif(n==1) then
fac = 1
elseif(n==2) then
fac = 2
elseif(n < 0) then
write(*,*) 'Error in factorial N=', n
stop 1
else
do i = 1, n
fac = fac * i
enddo
endif
end function factorial
end module facmod
program main
use FMZM
use facmod, only: factorial
implicit none
type(IM) :: res
integer :: n, lenr
character (len=:), allocatable :: str
character(len=1024) :: fmat
print*,'enter the value of n'
read*, n
res = factorial(n)
lenr = log10(TO_FM(res))+2
allocate(character(len=lenr) :: str)
write (fmat, "(A5,I0)") "i", lenr
call im_form(fmat, res, str)
print*, trim( adjustl(str))
end program main
I compile using FMZM:
gfortran -std=f2008 fac.F90 fmlib.a -o fac
echo -e "1000" | .fac computes easy. However, if I give this echo -e "3600" | .fac, I already get an error on my machine:
Error in FM. More than 200000 type (FM), (ZM), (IM) numbers
have been defined. Variable SIZE_OF_START in file
FMSAVE.f95 defines this value.
Possible causes of this error and remedies:
(1) Make sure all subroutines (also functions that do not
return type FM, ZM, or IM function values) have
CALL FM_ENTER_USER_ROUTINE
at the start and
CALL FM_EXIT_USER_ROUTINE
at the end and before any other return, and all
functions returning an FM, ZM, or IM function value have
CALL FM_ENTER_USER_FUNCTION(F)
at the start and
CALL FM_EXIT_USER_FUNCTION(F)
at the end and before any other return, where the actual
function name replaces F above.
Otherwise that routine could be leaking memory, and
worse, could get wrong results because of deleting some
FM, ZM, or IM temporary variables too soon.
(2) Make sure all subroutines and functions declare any
local type FM, ZM, or IM variables as saved. Otherwise
some compilers create new instances of those variables
with each call, leaking memory.
For example:
SUBROUTINE SUB(A,B,C,X,Y,RESULT)
TYPE (FM) :: A,B,C,X,Y,RESULT,ERR,TOL,H
Here A,B,C,X,Y,RESULT are the input variables and
ERR,TOL,H are local variables. The fix is:
SUBROUTINE SUB(A,B,C,X,Y,RESULT)
TYPE (FM) :: A,B,C,X,Y,RESULT
TYPE (FM), SAVE :: ERR,TOL,H
(3) Since = assignments for multiple precision variables are
the trigger for cleaning up temporary multiple precision
variables, a loop with subroutine calls that has no =
assignments can run out of space to store temporaries.
For example:
DO J = 1, N
CALL SUB(A,B,C,TO_FM(0),TO_FM(1),RESULT)
ENDDO
Most compilers will create two temporary variables with
each call, to hold the TO_FM values.
One fix is to put an assignment into the loop:
DO J = 1, N
ZERO = TO_FM(0)
CALL SUB(A,B,C,ZERO,TO_FM(1),RESULT)
ENDDO
(4) If a routine uses allocatable type FM, ZM, or IM arrays
and allocates and deallocates with each call, then after
many calls this limit on number of variables could be
exceeded, since new FM variable index numbers are
generated for each call to the routine.
A fix for this is to call FM_DEALLOCATE before actually
deallocating each array, so those index numbers can be
re-used. For example:
DEALLOCATE(T)
becomes:
CALL FM_DEALLOCATE(T)
DEALLOCATE(T)
(5) If none of this helps, try running this program again
after increasing the value of SIZE_OF_START and
re-compiling.
What optimizations or Fortran idioms am I missing that is hurting my performance so much?
For example, in python, I can factorial numbers much larger than 3500:
>>> import math
>>> math.factorial(100000)
Or in Haskell:
Prelude> product [1..100000]
Both these compute, not exactly quickly, but without error.
How can I improve my algorithm or better use existing libraries to improve performance of large integer factorials in Fortran? Is there a more appropriate big integer library than FMZM?
fortran biginteger arbitrary-precision fmzm
asked Nov 24 '18 at 21:05
MittenchopsMittenchops
6,5052268139
Here's my factorial function in Fortran.
