Avoid array overrwriting

Question

I have this piece of code, within my Main method:

for(int i = 0; i < 2; i++){
            double psd = JMath.sqrt((((4*cc)/(JMath.pow((1 + 6*frequency[i]*cc), (double) 5/3)))*df));              
            double cohC = H*JMath.sqrt((frequency[i]/A.averageHubWindSpeed)*(frequency[i]/A.averageHubWindSpeed) + (.12/Lc)*(.12/Lc));          
            BLAS.getInstance().sscal(packDistance.length, (float) cohC,packDistance, 1);    
}

This way packDistance is overwritten, so for i == 1, sscal will multiply cohC with the packDistance stemming from the sscal at i == 0. Instead, I want packDistance to hold the same original values, which are assigned outside the loop.

How could I overtake this issue?

Well, copy the array to another before entering the for loop and use that copy. Look at Arrays.copyOf(). — fge
– fge, Commented Jun 28, 2013 at 10:06
Maybe it's just me, but I am unable to understand what you're trying to do. A more complete (self-contained) code sample and explanation with examples of desired value and actual value always helps. And your code seems unnecessarily complicated to reproduce the problem - you surely could've replaced the two equations with something a lot simpler. — Bernhard Barker
– Bernhard Barker, Commented Jun 28, 2013 at 10:12

voidMainReturn · Accepted Answer · 2013-06-28 10:24:33Z

2

You can use java's Arrays.copyOf() method as follows :

T[] arr2 = Arrays.copyOf(packDistance,packDistance.length);
for(int i = 0; i < 2; i++){
            double psd = JMath.sqrt((((4*cc)/(JMath.pow((1 + 6*frequency[i]*cc), (double) 5/3)))*df));              
            double cohC = H*JMath.sqrt((frequency[i]/A.averageHubWindSpeed)*(frequency[i]/A.averageHubWindSpeed) + (.12/Lc)*(.12/Lc));          
            BLAS.getInstance().sscal(packDistance.length, (float) cohC,packDistance, 1);    
}

where T is the data type of the array you are trying to copy. Here is an example of usage of Arrays.copyOf().

answered Jun 28, 2013 at 10:24

voidMainReturn

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