Ichthyostega
bdc1b089d7
- Result found in typically 6-7 steps; - running 20 instead of 30 samples seems sufficient Breaking point in this example at stress-Factor 0.47 with run-time 39ms
441 lines
16 KiB
C++
441 lines
16 KiB
C++
/*
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STRESS-TEST-RIG.hpp - setup for stress and performance investigation
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Copyright (C) Lumiera.org
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2024, Hermann Vosseler <Ichthyostega@web.de>
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This program is free software; you can redistribute it and/or
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modify it under the terms of the GNU General Public License as
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published by the Free Software Foundation; either version 2 of
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the License, or (at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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*/
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/** @file stress-test-rig.hpp
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** A test bench to conduct performance measurement series. Outfitted especially
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** to determine runtime behaviour of the Scheduler and associated parts of the
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** Lumiera Engine through systematic execution of load scenarios.
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**
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** # Scheduler Stress Testing
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**
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** The point of departure for any stress testing is to show that the subject will
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** break in controlled ways only. For the Scheduler this can easily be achieved by
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** overloading until job deadlines are broken. Much more challenging however is the
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** task to find out about the boundary of regular scheduler operation. This realm
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** can be defined by the ability of the scheduler to follow and conform to the
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** timings set out explicitly in the schedule. Obviously, short and localised
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** load peaks can be accommodated, yet once a persistent backlog builds up,
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** the schedule starts to slip and the calculation process will flounder.
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**
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** A method to determine such a _»breaking point«_ in a systematic way is based on
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** building a [synthetic calculation load](\ref test-chain-load.hpp) and establish
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** the timings of a test schedule based on a simplified model of expected computation
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** expense. By scaling and condensing these schedule timings, a loss of control can
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** be provoked, and determined by statistical observation: since the process of
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** scheduling contains an essentially random component, persistent overload will be
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** indicated by an increasing variance of the overall runtime, and a departure from
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** the nominal runtime of the executed schedule.
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**
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** ## Setup
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** To perform this test scheme, an operational Scheduler is required, and an instance
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** of the TestChainLoad must be provided, configured with desired load properties.
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** The _stressFactor_ of the corresponding generated schedule will be the active parameter
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** of this test, performing a binary search for the _breaking point._ The Measurement
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** attempts to narrow down to the point of massive failure, when the ability to somehow
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** cope with the schedule completely break down. Based on watching the Scheduler in
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** operation, the detection was linked to three conditions, which typically will
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** be triggered together, and within a narrow and reproducible parameter range:
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** - an individual run counts as _accidentally failed_ when the execution slips
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** away by more than 2ms with respect to the defined overall schedule. When more
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** than 55% of all observed runs are considered as failed, the first condition is met
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** - moreover, the observed ''standard derivation'' must also surpass the same limit
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** of > 2ms, which indicates that the Scheduling mechanism is under substantial
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** strain; in regular operation, the slip is rather ~ 200µs.
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** - the third condition is that the ''averaged delta'' has surpassed 4ms,
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** which is 2 times the basic failure indicator.
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**
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** ## Observation tools
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**
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** @see TestChainLoad_test
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** @see SchedulerStress_test
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*/
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#ifndef VAULT_GEAR_TEST_STRESS_TEST_RIG_H
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#define VAULT_GEAR_TEST_STRESS_TEST_RIG_H
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#include "vault/common.hpp"
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//#include "test-chain-load.hpp"
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//#include "lib/test/transiently.hpp"
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#include "vault/gear/scheduler.hpp"
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#include "lib/time/timevalue.hpp"
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//#include "lib/iter-explorer.hpp"
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#include "lib/meta/function.hpp"
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#include "lib/format-string.hpp"
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#include "lib/format-cout.hpp"//////////////////////////TODO RLY?
