Cross-correlation alignment method and docstrings.

src/corrgi/__init__.py

@@ -1,3 +0,0 @@
-from .example_module import greetings, meaning
-
-__all__ = ["greetings", "meaning"]

src/corrgi/alignment.py

@@ -16,7 +16,16 @@
 
 
 def autocorrelation_alignment(catalog: Catalog) -> PixelAlignment:
-    """TODO"""
+    """Determine all pairs of partitions that should be correlated within the same catalog.
+
+    This considers all combinations, without duplicates between the "primary" and "join"
+    pixels in the alignment.
+
+    Args:
+        catalog (Catalog): catalog for autocorrelation
+    Returns:
+        alignment object where the `aligned` columns simply match the left pixel.
+    """
     upper_triangle = [
         [left.order, left.pixel, right.order, right.pixel, left.order, left.pixel]
         for (left, right) in itertools.combinations(catalog.get_healpix_pixels(), 2)
@@ -33,5 +42,21 @@ def autocorrelation_alignment(catalog: Catalog) -> PixelAlignment:
 
 
 def crosscorrelation_alignment(catalog_left: Catalog, catalog_right: Catalog) -> PixelAlignment:
-    """TODO"""
-    pass
+    """Determine all pairs of partitions that should be correlated between two catalogs.
+
+    This considers the full cross-product of pixels.
+
+    Args:
+        catalog_left (Catalog): left side of the cross-correlation
+        catalog_right (Catalog): right side of the cross-correlation
+    Returns:
+        alignment object where the `aligned` columns simply match the left pixel.
+    """
+    full_product = [
+        [left.order, left.pixel, right.order, right.pixel, left.order, left.pixel]
+        for (left, right) in itertools.product(
+            catalog_left.get_healpix_pixels(), catalog_right.get_healpix_pixels()
+        )
+    ]
+    result_mapping = pd.DataFrame(full_product, columns=column_names)
+    return PixelAlignment(catalog_left.pixel_tree, result_mapping, PixelAlignmentType.OUTER)

tests/corrgi/test_alignment.py

@@ -1,8 +1,18 @@
 import hipscat
-from corrgi.alignment import autocorrelation_alignment
+from corrgi.alignment import autocorrelation_alignment, crosscorrelation_alignment
 
 
 def test_autocorrelation_alignment(data_catalog_dir):
     data_catalog = hipscat.read_from_hipscat(data_catalog_dir)
     alignment = autocorrelation_alignment(data_catalog)
     assert len(alignment.pixel_mapping) == 28
+
+
+def test_crosscorrelation_alignment(dr7_lrg_catalog_dir, dr7_lrg_rand_catalog_dir):
+    dr7_catalog = hipscat.read_from_hipscat(dr7_lrg_catalog_dir)
+    dr7_rand_catalog = hipscat.read_from_hipscat(dr7_lrg_rand_catalog_dir)
+    alignment = crosscorrelation_alignment(dr7_catalog, dr7_rand_catalog)
+    ## dr7_catalog has 12 partitions
+    ## dr7_rand_catalog has 22 partitions
+    ## 12*21 = 252
+    assert len(alignment.pixel_mapping) == 252