In GAMS models I often see loops where they are not really needed. E.g.
loop(i,
loop(j,
loop(k,
q(i,j,k) = 1;
)));
can be written as:
q(i,j,k) = 1;
Consider the larger fragment:
set i /i1*i200/;
alias(i,j,k);
parameter p(i,j,k);
p(i,j,k) = 1;
parameter q(i,j,k);
loop(i,
loop(j,
loop(k,
q(i,j,k) = 1;
)));
parameter q2(i,j,k);
loop((i,j,k),
q2(i,j,k) = 1;
);
The timing for the direct assignment to p(i,j,k) is 0.78 seconds. The time to populate q(i,j,k) is 18 seconds. The slightly different loop to fill q2 takes the same time: also 18 seconds. The difference is merely syntax. So if possible try not to use loops: not only is the code more compact, but it also performs better.
A more dramatic example is here (with card(i)=card(j)=card(k)=50):
| p(i,j,k) = max(0,p(i,j,k)); | 0.031 secs |
| loop((i,j,k), if(p(i,j,k)<0, p(i,j,k)=0); ); | 36.4 secs |
can you speed up this code?
ReplyDeletei must finish so many codes till monday. please can u help me?
*option limrow=100;
Set i nodes /n1*n40/;
Alias (i,j);
Scalar
EAmp /100e-6/
EElec /50e-3/
Prx
radius Radius of System /112.8338/
energy /100/
;
Parameters
y(i) y coordinate of node-i
x(i) x coordinate of node-i
s(i) data generated at node-i
d(i,j) distance between node-i and node-j
Ptx(i,j) consumed energy for transmission of data from node-i to node-j
random_radius radius
angle angle
M big number
Lin Max In Flow
Lout Max Out Flow
l
tekrar
;
Variables
t time
Positive Variables
f(i,j);
Binary Variable
a(i,j)
;
Equations
noFlow(i,j) no flow
flowBalance(i) flow balance
energyConstraint(i) energy constraint
binaryConstraint(i,j)
inConstraint(i)
outConstraint(i);
noFlow(i,j)$(ord(i)=ord(j) or ord(i)=1).. f(i,j) =e= 0;
flowBalance(i)$(ord(i)>1).. -sum(j,f(i,j)) + sum(j,f(j,i)) + t*s(i) =e= 0;
energyConstraint(i)$(ord(i)>1).. Prx*(sum(j$(ord(j)>1),f(j,i)))+sum(j,(Ptx(i,j)*f(i,j)))=l=energy;
binaryConstraint(i,j)$(ord(i)>1).. f(i,j) =l= M*a(i,j);
inConstraint(i)$(ord(i)>1).. sum(j$(ord(j)>1),a(j,i))=l=Lin;
outConstraint(i)$(ord(i)>1).. sum(j,a(i,j))=l=Lout;
file Sonuc /Sonuc.txt/;
file Coordinate /Coordinate.txt/;
file Flow /Flow.txt/;
option iterlim=10000000;
option reslim=10000000;
option optcr=0.001;
Model minimumBattery /All/;
for (tekrar=1 to 100 by 1,
for(l=2 to card(i),
angle=360*uniform(0,1);
random_radius= radius*sqrt(uniform(0,1));
x(i)$(ord(i)=l) = random_radius * cos(angle);
y(i)$(ord(i)=l) = random_radius * sin(angle);
);
x('n1')=0;
y('n1')=0;
d(i,j) = sqrt((sqr(x(i)-x(j))+sqr(y(i)-y(j))));
Ptx(i,j)$(ord(i)<> ord(j) and ord(i)<>1) = EElec + EAmp*sqr(d(i,j));
Prx = EElec;
s(i)$(ord(i)>1)=1000;
M=100000;
Lin=1;
Lout=1;
Solve minimumBattery using mip maximizing t;
*------------------------------------------------
option x :0:0:1; display x;
option y :0:0:1; display y;
* the set element labels are identified using their set identifier and the suffix (.tl)
put Coordinate;
loop(i,
put i.tl:4:0 x(i):12:0 y(i):12:0/;
);
* Bir degiskening degerini yazdirmak icin (.l) kullaniyoruz
*----Sonucu "LinearTopology_SingleTopology_Sonuc.txt" dosyasina yaz ---
put Sonuc;
put 'Lifetime' tekrar t.l:12:8 /;
$ontext
loop(i,
loop(j,
put$(f.l(i,j)>0) i.tl:4:0 j.tl:4:0 f.l(i,j):12:3 /;
);
);
$offtext
put Flow;
loop(i,
loop(j,
put$(f.l(i,j)>0) i.tl:4:0 j.tl:4:0 f.l(i,j):12:3 /;
);
);
);
I suggest to discuss this with your teacher.
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