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//#include "lib/util.hpp"
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//#include <functional>
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#include <utility>
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//#include <memory>
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//#include <string>
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//#include <vector>
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#include <tuple>
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#include <array>
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namespace vault{
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namespace gear {
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namespace test {
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using util::_Fmt;
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using util::min;
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using util::max;
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// using util::isnil;
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// using util::limited;
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// using util::unConst;
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// using util::toString;
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// using util::isLimited;
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// using lib::time::Time;
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// using lib::time::TimeValue;
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// using lib::time::FrameRate;
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// using lib::time::Duration;
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// using lib::test::Transiently;
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// using lib::meta::_FunRet;
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// using std::string;
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// using std::function;
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using std::make_pair;
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using std::make_tuple;
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// using std::forward;
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// using std::string;
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// using std::swap;
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using std::move;
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namespace err = lumiera::error; //////////////////////////TODO RLY?
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namespace { // Default definitions ....
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}
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namespace stress_test_rig {
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template<class X, class P>
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struct _ValidateBinarySearchFun
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{
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static_assert (not sizeof(P), "Functor unsuitable for binary search. "
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"Expected signature pair<bool,X>(PAR)" );
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};
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template<class RES, class PAR>
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struct _ValidateBinarySearchFun<std::pair<bool,RES>(PAR), PAR>
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{
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using Result = RES;
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};
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template<class FUN, typename PAR>
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inline auto
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make_binarySearchResults()
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{
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using Sig = typename lib::meta::_Fun<FUN>::Sig;
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using Res = typename _ValidateBinarySearchFun<Sig,PAR>::Result;
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using Data = std::vector<std::pair<bool, Res>>;
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return Data{};
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}
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template<class FUN, class CON, typename PAR>
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inline auto
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binarySearch_impl (FUN&& fun, CON results, PAR lower, PAR upper, PAR epsilon)
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{
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REQUIRE (lower <= upper);
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while ((upper-lower) >= epsilon)
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{
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PAR div = lower + (upper-lower) / 2;
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results.emplace_back (fun(div));
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bool hit = results.back().first;
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if (hit)
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upper = div;
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else
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lower = div;
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cout<<"##################LOOP lower="<<lower<<" div="<<div<<" upper="<<upper<<" hit="<<hit<<endl;
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}
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return results;
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}
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template<class FUN, typename PAR>
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inline auto
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binarySearch_inner (FUN&& fun, PAR lower, PAR upper, PAR epsilon)
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{
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auto results = make_binarySearchResults<FUN,PAR>();
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return binarySearch_impl(forward<FUN> (fun), results, lower,upper,epsilon);
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}
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template<class FUN, typename PAR>
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inline auto
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binarySearch_upper (FUN&& fun, PAR lower, PAR upper, PAR epsilon)
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{
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REQUIRE (lower <= upper);
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auto results = make_binarySearchResults<FUN,PAR>();
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results.emplace_back (fun(upper));
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bool hit = results.back().first;
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if (not hit)
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{// the upper end breaks contract => search above
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PAR len = (upper-lower);
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lower = upper - len/10;
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upper = lower + 14*len/10;
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}
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return binarySearch_impl(forward<FUN> (fun), results, lower,upper,epsilon);
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}
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/**
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* Specific stress test scheme to determine the
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* »breaking point« where the Scheduler starts to slip
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*/
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template<class CONF>
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class BreakingPointBench
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: CONF
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{
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using TestLoad = decltype(std::declval<CONF>().testLoad());
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using TestSetup = decltype(std::declval<CONF>().testSetup (std::declval<TestLoad&>()));
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struct Res
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{
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double stressFac{0};
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double percentOff{0};
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double stdDev{0};
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double avgDelta{0};
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double avgTime{0};
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double expTime{0};
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};
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/** prepare the ScheduleCtx for a specifically parametrised test series */
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void
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configureTest (TestSetup& testSetup, double stressFac)
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{
