Summary The substitution method and iterative method are two distinct approaches used to solve recurrence relations in algorithm design. Understanding the difference between these methods is crucial for efficient problem-solving. The substitution method involves substituting the recurrence relation into itself until a pattern emerges, whereas the iterative method uses a loop to iteratively calculate the … Read more
Investigating iOS Firebase EXC_BAD_ACCESS KERN_INVALID_ADDRESS Crashes Summary This postmortem analyzes recurring EXC_BAD_ACCESS KERN_INVALID_ADDRESS interrupts impacting our iOS app. The crash manifests as invalid memory access attempts on freed objects during AppDelegate initialization, with incomplete/missing stack traces in Firebase Crashlytics reports and inconsistent breadcrumb data. Root Cause The primary failure occurs due to use-after-free memory violation. … Read more
Summary The Redisson RReadWriteLock is experiencing issues under high traffic, with errors indicating that none of the slaves were synced. Disabling the checkLockSyncedSlaves flag may improve lock acquisition latency, but it comes with trade-offs, including potential lock loss during failover. Root Cause The root cause of the issue is the asynchronous replication in Redis Cluster, … Read more
Summary When considering the use of pthread_mutex_t vs std::atomic_flag for achieving locks in a multi-threaded environment, especially in real-time systems, understanding the performance implications is crucial. The question revolves around the speed of acquiring a lock with pthread_mutex_t when the lock can be achieved immediately, and how it compares to using std::atomic_flag. Root Cause The … Read more
Summary Upgrading a C++17 codebase to C++20 using MSVC 2022 triggered a series of obscure compiler errors (C3878, C2760, C2065, C7510) in template-heavy code. The root cause was the two-phase name lookup changes introduced in C++20, specifically the requirement to use the typename keyword for dependent type names. The template code relied on pre-C++20 behaviors … Read more
Summary The question revolves around the optimization technique used in Excel’s Solver tool, specifically whether it’s more effective to double the max iterations or execute the Solver twice with a lower max iteration limit, starting from the result of the previous calculation. The author observed that executing Solver twice with reduced iterations led to consistent … Read more
Streamlit Service Interruption Postmortem: Persistent Execution Failure on Windows Terminals Summary A Streamlit application deployed on a Windows Server was designed for 24/7 availability but terminated unexpectedly upon terminal closure. The failure stemmed from misapplied daemonization approaches. Resolution involved implementing native Windows service management through NSSM to decouple app execution from terminal sessions. Root Cause … Read more
Summary When working with WiFi connections on devices like the ESP32, using the Arduino-IDE, a common question arises regarding the most efficient way to print data to the client. The options in question are: using multiple client.print() statements with a mix of strings and floats, or concatenating all the data into a single string before … Read more
Why two modes for tininess in IEEE754 Floating-point standard? Summary IEEE 754 defines two tininess detection modes (before rounding and after rounding) for determining underflow during floating-point operations. While the functional difference occurs in an extremely narrow numerical range (~2⁻¹⁵⁰ for single-precision), these modes offer flexibility to hardware designers in balancing precision requirements against implementation … Read more
Summary This article addresses a common issue in Power Automate where users need to group an array by one column and concatenate text in another column. The problem arises when working with arrays of objects and the requirement is to aggregate data based on a specific key. Root Cause The root cause of this issue … Read more