module facmod
implicit none
contains
function factorial (n) result (fac)
use FMZM
integer, intent(in) :: n
integer :: i
type(IM) :: fac
fac = 1
if(n==0) then
fac = 1
elseif(n==1) then
fac = 1
elseif(n==2) then
fac = 2
elseif(n < 0) then
write(*,*) 'Error in factorial N=', n
stop 1
else
do i = 1, n
fac = fac * i
enddo
endif
end function factorial
end module facmod
program main
use FMZM
use facmod, only: factorial
implicit none
type(IM) :: res
integer :: n, lenr
character (len=:), allocatable :: str
character(len=1024) :: fmat
print*,'enter the value of n'
read*, n
res = factorial(n)
lenr = log10(TO_FM(res))+2
allocate(character(len=lenr) :: str)
write (fmat, "(A5,I0)") "i", lenr
call im_form(fmat, res, str)
print*, trim( adjustl(str))
end program main
I compile using FMZM:
gfortran -std=f2008 fac.F90 fmlib.a -o fac
echo -e "1000" | .fac computes easy. However, if I give this echo -e "3600" | .fac, I already get an error on my machine:
Error in FM. More than 200000 type (FM), (ZM), (IM) numbers
have been defined. Variable SIZE_OF_START in file
FMSAVE.f95 defines this value.
Possible causes of this error and remedies:
(1) Make sure all subroutines (also functions that do not
return type FM, ZM, or IM function values) have
CALL FM_ENTER_USER_ROUTINE
at the start and
CALL FM_EXIT_USER_ROUTINE
at the end and before any other return, and all
functions returning an FM, ZM, or IM function value have
CALL FM_ENTER_USER_FUNCTION(F)
at the start and
CALL FM_EXIT_USER_FUNCTION(F)
at the end and before any other return, where the actual
function name replaces F above.
Otherwise that routine could be leaking memory, and
worse, could get wrong results because of deleting some
FM, ZM, or IM temporary variables too soon.
(2) Make sure all subroutines and functions declare any
local type FM, ZM, or IM variables as saved. Otherwise
some compilers create new instances of those variables
with each call, leaking memory.
For example:
SUBROUTINE SUB(A,B,C,X,Y,RESULT)
TYPE (FM) :: A,B,C,X,Y,RESULT,ERR,TOL,H
Here A,B,C,X,Y,RESULT are the input variables and
ERR,TOL,H are local variables. The fix is:
SUBROUTINE SUB(A,B,C,X,Y,RESULT)
TYPE (FM) :: A,B,C,X,Y,RESULT
TYPE (FM), SAVE :: ERR,TOL,H
(3) Since = assignments for multiple precision variables are
the trigger for cleaning up temporary multiple precision
variables, a loop with subroutine calls that has no =
assignments can run out of space to store temporaries.
For example:
DO J = 1, N
CALL SUB(A,B,C,TO_FM(0),TO_FM(1),RESULT)
ENDDO
Most compilers will create two temporary variables with
each call, to hold the TO_FM values.
One fix is to put an assignment into the loop:
DO J = 1, N
ZERO = TO_FM(0)
CALL SUB(A,B,C,ZERO,TO_FM(1),RESULT)
ENDDO
(4) If a routine uses allocatable type FM, ZM, or IM arrays
and allocates and deallocates with each call, then after
many calls this limit on number of variables could be
exceeded, since new FM variable index numbers are
generated for each call to the routine.
A fix for this is to call FM_DEALLOCATE before actually
deallocating each array, so those index numbers can be
re-used. For example:
DEALLOCATE(T)
becomes:
CALL FM_DEALLOCATE(T)
DEALLOCATE(T)
(5) If none of this helps, try running this program again
after increasing the value of SIZE_OF_START and
re-compiling.
What optimizations or Fortran idioms am I missing that is hurting my performance so much?
For example, in python, I can factorial numbers much larger than 3500:
>>> import math
>>> math.factorial(100000)
Or in Haskell:
Prelude> product [1..100000]
Both these compute, not exactly quickly, but without error.
How can I improve my algorithm or better use existing libraries to improve performance of large integer factorials in Fortran? Is there a more appropriate big integer library than FMZM?
fortran biginteger arbitrary-precision fmzm
fortran biginteger arbitrary-precision fmzm
asked Nov 24 '18 at 21:05
MittenchopsMittenchops
6,5052268139
asked Nov 24 '18 at 21:05
MittenchopsMittenchops
6,5052268139
edited Nov 24 '18 at 21:19
Mittenchops
asked Nov 24 '18 at 21:05
MittenchopsMittenchops
6,5052268139
asked Nov 24 '18 at 21:05
MittenchopsMittenchops
6,5052268139
asked Nov 24 '18 at 21:05
MittenchopsMittenchops
6,5052268139
6,5052268139
Can't help without knowing what FMZM is or what type(fm) means.
