Big Data - Exercises 2

map(key,value):
// key: file_id; value: list of integers
maxVal =0
for i in values:
    if(i > maxVal):
        maxVal = i
emit(key, maxVal)

reduce(key, values):
// key: file_id; values: list of maxVal
finalMaxVal = 0
for i in values:
    if(i > finalMaxVal):
        finalMaxVal = i
emit(‘MaxVal’, finalMaxVal)

map(key, value):
// key: file _id: values: list of integers
sum = 0;
count = 0;

for i in value:
    sum = sum + i
    count = count + 1

emit(key, (sum,count)])

reduce(key, (sum,count)):
// key: file_id ; (sum,count): contains a list of sum & count pairs produced by each
// mapper task

sumTotal = 0
countTotal = 0

for (sumVal, countVal) in sum_count_list:
    sumTotal = sumTotal + sumVal
    counTotal = countTotal + countVal
average = sumTotal / countTotal
emit(‘AverageVal’, average)

map(key, value):
# key: file_id: values: list of integers

    for i in value:
        emit(i,1)

reduce(key, ):
# key: file_id ; : contains a list of integers & 1 (denoting its occurrence)

    #maps integers to their counts
    int2count = {}

    for ((i,1) in ):
        int2count[i] = int2count.get(i,0) + 1

emit(int2count)