From 404f9e9cc9595e5349a9d0941ed6b0d4d339f934 Mon Sep 17 00:00:00 2001
From: Tim Reichelt <treichelt6@gmail.com>
Date: Wed, 27 May 2026 09:25:42 +0100
Subject: [PATCH 1/2] Add SZ3 and EBCC versions that only use absolute error
 bound

---
 .../compressor/compressors/__init__.py        |  6 ++--
 .../compressor/compressors/ebcc.py            | 29 ++++++++++++++++++-
 .../compressor/compressors/sz3.py             | 14 ++++++++-
 3 files changed, 45 insertions(+), 4 deletions(-)

diff --git a/src/climatebenchpress/compressor/compressors/__init__.py b/src/climatebenchpress/compressor/compressors/__init__.py
index 1b87b38..4c58e9f 100644
--- a/src/climatebenchpress/compressor/compressors/__init__.py
+++ b/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
diff --git a/src/climatebenchpress/compressor/compressors/ebcc.py b/src/climatebenchpress/compressor/compressors/ebcc.py
index 9c77e5c..8c82808 100644
--- a/src/climatebenchpress/compressor/compressors/ebcc.py
+++ b/src/climatebenchpress/compressor/compressors/ebcc.py
@@ -1,4 +1,4 @@
-__all__ = ["Ebcc"]
+__all__ = ["Ebcc", "EbccAbsOnly"]
 
 import numcodecs.astype
 import numcodecs_wasm_ebcc
@@ -50,3 +50,30 @@ 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"
+
+        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=error_bound,
+                chunk_shape="auto",
+            ),
+        )
diff --git a/src/climatebenchpress/compressor/compressors/sz3.py b/src/climatebenchpress/compressor/compressors/sz3.py
index 6d00300..4dcb9f2 100644
--- a/src/climatebenchpress/compressor/compressors/sz3.py
+++ b/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)

From 9f5426eaa10877d5ab1e3b3330f20f5683edce5b Mon Sep 17 00:00:00 2001
From: Tim Reichelt <treichelt6@gmail.com>
Date: Thu, 28 May 2026 12:19:59 +0100
Subject: [PATCH 2/2] Ensure that EBCC error bound is positive

---
 src/climatebenchpress/compressor/compressors/ebcc.py | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/src/climatebenchpress/compressor/compressors/ebcc.py b/src/climatebenchpress/compressor/compressors/ebcc.py
index 8c82808..72f5e2c 100644
--- a/src/climatebenchpress/compressor/compressors/ebcc.py
+++ b/src/climatebenchpress/compressor/compressors/ebcc.py
@@ -2,6 +2,7 @@
 
 import numcodecs.astype
 import numcodecs_wasm_ebcc
+import numpy as np
 from numcodecs_combinators.stack import CodecStack
 
 from .abc import Compressor
@@ -63,6 +64,13 @@ class EbccAbsOnly(Compressor):
     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(
@@ -73,7 +81,7 @@ def abs_bound_codec(error_bound, dtype=None, **kwargs):
                 # reasonable default recommended by Langwen Huang
                 base_cr=100,
                 residual="absolute",
-                error=error_bound,
+                error=float(error_bound),
                 chunk_shape="auto",
             ),
         )