– evets
Nov 24 '18 at 21:33
Thank you, @evets. It's a big integer library. I don't know that it's the best one or even recommended, but it's one I found recommended on stackoverflow here: stackoverflow.com/questions/38801846/… Documentation here: dmsmith.lmu.build
– Mittenchops
Nov 24 '18 at 21:42
Thanks, Rodrigo Rodrigues. As written, it uses a do loop and does not use recursion.
– Mittenchops
Nov 25 '18 at 7:36
Can I ask why you need such big factorials?
– Ian Bush
Nov 25 '18 at 10:49
add a comment |
Can't help without knowing what FMZM is or what type(fm) means.
– evets
Nov 24 '18 at 21:33
Thank you, @evets. It's a big integer library. I don't know that it's the best one or even recommended, but it's one I found recommended on stackoverflow here: stackoverflow.com/questions/38801846/… Documentation here: dmsmith.lmu.build
– Mittenchops
Nov 24 '18 at 21:42
Thanks, Rodrigo Rodrigues. As written, it uses a do loop and does not use recursion.
– Mittenchops
Nov 25 '18 at 7:36
Can I ask why you need such big factorials?
– Ian Bush
Nov 25 '18 at 10:49
Can't help without knowing what FMZM is or what type(fm) means.
– evets
Nov 24 '18 at 21:33
Can't help without knowing what FMZM is or what type(fm) means.
– evets
Nov 24 '18 at 21:33
Thank you, @evets. It's a big integer library. I don't know that it's the best one or even recommended, but it's one I found recommended on stackoverflow here: stackoverflow.com/questions/38801846/… Documentation here: dmsmith.lmu.build
– Mittenchops
Nov 24 '18 at 21:42
Thank you, @evets. It's a big integer library. I don't know that it's the best one or even recommended, but it's one I found recommended on stackoverflow here: stackoverflow.com/questions/38801846/… Documentation here: dmsmith.lmu.build
– Mittenchops
Nov 24 '18 at 21:42
Thanks, Rodrigo Rodrigues. As written, it uses a do loop and does not use recursion.
– Mittenchops
Nov 25 '18 at 7:36
Thanks, Rodrigo Rodrigues. As written, it uses a do loop and does not use recursion.
– Mittenchops
Nov 25 '18 at 7:36
Can I ask why you need such big factorials?
– Ian Bush
Nov 25 '18 at 10:49
Can I ask why you need such big factorials?
– Ian Bush
Nov 25 '18 at 10:49
add a comment |
1 Answer
1
active
oldest
votes
3
Try this. Apart from minor cosmetic changes, I just followed the recommendations of the error message in your question:
- added calls to FM_ENTER_USER_FUNCTION and FM_EXIT_USER_FUNCTION,
- added an assignment inside the loop (without this
ii = to_im(i), it still fails, but I'm not sure why, as there is already an assignment withfac = fac * i, and accordind to the doc the assignment triggers cleaning up temporaries), - renamed
factorialin main program as there is already a function with this name in FMZM.
Tested with ifort and n=100000.
module fac_mod
implicit none
contains
function factorial(n) result(fac)
use FMZM
integer, intent(in) :: n
integer :: i
type(IM) :: fac
type(IM), save :: ii
call FM_ENTER_USER_FUNCTION(fac)
fac = to_im(1)
if (n < 0) then
write (*, *) "Error in factorial N=", n
stop 1
else if (n > 1) then
do i = 1, n
ii = to_im(i)
fac = fac * ii
end do
end if
call FM_EXIT_USER_FUNCTION(fac)
end function factorial
end module fac_mod
program main
use FMZM
use fac_mod, only: f=>factorial
implicit none
type(IM) :: res
integer :: n, lenr
character(:), allocatable :: str
character(1024) :: fmat
print *, "enter the value of n"
read *, n
res = f(n)
lenr = 2 + log10(TO_FM(res))
allocate (character(lenr) :: str)
write (fmat, "(A5,I0)") "i", lenr
call im_form(fmat, res, str)
print *, trim(adjustl(str))
end program main
answered Nov 25 '18 at 12:18
Jean-Claude ArbautJean-Claude Arbaut
40518
Thank you, @Jean-Claude Arbaut. Your other observation, that there is already a factorial function in FMZM, also helped. I realized that my function was probably picking up on that, and it faced this limitation. Your version is better than the built-in as well, it looks like! Thank you!
