Add bench common file

benchmarks/bench_common.nim

@@ -0,0 +1,37 @@
+import random, times, stats, strformat, math
+
+proc warmup*() =
+  # Warmup - make sure cpu is on max perf
+  let start = cpuTime()
+  var foo = 123
+  for i in 0 ..< 300_000_000:
+    foo += i*i mod 456
+    foo = foo mod 789
+
+  # Compiler shouldn't optimize away the results as cpuTime rely on sideeffects
+  let stop = cpuTime()
+  echo &"Warmup: {stop - start:>4.4f} s, result {foo} (displayed to avoid compiler optimizing warmup away)"
+
+template printStats*(experiment_name: string, compute_result: typed) {.dirty.} =
+  echo "\n" & experiment_name
+  echo &"Collected {stats.n} samples in {global_stop - global_start:>4.3f} seconds"
+  echo &"Average time: {stats.mean * 1000 :>4.3f} ms"
+  echo &"Stddev  time: {stats.standardDeviationS * 1000 :>4.3f} ms"
+  echo &"Min     time: {stats.min * 1000 :>4.3f} ms"
+  echo &"Max     time: {stats.max * 1000 :>4.3f} ms"
+  echo &"Theoretical perf: {a.size.float / (float(10^6) * stats.mean):>4.3f} MFLOP/s"
+  echo "\nDisplay computation result to make sure it's not optimized away"
+  echo compute_result # Prevents compiler from optimizing stuff away
+
+template bench*(name: string, compute_result: typed, body: untyped) {.dirty.}=
+  block: # Actual bench
+    var stats: RunningStat
+    let global_start = cpuTime()
+    for _ in 0 ..< nb_samples:
+      let start = cpuTime()
+      block:
+        body
+      let stop = cpuTime()
+      stats.push stop - start
+    let global_stop = cpuTime()
+    printStats(name, compute_result)