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mirror of https://github.com/pfloos/quack synced 2024-12-23 04:43:42 +01:00
This commit is contained in:
Pierre-Francois Loos 2020-10-14 08:41:01 +02:00
parent a65817ce3f
commit 60c55aa94a
2 changed files with 69 additions and 0 deletions

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* define $QUACK_ROOT
* blas
* lapack
* ninja
* gfortran
* python3
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* opam
* cmake
* wget
* automake

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src/utils/dfac.f90 Normal file
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double precision function dfac(n)
implicit none
integer :: n
double precision, external :: fact
dfac = fact(n)
end
!-------------------
! The following functions were taken with from Quantum Package
! (https://github.com/QuantumPackage/qp2 , AGPL license)
double precision function fact(n)
implicit none
integer :: n
double precision, save :: memo(1:100)
integer, save :: memomax = 1
integer :: i
double precision :: logfact
if (n<=memomax) then
if (n<2) then
fact = 1.d0
else
fact = memo(n)
endif
return
endif
memo(1) = 1.d0
do i=memomax+1,min(n,100)
memo(i) = memo(i-1)*dble(i)
enddo
memomax = min(n,100)
fact = dexp(logfact(n))
end function
double precision function logfact(n)
implicit none
integer :: n
double precision, save :: memo(1:100)
integer, save :: memomax = 1
integer :: i
if (n<=memomax) then
if (n<2) then
logfact = 0.d0
else
logfact = memo(n)
endif
return
endif
memo(1) = 0.d0
do i=memomax+1,min(n,100)
memo(i) = memo(i-1)+dlog(dble(i))
enddo
memomax = min(n,100)
logfact = memo(memomax)
do i=101,n
logfact = logfact + dlog(dble(i))
enddo
end function