SZ3 and EBCC compressor versions that only have absolute error bound

src/climatebenchpress/compressor/compressors/__init__.py

@@ -2,6 +2,7 @@
     "BitRound",
     "BitRoundPco",
     "Ebcc",
+    "EbccAbsOnly",
     "Jpeg2000",
     "SafeguardedBitRoundPco",
     "SafeguardedSperr",
@@ -13,6 +14,7 @@
     "StochRound",
     "StochRoundPco",
     "Sz3",
+    "Sz3AbsOnly",
     "Tthresh",
     "Zfp",
     "ZfpRound",
@@ -21,7 +23,7 @@
 from . import abc as abc
 from .bitround import BitRound
 from .bitround_pco import BitRoundPco
-from .ebcc import Ebcc
+from .ebcc import Ebcc, EbccAbsOnly
 from .jpeg2000 import Jpeg2000
 from .safeguarded import (
     SafeguardedBitRoundPco,
@@ -34,7 +36,7 @@
 from .sperr import Sperr
 from .stochround import StochRound
 from .stochround_pco import StochRoundPco
-from .sz3 import Sz3
+from .sz3 import Sz3, Sz3AbsOnly
 from .tthresh import Tthresh
 from .zfp import Zfp
 from .zfp_round import ZfpRound

src/climatebenchpress/compressor/compressors/ebcc.py

@@ -1,7 +1,8 @@
-__all__ = ["Ebcc"]
+__all__ = ["Ebcc", "EbccAbsOnly"]
 
 import numcodecs.astype
 import numcodecs_wasm_ebcc
+import numpy as np
 from numcodecs_combinators.stack import CodecStack
 
 from .abc import Compressor
@@ -50,3 +51,37 @@ def rel_bound_codec(error_bound, dtype=None, **kwargs):
                 chunk_shape="auto",
             ),
         )
+
+
+class EbccAbsOnly(Compressor):
+    """EBCC compressor but instead of using the internal EBCC relative error bound,
+    it converts the relative error bound to an absolute error bound.."""
+
+    name = "ebcc-abs"
+    description = "EBCC-Abs"
+
+    @staticmethod
+    def abs_bound_codec(error_bound, dtype=None, **kwargs):
+        assert dtype is not None, "dtype must be provided"
+
+        # Ensure that the error bound is representable as a float32.
+        # For numbers smaller than the smallest positive normal float32,
+        # we use the smallest subnormal float32.
+        error_bound = max(
+            np.float32(error_bound), np.finfo(np.float32).smallest_subnormal
+        )
+
+        return CodecStack(
+            # EBCC only supports float32 data
+            numcodecs.astype.AsType(
+                encode_dtype="float32",
+                decode_dtype=dtype.name,
+            ),
+            numcodecs_wasm_ebcc.Ebcc(
+                # reasonable default recommended by Langwen Huang
+                base_cr=100,
+                residual="absolute",
+                error=float(error_bound),
+                chunk_shape="auto",
+            ),
+        )

src/climatebenchpress/compressor/compressors/sz3.py

@@ -1,4 +1,4 @@
-__all__ = ["Sz3"]
+__all__ = ["Sz3", "Sz3AbsOnly"]
 
 import numcodecs_wasm_sz3
 
@@ -22,3 +22,15 @@ def rel_bound_codec(error_bound, **kwargs):
         # based on the range of the input data:
         # https://github.com/szcompressor/SZ3/blob/e8a6b1569067abdd6b7d4276e91eced115be4f14/include/SZ3/utils/Statistic.hpp#L36
         return numcodecs_wasm_sz3.Sz3(eb_mode="rel", eb_rel=error_bound)
+
+
+class Sz3AbsOnly(Compressor):
+    """SZ3 compressor but instead of using the internal SZ3 relative error bound,
+    it converts the relative error bound to an absolute error bound."""
+
+    name = "sz3-abs"
+    description = "SZ3-Abs"
+
+    @staticmethod
+    def abs_bound_codec(error_bound, **kwargs):
+        return numcodecs_wasm_sz3.Sz3(eb_mode="abs", eb_abs=error_bound)