Process hangs from big stdin

[MartinXPN]

https://profound.academy/armenian-spoj/kVlW3xG5g1Ix6diXJQJT
This problem has big inputs (>1MB) and that freezes the process when passing stdin.
We should debug and fix this issue.

[MartinXPN]

Tried to do cat input | program but cat is super slow and results in TLE even if the program was actually optimal.

Might need to try using fifo

Even this program results in TLE:

n, m = map(int, input().split())
for i in range(n):
    a = input().split()
    assert len(a) == m

k = int(input())
for i in range(k):
    a = input().split()
    assert len(a) == 2
    print('YES')

[MartinXPN]

Seems like the issue is with stdout rather than stdin as this program does not hang:

n, m = map(int, input().split())
print('n:', n)
print('m:', m)

for i in range(n):
    a = input().split()
    assert len(a) == m
print('getting queries...')

k = int(input())
for i in range(k):
    a = input().split()
    assert len(a) == 2
    if i == 0:
        print('i:', i, '=>', a)
    if i == k - 1:
        print('i:', i, '=>', a)

https://www.reddit.com/r/Python/comments/1vbie0/subprocesspipe_will_hang_indefinitely_if_stdout/

https://bugs.python.org/issue41586

[MartinXPN]

We probably need to upgrade the python version to 3.10 to be able to use the feature providing pipesize to subprocess.Popen.
https://docs.python.org/3/library/subprocess.html#popen-constructor

Reference: python/cpython@23c0fb8

When a pipe is full it blocks for writing.
When a pipe is empty it blocks for reading. On processes that are
very fast this can lead to a lot of wasted CPU cycles. On a typical
Linux system the max pipe size is 1024K which is much better.
For high performance-oriented libraries such as xopen it is nice to
be able to set the pipe size.

The workaround without this feature is to use my_popen_process.stdout.fileno() in
conjuction with fcntl and 1031 (value of F_SETPIPE_SZ) to acquire this behavior.

The problem is that AWS team seems to not care about python 3.10 support that much: aws/aws-lambda-base-images#31