CODEWITHSUNDEEP
pythonalgorithmperformancenetwork-programmingoperating-system
Mr.Selva Kumar
Mr.Selva Kumar

Reputation: 11

how to reduce running time in python?

I have the following program which generates 100 million mac's and append it into the list.

But the 100 million mac's generation and insertion itself takes ~7 Minutes in python???

    import datetime
    def mac_gen():
    hex_byte1=0
    hex_byte2=0
    hex_byte3=0
    hex_byte4=0
    hex_byte5=0
    hex_byte6=0
    hex_byte7=0
    hex_byte8=0
    hex_byte9=0
    hex_byte10=0
    hex_byte11=0
    hex_byte12=0
    total_mac = 0
    for hex_byte_12 in range(0,16):
        for hex_byte11 in range(0,16):
            for hex_byte10 in range(0,16):
                for hex_byte9 in range(0,16):
                    for hex_byte8 in range(0,16):
                        for hex_byte7 in range(0,16):
                            for hex_byte6 in range(0,16):
                                for hex_byte5 in range(0,16):
                                    for hex_byte4 in range(0,16):
                                        for hex_byte3 in range(0,16):
                                            for hex_byte2 in range(0,16):
                                                for hex_byte1 in range(0,16):
                                                    total_mac +=1;
                                                    if total_mac > number_of_mac_to_print:
                                                       return
                                                    mac_list.append("%X%X:%X%X:%X%X:%X%X:%X%X:%X%X" %(hex_byte_12,hex_byte11,hex_byte10,hex_byte9,hex_byte8,hex_byte7,hex_byte6,hex_byte5,hex_byte4,hex_byte3,hex_byte2,hex_byte1))

mac_list=list()
number_of_mac_to_print = 100000000
print(datetime.datetime.utcnow())
mac_gen()
print(datetime.datetime.utcnow())
print(len(mac_list))

Output:

2018-03-09 07:15:41.650460 <--- time stamp before calling mac_gen method

2018-03-09 07:22:33.902744 <--- time stamp after calling mac_gen method

100000000 . <---- total entries. 100 million

so question is:

  1. how to reduce the running time from 7 minutes to lowest as possible in python?

  2. if the same problem i am solving in C or C plus plus give please give me generrfic solution for that as well?

  3. when running the same code for 1 Billion mac it is terminating automatically i belive. and taking much more time. how to achive for 1 Billion mac generation?

Thanks in advance

Upvotes: 1

Views: 637

Answers (3)

user1196549
user1196549

Reputation:

Are you sure you want to do that ? All 12 digit hex numbers would fill up the largest supercomputer (281474976710656 values). Actually, all first 100000000 addresses have a zero for the first five digits (as 16^7 = 268435456).

Do you really need to store all these addresses ? If yes, I would recommend to use a single range(100000000) and leave the values as integers, only convert to hex when needed. This will spare a lot of space.

If not possible, it is probably more efficient to work with a string of 12 hex characters that you increment yourself rather than using a costly formatting operation.

And please, don't store those 500000000 ':' useless separators.

Upvotes: 1

r3mainer
r3mainer

Reputation: 24547

The long running times you're experiencing are quite likely to result from memory being paged out to your hard drive in order to make room for the addition of new items to mac_list.

I can't think of any good reason why you would need to store all these MACs in memory. They're numbered consecutively, so you can easily generate them on the fly:

gen_mac = lambda n: ":".join([("%012X" % n)[i:i+2] for i in range(0,12,2)])

Then instead of fetching items from mac_list, just use this function instead. In other words, replace

m = mac_list[12345678]

with

m = gen_mac(12345678)

Upvotes: 5

SaiBot
SaiBot

Reputation: 3745

The following code takes 3:20 on my laptop

mac_list=list()
for i in range(0, 100000000):
    strHex = hex(i)[2:].rjust(12, '0')
    mac_list.append(strHex[0:2] + ":"+strHex[2:4] + ":"+strHex[4:6] + ":"+strHex[6:8] + ":"+strHex[8:10] + ":"+strHex[10:12])

Upvotes: 1

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