myArray count isn't functioning as expected - objective-c

Question

The arrayTwelveLEngth variable isn't working as expected. When I placed a breakpoint on the amount = 1; line above, I hovered over arrayTwelve, and found that it was empty with 0 elements. Immediately after, I then hovered about arrayTwelveLength, expecting to see 0, but instead it seems that the arrayTwelveLength had a value of 1876662112. I don't know how it got that value, and I need to solve that problem. What am I doing wrong?
NSMutableArray *redValues = [NSMutableArray array];
NSMutableArray *arrayTwelve = [NSMutableArray array];
__block int counter = 0;
__block NSInteger u;
NSUInteger redValuesLength = [redValues count];
__block int arrayTwelveLength = 0;
__block float diffForAverage, fps, averageTime, bloodSpeed;
float average;
__block int amount = 1;
__block float totalTwelve, totalThirteen;
__block NSUInteger totalNumberOfFramesInSmallArrays = 0;
__block NSUInteger totalNumberOfFramesNotInSmallArrays;
for (u = (counter + 24); u < (redValuesLength - 24); u++)
{
diffForAverage = average - [redValues[u + 1] floatValue];
float test = [redValues[u] floatValue];
arrayTwelveLength = [arrayTwelve count];
if (diffForAverage > -1 && diffForAverage < 1)
{
totalTwelve += [redValues[u + 1] floatValue];
amount++;
[arrayTwelve addObject:#(test)];
counter++;
}
else
{
if (arrayTwelveLength >= 8)
{
counter++;
break;
}
else
{
[arrayTwelve removeAllObjects];
totalTwelve = [redValues[u + 1] floatValue];
counter++;
amount = 1;
}
}
}
amount = 1; // I added a breakpoint here
totalThirteen = [redValues[u + 1] floatValue];
average = totalThirteen / amount;
if (counter == redValuesLength)
{
totalNumberOfFramesNotInSmallArrays = redValuesLength - totalNumberOfFramesInSmallArrays - 25 - (redValuesLength - counter);
fps = redValuesLength / 30;
averageTime = totalNumberOfFramesNotInSmallArrays / fps;
bloodSpeed = 3 / averageTime;
[_BloodSpeedValue setText:[NSString stringWithFormat:#"%f", bloodSpeed]];
}
if (arrayTwelveLength == NULL)
{
arrayTwelveLength = 0;
}
totalNumberOfFramesInSmallArrays += arrayTwelveLength;

Answer 1

You have problems with unsigned/signed types and with your data set the first for loop should not even enter, because your for loop index variable u (== 24) < (redValuesLength (== 0) - 24) but, because redValuesLength being Unsigned type it wraps around and you get:
(unsigned long)0 - (unsigned long)24 = -24 modulo ULONG_MAX + 1= 18446744073709551592
Also, you are not initialising average before usage.