The whole point of a websocket connection is that you don’t ever have to ping the app for changes. Instead, the client just connects once and then the server can just directly send the client changes whenever they are available. The client never has to ask. The server just sends data when it’s available. For … Read more
Google Tag Manager is by definition a performance impediment. Its only purpose is to allow non-technical people to dump random garbage very important third-party scripts on a site. If you bypass GTM by inserting the external tags/scripts that you want on your site directly, it will improve performance immediately. If you can’t do that, you … Read more
I have looked for actual data for the past days, and found nothing. However, I did some research, which compares the cost of atomic ops with the costs of cache misses. The cost of the x86 LOCK prefix, (including lock cmpxchg for atomic CAS), before PentiumPro (as described in the doc), is a memory access … Read more
CPU register is always faster than the L1 cache. It is the closest. The difference is roughly a factor of 3. Trying to make this as intuitive as possible without getting lost in the physics underlying the question: there is a simple correlation between speed and distance in electronics. The further you make a signal … Read more
You ask two different questions: learning and performance. It took me about a month to become comfortable with functional programming using recursion, pattern matching, map, filter, and fold. I did all that with ML but it translated to Haskell very easily. It took me two or three years to wrap my head around monads, but … Read more
One way of looking at this is to say that transport latency + processing time = response time. Transport latency is the time it takes for a request/response to be transmitted to/from the processing component. Then you need to add the time it takes to process the request. As an example, say that 5 people … Read more
Here are optimization levels for the Swift compiler’s code generation (you can find them in Build Settings): [-Onone] no optimizations, the default for debug. [-O] perform optimizations, the default for release. [-Ofast] perform optimizations and disable runtime overflow checks and runtime type checks. Using your code I got these times at different levels of optimization: … Read more
TL;DR The discrepancy you are observing between RDTSC and REFTSC and is due to TurboBoost P-state transitions. During these transitions, most of the core, including the fixed-function performance counter REF_TSC, is halted for approximately 20000-21000 cycles (8.5us), but rdtsc continues at its invariant frequency. rdtsc is probably in an isolated power and clock domain because … Read more
Introduction The debate on whether bsxfun is better than repmat or vice versa has been going on like forever. In this post, we would try to compare how the different built-ins that ship with MATLAB fight it out against repmat equivalents in terms of their runtime performances and hopefully draw some meaningful conclusions out of … Read more
a[i] = i simply assigns the value i to a[i]. This is not appending, it’s just a simple assignment. Now the append: a = append(a, i) In theory the following happens: This calls the builtin append() function. For that, it first has to copy the a slice (slice header, backing array is not part of … Read more