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testSetup.withLoadTimeBase (CONF::LOAD_BASE)
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.withAdaptedSchedule(stressFac, CONF::CONCURRENCY);
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}
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/** perform a repetition of test runs and compute statistics */
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Res
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runProbes (TestSetup& testSetup, double stressFac)
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{
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auto sqr = [](auto n){ return n*n; };
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Res res;
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auto& [sf,pf,sdev,avgD,avgT,expT] = res;
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sf = stressFac;
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expT = testSetup.getExpectedEndTime() / 1000;
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std::array<double, CONF::REPETITIONS> runTime;
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for (uint i=0; i<CONF::REPETITIONS; ++i)
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{
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runTime[i] = testSetup.launch_and_wait() / 1000;
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avgT += runTime[i];
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}
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avgT /= CONF::REPETITIONS;
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avgD = fabs (avgT-expT);
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for (uint i=0; i<CONF::REPETITIONS; ++i)
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{
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sdev += sqr (runTime[i] - avgT);
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double delta = fabs (runTime[i] - expT);
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bool fail = (delta > CONF::FAIL_LIMIT);
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if (fail)
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++ pf;
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showRun(i, delta, runTime[i], runTime[i] > avgT, fail);
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}
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pf /= CONF::REPETITIONS;
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sdev = sqrt (sdev/CONF::REPETITIONS);
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showStep(res);
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return res;
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}
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/** criterion to decide if this test series constitutes a slipped schedule */
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bool
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decideBreakPoint (Res& res)
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{
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return res.percentOff > CONF::TRIGGER_FAIL
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and res.stdDev > CONF::TRIGGER_SDEV
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and res.avgDelta > CONF::TRIGGER_DELTA;
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}
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/**
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* invoke a binary search to produce a sequence of test series
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* with the goal to narrow down the stressFact where the Schedule slips away.
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*/
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template<class FUN>
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Res
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conductBinarySearch (FUN&& runTestCase)
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{
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auto results = binarySearch_upper (forward<FUN> (runTestCase), 0.0, CONF::UPPER_STRESS, CONF::EPSILON);
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uint s = results.size();
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ENSURE (s >= 2);
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Res res;
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auto& [sf,pf,sdev,avgD,avgT,expT] = res;
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// average data over the last three steps investigated for smoothing
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uint points = min (results.size(), 3u);
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for (uint i=results.size()-points; i<results.size(); ++i)
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{
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Res resx = results[i].second;
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pf += resx.percentOff;
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sdev += resx.stdDev;
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avgD += resx.avgDelta;
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avgT += resx.avgTime;
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expT += resx.expTime;
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}
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pf /= points;
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sdev /= points;
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avgD /= points;
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avgT /= points;
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expT /= points;
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// »breaking point« stress in the middle of the last interval
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sf = (results[s-1].second.stressFac + results[s-2].second.stressFac) / 2;
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return res;
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}
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_Fmt fmtRun_ {"....·%-2d: Δ=%4.1f t=%4.1f %s %s"}; // i % Δ % t % t>avg? % fail?
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_Fmt fmtStep_{ "%4.2f| : ∅Δ=%4.1f±%-4.2f ∅t=%4.1f %%%3.1f -- expect:%4.1fms"}; // stress % ∅Δ % σ % ∅t % fail % t-expect
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_Fmt fmtResSDv_{"%9s= %5.2f ±%4.2f%s"};
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_Fmt fmtResVal_{"%9s: %5.2f%s"};
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void
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showRun(uint i, double delta, double t, bool over, bool fail)
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{
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if (CONF::showRuns)
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cout << fmtRun_ % i % delta % t % (over? "+":"-") % (fail? "●":"○")
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<< endl;
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}
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void
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showStep(Res& res)
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{
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if (CONF::showStep)
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cout << fmtStep_ % res.stressFac % res.avgDelta % res.stdDev % res.avgTime % res.percentOff % res.expTime
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<< endl;
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}
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void
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showRes(Res& res)
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{
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if (CONF::showRes)
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{
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cout << fmtResVal_ % "stresFac" % res.stressFac % "" <<endl;
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cout << fmtResVal_ % "fail" %(res.percentOff * 100) % '%' <<endl;
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cout << fmtResSDv_ % "delta" % res.avgDelta % res.stdDev % "ms"<<endl;
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cout << fmtResVal_ % "runTime" % res.avgTime % "ms"<<endl;
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cout << fmtResVal_ % "expected" % res.expTime % "ms"<<endl;
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}
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}
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void
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showRef(TestLoad& testLoad)
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{
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if (CONF::showRef)
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cout << fmtResVal_ % "refTime"
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% (testLoad.calcRuntimeReference(CONF::LOAD_BASE) /1000)
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% "ms" << endl;
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}
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public:
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/**
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* Launch a measurement sequence to determine the »breaking point«
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* for the configured test load and parametrisation of the Scheduler.