– Mittenchops
Nov 25 '18 at 17:50
add a comment |
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1 Answer
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Try this. Apart from minor cosmetic changes, I just followed the recommendations of the error message in your question:
- added calls to FM_ENTER_USER_FUNCTION and FM_EXIT_USER_FUNCTION,
- added an assignment inside the loop (without this
ii = to_im(i), it still fails, but I'm not sure why, as there is already an assignment withfac = fac * i, and accordind to the doc the assignment triggers cleaning up temporaries), - renamed
factorialin main program as there is already a function with this name in FMZM.
Tested with ifort and n=100000.
module fac_mod
implicit none
contains
function factorial(n) result(fac)
use FMZM
integer, intent(in) :: n
integer :: i
type(IM) :: fac
type(IM), save :: ii
call FM_ENTER_USER_FUNCTION(fac)
fac = to_im(1)
if (n < 0) then
write (*, *) "Error in factorial N=", n
stop 1
else if (n > 1) then
do i = 1, n
ii = to_im(i)
fac = fac * ii
end do
end if
call FM_EXIT_USER_FUNCTION(fac)
end function factorial
end module fac_mod
program main
use FMZM
use fac_mod, only: f=>factorial
implicit none
type(IM) :: res
integer :: n, lenr
character(:), allocatable :: str
character(1024) :: fmat
print *, "enter the value of n"
read *, n
res = f(n)
lenr = 2 + log10(TO_FM(res))
allocate (character(lenr) :: str)
write (fmat, "(A5,I0)") "i", lenr
call im_form(fmat, res, str)
print *, trim(adjustl(str))
end program main
answered Nov 25 '18 at 12:18
Jean-Claude ArbautJean-Claude Arbaut
40518
Thank you, @Jean-Claude Arbaut. Your other observation, that there is already a factorial function in FMZM, also helped. I realized that my function was probably picking up on that, and it faced this limitation. Your version is better than the built-in as well, it looks like! Thank you!
– Mittenchops
Nov 25 '18 at 17:50
add a comment |
3
Try this. Apart from minor cosmetic changes, I just followed the recommendations of the error message in your question:
- added calls to FM_ENTER_USER_FUNCTION and FM_EXIT_USER_FUNCTION,
- added an assignment inside the loop (without this
ii = to_im(i), it still fails, but I'm not sure why, as there is already an assignment withfac = fac * i, and accordind to the doc the assignment triggers cleaning up temporaries), - renamed
factorialin main program as there is already a function with this name in FMZM.
Tested with ifort and n=100000.
module fac_mod
implicit none
contains
function factorial(n) result(fac)
use FMZM
integer, intent(in) :: n
integer :: i
type(IM) :: fac
type(IM), save :: ii
call FM_ENTER_USER_FUNCTION(fac)
fac = to_im(1)
if (n < 0) then
write (*, *) "Error in factorial N=", n
stop 1
else if (n > 1) then
do i = 1, n
ii = to_im(i)
fac = fac * ii
end do
end if
call FM_EXIT_USER_FUNCTION(fac)
end function factorial
end module fac_mod
program main
use FMZM
use fac_mod, only: f=>factorial
implicit none
type(IM) :: res
integer :: n, lenr
character(:), allocatable :: str
character(1024) :: fmat
print *, "enter the value of n"
read *, n
res = f(n)
lenr = 2 + log10(TO_FM(res))
allocate (character(lenr) :: str)
write (fmat, "(A5,I0)") "i", lenr
call im_form(fmat, res, str)
print *, trim(adjustl(str))
end program main
answered Nov 25 '18 at 12:18
Jean-Claude ArbautJean-Claude Arbaut
40518
Thank you, @Jean-Claude Arbaut. Your other observation, that there is already a factorial function in FMZM, also helped. I realized that my function was probably picking up on that, and it faced this limitation. Your version is better than the built-in as well, it looks like! Thank you!
– Mittenchops
Nov 25 '18 at 17:50
add a comment |
3
3
3
Try this. Apart from minor cosmetic changes, I just followed the recommendations of the error message in your question:
- added calls to FM_ENTER_USER_FUNCTION and FM_EXIT_USER_FUNCTION,
- added an assignment inside the loop (without this
ii = to_im(i), it still fails, but I'm not sure why, as there is already an assignment withfac = fac * i, and accordind to the doc the assignment triggers cleaning up temporaries), - renamed
factorialin main program as there is already a function with this name in FMZM.
