nx_cost_oracle.nx source

1// nx_cost_oracle.nx -- bits-up DETERMINISTIC measurement for fair performance head-to-heads (operator: 2// "avoid the pitfalls of emulators and all the other stuff"). The emulator/timing pitfall: wall-clock 3// and emulated cycle counts are NON-deterministic (vary by machine, emulator, cache, frequency scaling), 4// so judging speed by time is BIASED -- the same two programs can flip winners across runs. The fix, 5// from the hardware up: judge by a COUNTED INVARIANT that is identical every run -- retired instruction 6// count, gate-toggle (switching) activity, or bytes moved. The cost oracle REFUSES to render a verdict 7// on a non-deterministic metric. This is the performance arm of the Referee's DETERMINISM gate. 8// license_tier: ORIGINAL Pairs with nx_referee (fair judging) + nx_gate_energy (toggles) + nx_uops_cost. 9 10import "nx_syscalls.nx" 11 12const CO_WALLCLOCK: i64 = 0 // wall-clock / emulated time -- NON-deterministic -> UNFAIR to judge on 13const CO_INSN: i64 = 1 // retired instruction count -- deterministic 14const CO_TOGGLES: i64 = 2 // gate switching activity -- deterministic, hardware-portable 15const CO_BYTES: i64 = 3 // memory bytes moved -- deterministic 16 17const CO_REJECT: i64 = 0 - 1 // refuse to judge (non-deterministic metric) 18const CO_TIE: i64 = 0 19const CO_A_FASTER: i64 = 1 20const CO_B_FASTER: i64 = 2 21 22// a metric is FAIR for head-to-head only if DETERMINISTIC (same input -> same value every run). 23func co_metric_deterministic(kind: i64) -> i64 { if kind == CO_WALLCLOCK { return 0 } return 1 } 24 25// are these repeated measurements reproducible (all identical)? the empirical determinism check. 26func co_reproducible(samples: *i64, n: i64) -> i64 { 27 if n <= 1 { return 1 } 28 var i: i64 = 1 29 while i < n { if samples[i] != samples[0] { return 0 } i = i + 1 } 30 return 1 31} 32 33func co_abs(x: i64) -> i64 { if x < 0 { return 0 - x } return x } 34 35// fair performance verdict -- ONLY on a deterministic metric; lower cost wins if the margin clears noise. 36func co_fair_verdict(kind: i64, cost_a: i64, cost_b: i64, margin: i64) -> i64 { 37 if co_metric_deterministic(kind) == 0 { return CO_REJECT } // never judge speed on emulated time 38 if co_abs(cost_a - cost_b) < margin { return CO_TIE } 39 if cost_a < cost_b { return CO_A_FASTER } 40 return CO_B_FASTER 41} 42 43// would judging on wall-clock have FLIPPED across runs? (true bias warning: min/max disagree on winner) 44func co_wallclock_flips(a_samples: *i64, b_samples: *i64, n: i64) -> i64 { 45 var a_ahead: i64 = 0; var b_ahead: i64 = 0; var i: i64 = 0 46 while i < n { 47 if a_samples[i] < b_samples[i] { a_ahead = 1 } 48 if b_samples[i] < a_samples[i] { b_ahead = 1 } 49 i = i + 1 50 } 51 if a_ahead == 1 { if b_ahead == 1 { return 1 } } // both led on some run -> the verdict is noise 52 return 0 53}