Evening all,
Using Obj-C, I'm working out all the permutations of 0 and 1 for a given number of elements in an array. For example, if you had an array length of 4, the permutations would be:
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| Code: 2012-08-19 01:26:46.528 Permutation Creator[9822:303] 0000 2012-08-19 01:26:46.530 Permutation Creator[9822:303] 0001 2012-08-19 01:26:46.530 Permutation Creator[9822:303] 0010 2012-08-19 01:26:46.530 Permutation Creator[9822:303] 0011 2012-08-19 01:26:46.531 Permutation Creator[9822:303] 0100 2012-08-19 01:26:46.531 Permutation Creator[9822:303] 0101 2012-08-19 01:26:46.532 Permutation Creator[9822:303] 0110 2012-08-19 01:26:46.532 Permutation Creator[9822:303] 0111 2012-08-19 01:26:46.532 Permutation Creator[9822:303] 1000 2012-08-19 01:26:46.533 Permutation Creator[9822:303] 1001 2012-08-19 01:26:46.533 Permutation Creator[9822:303] 1010 2012-08-19 01:26:46.533 Permutation Creator[9822:303] 1011 2012-08-19 01:26:46.534 Permutation Creator[9822:303] 1100 2012-08-19 01:26:46.534 Permutation Creator[9822:303] 1101 2012-08-19 01:26:46.534 Permutation Creator[9822:303] 1110 2012-08-19 01:26:46.535 Permutation Creator[9822:303] 1111 | |
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Now, I'm trying to do the same with an array with the size 49152, and it's going to take a while...I've got four cores in this iMac, so why not use them?
It's been ages since I've done anything about concurrency, and it was only really touched on in Java with regards to GUI programming.
The methods I'm using looks something like this:
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| Code: #define FALSE 0 #define TRUE 1 #define ARRAY_SIZE 49152 #define LAST_ARRAY_ELEMENT ARRAY_SIZE - 1 @interface PermutationCreator : NSObject{ NSMutableArray *permutations; int position; //Hold position in array int holder; //Hold value to be changed int end_not_reached; } @end @implementation PermutationCreator -(void)calculate{ [self print]; position = LAST_ARRAY_ELEMENT; [self addOne]; if(end_not_reached){ [self calculate]; }else{ [self print]; } } -(void)addOne{ holder = [[permutations objectAtIndex:position] intValue]; //Test if the end has been reached if((position == 0) && (holder == 1)){ end_not_reached = FALSE; return; } //If holder == 0, change to 1 and leave the rest as is if(holder == 0){ holder = 1; [permutations replaceObjectAtIndex:position withObject:[NSNumber numberWithInt:holder]]; return; } //If holder == 1, change to 0 and rerun this method if(holder == 1){ holder = 0; [permutations replaceObjectAtIndex:position withObject:[NSNumber numberWithInt:holder]]; position--; [self addOne]; } } @end | |
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So, two questions:
1) Is this type of work possible to do concurrently?
2) How might a concurrent way look? I'm presumably going to be doing some blocks/GCD stuff...
Many thanks,
Ben
