# Alternative way for nested for loops and if statements

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cglr on 3 Dec 2019
Commented: cglr on 4 Dec 2019
Hi everyone,
I am looking an alternative way for the algorithm that is mentioned below. There are nested for loops and multiple if statements.
I would like to run it faster, do you have any opinion how to do that ?
for i = 1: totalCount
for j= 1: totalCount2
if (telArray(i,1) ~= telArray(j,1))
firstTel = find ( telArray(i,1) == sortedArray(:,3) ,1 );
[r] = find(heuristic(:,firstTel)~= 0);
placeOfFirst = r(1,1);
secondTel = find ( telArray(j,1) == sortedArray(:,3) ,1 );
[r] = find(heuristic(:,secondTel )~= 0);
placeOfSecond = r(1,1);
idx = placeOfFirst:repRate:macroPeriod;
sum1= sum(basePeriod(idx,2));
idx = placeOfSecond:repRate:macroPeriod;
sum2= sum(basePeriod(idx,2));
if( ( sum1> sum2+ 10 ) && (sortedArray (firstTel,1) > (sortedArray (secondTel , 1) + 1) ) )
firstDifference = sum1- sum2
sum1= sum1 + (macroPeriod / repRate) * ( sortedArray (secondTel ,1) - sortedArray (firstTel,1) );
sum2= sum2- (macroPeriod / repRate) * ( sortedArray (secondTel ,1) - sortedArray (firstTel,1) );
secondDifference = abs(sum1 - sum2);
if ( secondDifference < (firstDifference - 5) )
x = firstBP:repRate:macroPeriod;
basePeriod(x, 2) = basePeriod(x, 2) + sortedArray (secondTel ,1) - sortedArray (firstTel,1);
y = secondBP:repRate:macroPeriod;
basePeriod(y, 2) = basePeriod(y, 2) + sortedArray (firstTel,1) - sortedArray (secondTel ,1);
end
end
end
end
end
cglr on 4 Dec 2019
Sure.
I have one sorted array that keeps all messages in there.
Each messages have duration in microseconds and individual period in miliseconds. Messages are placed into each cycle looking at their individual period and duration. You can find one example below. My goal is to minimize duration of maximum cycle and to keep all of them in balanced.
In nested for loops I make comparison for all possibilities according to messages (1-2,1-3,...9-7,9-8), to find out is there any message that have bigger duration but placed in small duration cycle. Of course, there are any other constraints but this is the first step.
Is it more clear now ? J. Alex Lee on 3 Dec 2019
For nested loops you can keep as much outside of the inner loop as possible, in this case the search for placeOfFirst looks like it can be outside the inner loop?
At first glance it doesn't seem you can really get away from the nested structure, though maybe there is...
But it also looks like you may be spending a lot of time on redundant "find()" statements. It looks like you could pre-find the indices rather than find-ing each loop (for the inner find)
Not really an optimization, but to avoid nested if's this case, you can test for opposite of what you want and continue, since you don't have other bits of code happening after the if's
for i = size(telArray,1):-1:1
idx = find ( telArray(i,1) == sortedArray(:,3) ,1 );
placeof_a(i,1) = find(heuristic(:,idx)~=0,1);
end
for i = 1: totalCount
for j= 1: totalCount2
if telArray(i,1) == telArray(j,1)
continue
end
placeOfFirst = placeof_a(i);
placeOfSecond = placeof_a(j);
% ...
end
end
Does this work?