kDefaultBackendTolerance top-level constant
double
const kDefaultBackendTolerance
Default tolerance: 1% of the reference output's range.
Measured separation on macOS arm64 across five shipping models is wide enough that this is not a tuned knob. Healthy configurations deviated by at most 0.068% (including fp16 on GPU), while known-corrupt ones deviated by 42% or more. 1% sits roughly 15x above the worst honest result and 40x below the mildest corruption.
Implementation
const double kDefaultBackendTolerance = 0.01;