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* @return a tuple `[stress-factor, ∅delta, ∅run-time]`
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*/
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auto
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searchBreakingPoint()
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{
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TRANSIENTLY(work::Config::COMPUTATION_CAPACITY) = CONF::CONCURRENCY;
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TestLoad testLoad = CONF::testLoad().buildTopology();
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TestSetup testSetup = CONF::testSetup (testLoad);
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auto performEvaluation = [&](double stressFac)
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{
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configureTest (testSetup, stressFac);
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auto res = runProbes (testSetup, stressFac);
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return make_pair (decideBreakPoint(res), res);
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};
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Res res = conductBinarySearch (move (performEvaluation));
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showRes (res);
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showRef (testLoad);
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return make_tuple (res.stressFac, res.avgDelta, res.avgTime);
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}
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};
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}//namespace stress_test_rig
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/** configurable template for running Scheduler Stress tests */
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class StressRig
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: util::NonCopyable
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{
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public:
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using usec = std::chrono::microseconds;
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usec LOAD_BASE = 500us;
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uint CONCURRENCY = work::Config::getDefaultComputationCapacity();
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double EPSILON = 0.01; ///< error bound to abort binary search
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double UPPER_STRESS = 0.6; ///< starting point for the upper limit, likely to fail
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double FAIL_LIMIT = 2.0; ///< delta-limit when to count a run as failure
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double TRIGGER_FAIL = 0.55; ///< %-fact: criterion-1 failures above this rate
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double TRIGGER_SDEV = FAIL_LIMIT; ///< in ms : criterion-2 standard derivation
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double TRIGGER_DELTA = 2*FAIL_LIMIT; ///< in ms : criterion-3 delta above this limit
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bool showRuns = false; ///< print a line for each individual run
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bool showStep = true; ///< print a line for each binary search step
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bool showRes = true; ///< print result data
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bool showRef = true; ///< calculate single threaded reference time
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static uint constexpr REPETITIONS{20};
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BlockFlowAlloc bFlow{};
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EngineObserver watch{};
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Scheduler scheduler{bFlow, watch};
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/** Extension point: build the computation topology for this test */
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auto
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testLoad()
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{
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return TestChainLoad<>{64};
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}
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/** (optional) extension point: base configuration of the test ScheduleCtx */
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template<class TL>
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auto
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testSetup (TL& testLoad)
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{
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return testLoad.setupSchedule(scheduler)
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.withJobDeadline(100ms)
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.withUpfrontPlanning();
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}
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/**
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* Entrance Point: build a stress test measurement setup
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* to determine the »breaking point« where the Scheduler is unable
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* to keep up with the defined schedule.
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* @tparam CONF specialised subclass of StressRig with customisation
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* @return a builder to configure and then launch the actual test
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*/
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template<class CONF>
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static auto
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with()
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{
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return stress_test_rig::BreakingPointBench<CONF>{};
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}
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};
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}}} // namespace vault::gear::test
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#endif /*VAULT_GEAR_TEST_STRESS_TEST_RIG_H*/
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