fix: handle sparse matrix reading for big-endian byte order

src/elisa/data/base.py

@@ -1138,8 +1138,14 @@ def __init__(
         photon_egrid = np.array(photon_egrid, dtype=np.float64, order='C')
         channel_emin = np.array(channel_emin, dtype=np.float64, order='C')
         channel_emax = np.array(channel_emax, dtype=np.float64, order='C')
-        response_matrix = coo_array(response_matrix)
-        response_matrix.eliminate_zeros()
+        # if the byte order is not native,
+        # then convert it to be compatible with scipy.sparse
+        if not isinstance(response_matrix, sparray):
+            if response_matrix.dtype.byteorder != '=':
+                order = response_matrix.dtype.newbyteorder()
+                response_matrix = response_matrix.astype(order)
+            response_matrix = coo_array(response_matrix)
+            response_matrix.eliminate_zeros()
         channel = np.array(channel, dtype=str, order='C')
 
         photon_egrid_shape = np.shape(photon_egrid)

src/elisa/data/ogip.py

@@ -629,6 +629,12 @@ def _read_response(self, file: str, response_id: int) -> dict:
         else:
             reduced_matrix = np.hstack(matrix)
 
+        # if the byte order is not native,
+        # then convert it to be compatible with scipy.sparse
+        if reduced_matrix.dtype.byteorder != '=':
+            order = reduced_matrix.dtype.newbyteorder()
+            reduced_matrix = reduced_matrix.astype(order)
+
         sparse_matrix = coo_array(
             (reduced_matrix, (rows, cols)),
             shape=(len(response_data), channel_number),

tests/test_data.py

@@ -1,6 +1,8 @@
 import numpy as np
+import pytest
 
 from elisa.data.grouping import significance_gv, significance_lima
+from elisa.data.ogip import Response, ResponseData
 from elisa.models import PowerLaw
 
 
@@ -117,3 +119,28 @@ def test_data_grouping():
         data.spec_counts, data.back_counts, data.back_errors, data.back_ratio
     )
     assert np.all(sig >= scale)
+
+
+@pytest.mark.parametrize(
+    'file',
+    [
+        '../docs/notebooks/data/P011160500104_LE.rsp',
+        '../docs/notebooks/data/P011160500104_ME.rsp',
+        '../docs/notebooks/data/P011160500104_HE.rsp',
+    ],
+)
+def test_load_response(file):
+    # Test Response against big-endian files
+    assert np.all(Response(file).channel_fwhm > 0)
+
+
+def test_response():
+    # Test ResponseData against different endianness
+    photon_egrid = np.linspace(1.0, 100.0, 101)
+    channel = np.arange(100)
+    channel_emin = photon_egrid[:-1]
+    channel_emax = photon_egrid[1:]
+    matrix1 = np.eye(100).astype('<f4')
+    matrix2 = np.eye(100).astype('>f4')
+    ResponseData(photon_egrid, channel_emin, channel_emax, matrix1, channel)
+    ResponseData(photon_egrid, channel_emin, channel_emax, matrix2, channel)