Support reverse log in keras embedder and small edge case fix in core…

… converter.

PiperOrigin-RevId: 591905595

vizier/pyvizier/converters/core.py

@@ -451,20 +451,20 @@ def forward_fn(y):
  denom = (high - low) or 1.0
  if denom < 1e-6:
  logging.warning('Unusually small range detected for %s', spec)
- scale_fn = lambda x, high=high, low=low: (np.log(x) - low) / (high - low)
- unscale_fn = lambda x, high=high, low=low: np.exp(x * (high - low) + low)
+ scale_fn = lambda x, low=low, denom=denom: (np.log(x) - low) / denom
+ unscale_fn = lambda x, low=low, denom=denom: np.exp(x * denom + low)
  elif spec.scale == pyvizier.ScaleType.REVERSE_LOG:
- original_sum = low + high
+ raw_sum = low + high
  low, high = np.log(low), np.log(high)
  denom = (high - low) or 1.0
  if denom < 1e-6:
  logging.warning('Unusually small range detected for %s', spec)
 
- def scale_fn(x, high=high, low=low, original_sum=original_sum):
- return 1.0 - (np.log(original_sum - x) - low) / (high - low)
+ def scale_fn(x, low=low, raw_sum=raw_sum, denom=denom):
+ return 1.0 - (np.log(raw_sum - x) - low) / denom
 
- def unscale_fn(x, high=high, low=low, original_sum=original_sum):
- return original_sum - np.exp(high - (high - low) * x)
+ def unscale_fn(x, high=high, raw_sum=raw_sum):
+ return raw_sum - np.exp(high - denom * x)
 
  else:
  if not (spec.scale == pyvizier.ScaleType.LINEAR or spec.scale is None):