Tested with ifort and n=100000.
module fac_mod
implicit none
contains
function factorial(n) result(fac)
use FMZM
integer, intent(in) :: n
integer :: i
type(IM) :: fac
type(IM), save :: ii
call FM_ENTER_USER_FUNCTION(fac)
fac = to_im(1)
if (n < 0) then
write (*, *) "Error in factorial N=", n
stop 1
else if (n > 1) then
do i = 1, n
ii = to_im(i)
fac = fac * ii
end do
end if
call FM_EXIT_USER_FUNCTION(fac)
end function factorial
end module fac_mod
program main
use FMZM
use fac_mod, only: f=>factorial
implicit none
type(IM) :: res
integer :: n, lenr
character(:), allocatable :: str
character(1024) :: fmat
print *, "enter the value of n"
read *, n
res = f(n)
lenr = 2 + log10(TO_FM(res))
allocate (character(lenr) :: str)
write (fmat, "(A5,I0)") "i", lenr
call im_form(fmat, res, str)
print *, trim(adjustl(str))
end program main
answered Nov 25 '18 at 12:18
Jean-Claude ArbautJean-Claude Arbaut
40518
Try this. Apart from minor cosmetic changes, I just followed the recommendations of the error message in your question:
- added calls to FM_ENTER_USER_FUNCTION and FM_EXIT_USER_FUNCTION,
- added an assignment inside the loop (without this
ii = to_im(i), it still fails, but I'm not sure why, as there is already an assignment withfac = fac * i, and accordind to the doc the assignment triggers cleaning up temporaries), - renamed
factorialin main program as there is already a function with this name in FMZM.
Tested with ifort and n=100000.
module fac_mod
implicit none
contains
function factorial(n) result(fac)
use FMZM
integer, intent(in) :: n
integer :: i
type(IM) :: fac
type(IM), save :: ii
call FM_ENTER_USER_FUNCTION(fac)
fac = to_im(1)
if (n < 0) then
write (*, *) "Error in factorial N=", n
stop 1
else if (n > 1) then
do i = 1, n
ii = to_im(i)
fac = fac * ii
end do
end if
call FM_EXIT_USER_FUNCTION(fac)
end function factorial
end module fac_mod
program main
use FMZM
use fac_mod, only: f=>factorial
implicit none
type(IM) :: res
integer :: n, lenr
character(:), allocatable :: str
character(1024) :: fmat
print *, "enter the value of n"
read *, n
res = f(n)
lenr = 2 + log10(TO_FM(res))
allocate (character(lenr) :: str)
write (fmat, "(A5,I0)") "i", lenr
call im_form(fmat, res, str)
print *, trim(adjustl(str))
end program main
answered Nov 25 '18 at 12:18
Jean-Claude ArbautJean-Claude Arbaut
40518
answered Nov 25 '18 at 12:18
Jean-Claude ArbautJean-Claude Arbaut
40518
answered Nov 25 '18 at 12:18
Jean-Claude ArbautJean-Claude Arbaut
40518
answered Nov 25 '18 at 12:18
Jean-Claude ArbautJean-Claude Arbaut
40518
40518
Thank you, @Jean-Claude Arbaut. Your other observation, that there is already a factorial function in FMZM, also helped. I realized that my function was probably picking up on that, and it faced this limitation. Your version is better than the built-in as well, it looks like! Thank you!
– Mittenchops
Nov 25 '18 at 17:50
add a comment |
Thank you, @Jean-Claude Arbaut. Your other observation, that there is already a factorial function in FMZM, also helped. I realized that my function was probably picking up on that, and it faced this limitation. Your version is better than the built-in as well, it looks like! Thank you!
– Mittenchops
Nov 25 '18 at 17:50
Thank you, @Jean-Claude Arbaut. Your other observation, that there is already a factorial function in FMZM, also helped. I realized that my function was probably picking up on that, and it faced this limitation. Your version is better than the built-in as well, it looks like! Thank you!
– Mittenchops
Nov 25 '18 at 17:50
Thank you, @Jean-Claude Arbaut. Your other observation, that there is already a factorial function in FMZM, also helped. I realized that my function was probably picking up on that, and it faced this limitation. Your version is better than the built-in as well, it looks like! Thank you!
– Mittenchops
Nov 25 '18 at 17:50
add a comment |
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Can't help without knowing what FMZM is or what type(fm) means.
– evets
Nov 24 '18 at 21:33
Thank you, @evets. It's a big integer library. I don't know that it's the best one or even recommended, but it's one I found recommended on stackoverflow here: stackoverflow.com/questions/38801846/… Documentation here: dmsmith.lmu.build
– Mittenchops
Nov 24 '18 at 21:42
Thanks, Rodrigo Rodrigues. As written, it uses a do loop and does not use recursion.
– Mittenchops
Nov 25 '18 at 7:36
Can I ask why you need such big factorials?
– Ian Bush
Nov 25 '18 at 10:49