請教大家，我在做一個一維擴散的模擬，
在我一步一步debug之後，知道問題在迴圈的部分，好像會無法結束??
可以成功編譯成執行檔，但一旦開始執行，就無法結束了，也無法輸出結果..
以下是程式碼，麻煩版有幫我看看哪邊出錯了??
program diffusion 　　!1-D diffusion
implicit none
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!宣告區
real L,D,J,C,T,F,smallt
!L=length,D=diffusivity,J=diffusion flux,C=initial concentration
!F=Fourier's number, smallt=time interval
real, parameter :: defaultL = 10
real, parameter :: defaultD = 1.03
real, parameter :: defaultJ = 1E-5
real, parameter :: defaultC = 1E-4
real array1(-1:10001),array2(-1:10001)
!the length is divided into 10000 pieces, 10001 nodes, 2 virtual nodes
integer*8 p, pmax, x
!p=pace, x=location
character mode
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!輸入設定參數
write(*,*) "press ""1"" to select the default values, or""2"" to input
them"
read(*,*) mode
if(mode=="1") then
L = defaultL
D = defaultD
J = defaultJ
C = defaultC
else
write(*,*) "please input the length:"
read(*,*)L
write(*,*) "please input the diffusivity:"
read(*,*)D
write(*,*) "please input the diffusion flux:"
read(*,*)J
write(*,*) "please input the initial concentration:"
read(*,*)C
end if
write(*,*) "please input the time:"
read(*,*)T
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!計算用到的參數
smallt = 0.25*L*L/D/10**8
pmax = T/smallt
F = D*smallt/(L*L)*10**8
array1 = C
array2 = C
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!這裡就是出錯的開始!!!
do p=1,pmax
do x=0,10000
array1(-1) = J*L/10000/D + array1(0)
array1(10001) = array1(10000) + array1(0) - array1(-1)
array2(x)=F*(array1(x+1)+array1(x-1))+(1-2*F)*array1(x)
end do
array1 = array2
end do
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!將陣列輸出到文字檔
open(unit=10,file="diffusion1.txt")
do x=-1,10001
write(10,*) array1(x)
end do
STOP
END

應該不是無法結束，是迴圈太大，pmax還要乘上10000

smallt = 0.25*L*L/D/10**8 檢查你的smallt的值如果沒有意外應該是0,導致pmax極大,迴圈跑不完改成smallt = 0.25*L*L/D/10.0**8.0 試試看不僅是這個地方,例如array1(-1) = J*L/10000/D這都會'讓你的結果與預期的不同

t=10,pamx=41200000,x=412000000000,粉大的迴圈,如果參數沒錯,也只能丟著給它跑啦

你可以再把迴圈裡跟x無關的拿出來，可能可以快一咪咪

呵三樓的精簡化本人常幹,不過它這個程式很簡單,只有兩行多餘差別不大啦.重點在t要多大,t=0.0001夠嗎?t=1,十分鐘跑完,I7 2600套裝很便宜電腦,更好的電腦得會更快這樣很快了,我的程式都要跑一周以上,有三週還沒跑完的

建議把你所計算的數值的order提高一點，電腦在進行計算的時候，其精度會有差別...