Add more options to measure_cost_variation

soroban-env-host/benches/common/measure.rs

@@ -451,10 +451,21 @@ pub fn measure_worst_case_costs<HCM: HostCostMeasurement>(
     })
 }
 
+/// Measure the cost variation of a HCM. `sweep_input` specifies whether the input
+/// is fixed or randomized. 
+///     if true - input is randomized, with `large_input` specifying the upperbound
+///               of the input size
+///     if false - input size is fixed at `large_input`
+/// `iteration` specifies number of iterations to run the measurement
+/// `include_best_case` specifies whether best case is included. Often the best case
+/// is a trivial case that isn't too relevant (and never hit). So if one is more 
+/// interested in the worst/average analysis, it might be useful to throw it away.
 pub fn measure_cost_variation<HCM: HostCostMeasurement>(
     large_input: u64,
+    iterations: u64,
+    sweep_input: bool,
+    include_best_case: bool,    
 ) -> Result<Measurements, std::io::Error> {
-    let count = 100;
     let mut i = 0;
     let mut rng = StdRng::from_seed([0xff; 32]);
 
@@ -476,11 +487,19 @@ pub fn measure_cost_variation<HCM: HostCostMeasurement>(
     let measurements = measure_costs_inner::<HCM, _, _>(
         |host| {
             i += 1;
+            let input = if sweep_input {
+                rng.gen_range(1..=2 + large_input)
+            } else {
+                large_input
+            };
             match i {
-                1 => Some(HCM::new_best_case(host, &mut rng)),
+                1 => if include_best_case {
+                    Some(HCM::new_best_case(host, &mut rng))
+                } else {
+                    Some(HCM::new_random_case(host, &mut rng, input))
+                }                
                 2 => Some(HCM::new_worst_case(host, &mut rng, large_input)),
-                n if n < count => {
-                    let input = rng.gen_range(1..=2 + large_input);
+                n if n < iterations => {
                     Some(HCM::new_random_case(host, &mut rng, input))
                 }
                 _ => None,

soroban-env-host/benches/variation_histograms.rs

@@ -7,7 +7,7 @@ use soroban_env_host::cost_runner::CostRunner;
 struct LinearModelTables;
 impl Benchmark for LinearModelTables {
     fn bench<HCM: HostCostMeasurement>() -> std::io::Result<(FPCostModel, FPCostModel)> {
-        let mut measurements = measure_cost_variation::<HCM>(100)?;
+        let mut measurements = measure_cost_variation::<HCM>(100, 1000, false, false)?;
         measurements.check_range_against_baseline(&HCM::Runner::COST_TYPE)?;
         measurements.preprocess();
         measurements.report_histogram("cpu", |m| m.cpu_insns);