Introduce Warm-up Phase for Dudect Measurement

A warm-up step was added to the measurement function to discard the
first batch of data, inspired by a privately implemented earlier
version that passed tests for queue-related functions. This follows the
approach described in the Dudect paper, which skips initial measurements
to improve timing stability., potentially mitigating factors like cache
misses or allocation delays. Unlike the author's GitHub implementation,
which dynamically checks the percentiles array state for each call, a
static boolean is used here to mark the first execution within a single
test run, as this suits the fixed iteration structure of the testing
loop. Tests using queue insertion and removal functions showed no
notable difference in constant-time behavior with or without this step
after memory leaks were fixed, but it is retained for potential
improvements in t-test precision under different test conditions.

Change-Id: Ieec138264fdd8d087142cdf3c3e9f961f521e80b

Author: HeatCrab

dudect/fixture.c

@@ -196,8 +196,20 @@ static bool doit(int mode)
     bool ret = measure(before_ticks, after_ticks, input_data, mode);
     differentiate(exec_times, before_ticks, after_ticks);
     prepare_percentiles(exec_times, percentiles);
-    update_statistics(exec_times, classes, percentiles);
-    ret &= report();
+
+    /* This warm-up step discards the first measurement batch by skipping
+     * its statistical analysis. A static boolean flag controls this by
+     * marking the initial execution, ensuring only the first call within
+     * a test run is excluded from the t-test computation.
+     */
+    static bool first_time = true;
+    if (first_time) {
+        first_time = false;
+        ret = true;
+    } else {
+        update_statistics(exec_times, classes, percentiles);
+        ret &= report();
+    }
 
     free(before_ticks);
     free(after_ticks);