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[?] Break a time consuming integration into pieces?

Posted 8 years ago

I am trying to calculate an expression which has the following form

Sum[(-1)^(n+1) Bionomial[4,n] NIntegrate[S[n,x] Q[n,x] V[n,x] F[x], {x,0,2000} , WorkingPercision -> 5 ] , {n, 4} ]

Where we have :

G[x_ ] := 2 Pi x p[x] Exp[-2 Pi Integrate[t p[t], {t, 0, x}]]

p[x_ ] := Piecewise[ {{0 , x > 140}} , Exp[ -0.0071* x] ];

S[n_ ,x_ ] := Exp[ -n x];

Q[n_ ,x_ ] := Product[ Exp[-2 Pi Integrate [1 - 1/(n x)^4 p[t] t ,  {t,x, Infinity }]] ,{n,4} ]

V[n_ ,x_ ] := Product[ Exp[-2 Pi Integrate [1 - 1/(n x / t^2 )^4 (1-p[t]) t ,  {t, x^2 , Infinity }]] ,{n,4} ]

F[x_ ] := G[x] Exp[Integrate[ -2 Pi (1- p[t]) t , {t, 0 , x }]]

Unfortunately the evaluation takes so much time. Is there any way to break this expression into pieces and perform calculation separately ? p.s. I also tried limiting WorkingPercision and MaxRecursion but it didn't work.

The acceptable WorkingPercision is 5 and the acceptable evaluation time is less than half an hour !

I appreciate your suggestions.

POSTED BY: Shahrooz Aghili
4 Replies
POSTED BY: Neil Singer
Posted 8 years ago
POSTED BY: Bill Simpson
POSTED BY: Shahrooz Aghili
Posted 8 years ago
POSTED BY: Bill Simpson
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