Parse 10GB Log and Count PCIe Errors | Dataford Interview Questions

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Problem

An AMD EPYC system can produce log files too large to load into memory at once. Write a function that streams log lines and counts occurrences of selected PCIe error codes.

Each relevant log entry contains the exact pattern PCIe_ERROR code=CODE, where CODE consists only of uppercase letters, digits, underscores, and hyphens. Ignore lines without this pattern and ignore codes that are not in the requested set. A line contains at most one PCIe error entry.

Formal Specification

Implement count_pcie_errors(lines, error_codes).

lines is an iterable of strings, such as a file object. The function must process it incrementally and must not convert the complete input into a list.
error_codes is a list of distinct strings identifying codes to count.
Return a dictionary mapping every requested code to its frequency, including codes with frequency zero.

Constraints

1 <= len(error_codes) <= 10^4
The total log size can be approximately 10 GB
Each line contains at most 10^4 characters
Error codes are case-sensitive
Input lines may contain malformed or unrelated text
Each line contains at most one PCIe error entry

Function Signature

def count_pcie_errors(lines, error_codes):