microbenchmark

The Problem Lets say I have this function: function hog($i = 1) // uses $i * 0.5 MiB, returns $i * 0.25 MiB { $s = str_repeat('a', $i * 1024 * 512); return substr($s, $i * 1024 * 256); } I would like to call it and be able to inspect the maximum amount of memory it uses. In other words: memory_get_function_peak_usage($callback); . Is this possible? What I Have Tried I'm using the following values as my non-monotonically increasing $i argument for hog() : $iterations = array_merge(range(0, 50, 10), range(50, 0, 5)); $iterations = array_fill_keys($iterations, 0); Which is essentially: ( [0] => 0

I'm on an IvyBridge. I found the performance behavior of jnz inconsistent in inner loop and outer loop. The following simple program has an inner loop with fixed size 16: global _start _start: mov rcx, 100000000 .loop_outer: mov rax, 16 .loop_inner: dec rax jnz .loop_inner dec rcx jnz .loop_outer xor edi, edi mov eax, 60 syscall perf tool shows the outer loop runs 32c/iter. It suggests the jnz requires 2 cycles to complete. I then search in Agner's instruction table, conditional jump has 1-2 "reciprocal throughput", with a comment "fast if no jump". At this point I start to believe the above

In benchmarking some Java code on a Solaris SPARC box, I noticed that the first time I call the benchmarked function it runs EXTREMELY slowly (10x difference): First | 1 | 25295.979 ms Second | 1 | 2256.990 ms Third | 1 | 2250.575 ms Why is this? I suspect the JIT compiler, is there any way to verify this? Edit: In light of some answers I wanted to clarify that this code is the simplest possible test-case I could find exhibiting this behavior. So my goal isn't to get it to run fast, but to understand what's going on so I can avoid it in my real benchmarks. Solved: Tom Hawtin correctly pointed

I was recently profiling my code and found one interesting bottleneck in it. Here is benchmark : @BenchmarkMode(Mode.Throughput) @Fork(1) @State(Scope.Thread) @Warmup(iterations = 10, time = 1, timeUnit = TimeUnit.SECONDS) @Measurement(iterations = 10, time = 1, timeUnit = TimeUnit.SECONDS) public class Contains { private int[] ar = new int[] {1,2,3,4,5,6,7}; private int val = 5; @Benchmark public boolean naive() { return contains(ar, val); } @Benchmark public boolean lambdaArrayStreamContains() { return Arrays.stream(ar).anyMatch(i -> i == val); } @Benchmark public boolean

considering this example: public static void main(final String[] args) { final List<String> myList = Arrays.asList("A", "B", "C", "D"); final long start = System.currentTimeMillis(); for (int i = 1000000; i > myList.size(); i--) { System.out.println("Hello"); } final long stop = System.currentTimeMillis(); System.out.println("Finish: " + (stop - start)); } vs public static void main(final String[] args) { final List<String> myList = Arrays.asList("A", "B", "C", "D"); final long start = System.currentTimeMillis(); final int size = myList.size(); for (int i = 1000000; i > size; i--) { System.out

I have a microbenchmark that shows very strange results: @BenchmarkMode(Mode.Throughput) @Fork(1) @State(Scope.Thread) @Warmup(iterations = 10, time = 1, timeUnit = TimeUnit.SECONDS, batchSize = 1000) @Measurement(iterations = 40, time = 1, timeUnit = TimeUnit.SECONDS, batchSize = 1000) public class Chaining { private String a1 = "111111111111111111111111"; private String a2 = "222222222222222222222222"; private String a3 = "333333333333333333333333"; @Benchmark public String typicalChaining() { return new StringBuilder().append(a1).append(a2).append(a3).toString(); } @Benchmark public String

I am using the library Crypto++ 5.6.5 and Visual Studio 2017. How can I calculate the encryption time for AES-CCM? I would like to know how to calculate the encryption time for AES-CCM. The Crypto++ wiki provides an article Benchmarks . It provides a lot of details regarding library performance, how throughput is calculated, and it even references the source code where the actual throughput is measured. Believe it or not, a simple call to clock works just fine to measure bulk encryption. Also see Benchmarks | Timing Loop in the same wiki article. To benchmark AES/CCM, do something like the

While analyzing the results of a recent question here , I encountered a quite peculiar phenomenon: apparently an extra layer of HotSpot's JIT-optimization actually slows down execution on my machine. Here is the code I have used for the measurement: @OutputTimeUnit(TimeUnit.NANOSECONDS) @BenchmarkMode(Mode.AverageTime) @OperationsPerInvocation(Measure.ARRAY_SIZE) @Warmup(iterations = 2, time = 1) @Measurement(iterations = 5, time = 1) @State(Scope.Thread) @Threads(1) @Fork(2) public class Measure { public static final int ARRAY_SIZE = 1024; private final int[] array = new int[ARRAY_SIZE];