Re: calculating total emissions

Hi Dennis and Marry,
    Thank you very much for the help. I got it to work and it is much
faster.
    Lei

On Tue, Dec 15, 2009 at 11:01 PM, Mary Haley <haley@ucar.edu> wrote:

> [I meant to send this earlier, but got side-tracked. Some of what I say
> below echoes Dennis' comments.]
>
> Hi Lei,
>
> Do loops in any scripted language can be slow, and especially nested do
> loops.
>
> Since you can do array arithmetic in NCL without having to loop, I highly
> recommend using this feature. Also,, anything inside a do loop that doesn't
> need to be there should be moved outside the loop.
>
> Here's another UNTESTED version of your code, that's a bit shorter. This is
> probably not quite right, but hopefully you get the idea:
>
> alat2d = conform((/natime,nalat/),alat,1)
> rlat2 = (alat2d+1.429)*3.14159265/180.0 ; convert degree to radians
> rlat1 = (alat2d-1.429)*3.14159265/180.0
> temp = sin(rlat2)-sin(rlat1)
>
> diff_lon = 2.8152d*3.14159265d/180.0d
> R = 6371.0d*1000.0d ; unit is meterncd
> area = R*R*diff_lon*temp
> area = where(area.lt.0,0.0,area)
>
> totalfch4 =0.0d
>
> do i =0, natime-1
> do j=0,nalat-1
> kk = ind(.not.ismissing(aFCH4(i,j,:)))
> if(.not.all(ismissing(kk))) then
> totalfch4=sum(aFCH4(i,j,kk)*area)
>
> afch4(i) = afch4(i)+totalfch4
> end if
> delete(kk)
> end do
> end do
>
>
>
> On Dec 15, 2009, at 1:34 PM, Lei Meng wrote:
>
> Hi,
>> I was wondering if there are some faster ways to calculate globally
>> total emissions. I used the following code and it looped over each grid cell
>> to calculate total values. It takes so long to finish the calculation.
>> --------------------------
>> totalfch4=0.0d
>> do i =0, natime-1
>> do j=0,nalat-1
>> rlat2= (alat(j)+1.429)*3.14159265/180.0 ; convert degree to
>> radians
>> rlat1= (alat(j)-1.429)*3.14159265/180.0
>> temp1 = sin(rlat2)
>> temp2 = sin(rlat1)
>> temp = temp1-temp2
>>
>> do k=0,nalon-1
>> if(.not.ismissing(aFCH4(i,j,k))) then
>> diff_lon = 2.8152d*3.14159265d/180.0d
>> R=6371.0d*1000.0d ; unit is meterncd
>> area=R*R*diff_lon*temp
>> if(area.lt.0) then
>> area=0.0
>> end if
>> totalfch4=aFCH4(i,j,k)*area ; convert from
>> kgC/m2/s to kgC/s by multiplying area
>> afch4(i) = afch4(i)+totalfch4
>> end if
>> end do
>> end do
>> end do
>> ------------------------------------
>> Any suggestions would be appreciated. Thanks,
>> Lei
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>
>
Received on Wed Dec 16 06:47:13 2009