reduce input variants to only _used_ input variants

conda_smithy/configure_feedstock.py

@@ -43,6 +43,7 @@
 import conda_build.utils
 import conda_build.variants
 from conda_build import __version__ as conda_build_version
+from conda_build.metadata import MetaData
 from jinja2 import FileSystemLoader
 from jinja2.sandbox import SandboxedEnvironment
 
@@ -89,6 +90,24 @@
     os.environ.get("CONDA_FORGE_PINNING_LIFETIME", 15 * 60)
 )
 
+ALWAYS_KEEP_KEYS = {
+    "zip_keys",
+    "pin_run_as_build",
+    "MACOSX_DEPLOYMENT_TARGET",
+    "MACOSX_SDK_VERSION",
+    "macos_min_version",
+    "macos_machine",
+    "channel_sources",
+    "channel_targets",
+    "docker_image",
+    "build_number_decrement",
+    # The following keys are required for some of our aarch64 builds
+    # Added in https://github.com/conda-forge/conda-forge-pinning-feedstock/pull/180
+    "cdt_arch",
+    "cdt_name",
+    "BUILD",
+}
+
 
 # use lru_cache to avoid repeating warnings endlessly;
 # this keeps track of 10 different messages and then warns again
@@ -601,23 +620,7 @@ def _collapse_subpackage_variants(
     )
 
     # Add in some variables that should always be preserved
-    always_keep_keys = {
-        "zip_keys",
-        "pin_run_as_build",
-        "MACOSX_DEPLOYMENT_TARGET",
-        "MACOSX_SDK_VERSION",
-        "macos_min_version",
-        "macos_machine",
-        "channel_sources",
-        "channel_targets",
-        "docker_image",
-        "build_number_decrement",
-        # The following keys are required for some of our aarch64 builds
-        # Added in https://github.com/conda-forge/conda-forge-pinning-feedstock/pull/180
-        "cdt_arch",
-        "cdt_name",
-        "BUILD",
-    }
+    always_keep_keys = set() | ALWAYS_KEEP_KEYS
 
     if not is_noarch:
         always_keep_keys.add("target_platform")
@@ -878,6 +881,39 @@ def migrate_combined_spec(combined_spec, forge_dir, config, forge_config):
     return combined_spec
 
 
+def reduce_variants(recipe_path, config, input_variants):
+    """Subset of render_recipe to compute reduced variant matrix
+
+    large numbers of unused variants greatly increase render time
+    """
+
+    # from render_recipe
+    with conda_build.render.open_recipe(recipe_path) as recipe:
+        metadata = MetaData(str(recipe), config=config)
+
+    # from distribute_variants
+    # explode variants dict to list of variants
+    variants = initial_variants = conda_build.variants.get_package_variants(
+        metadata, variants=input_variants
+    )
+    logger.debug(f"Starting with {len(initial_variants)} variants")
+    metadata.config.variant = variants[0]
+    metadata.config.variants = variants
+    all_used = metadata.get_used_vars(force_global=True)
+    # trim unused dimensions, these cost a lot in render_recipe!
+    all_used.update(ALWAYS_KEEP_KEYS)
+    all_used.update(
+        {"target_platform", "extend_keys", "ignore_build_only_deps"}
+    )
+    new_input_variants = input_variants.copy()
+    for key, value in input_variants.items():
+        if len(value) > 1 and key not in all_used:
+            logger.debug(f"Trimming unused dimension: {key}")
+            new_input_variants.pop(key)
+    _trim_unused_zip_keys(new_input_variants)
+    return new_input_variants
+
+
 def _conda_build_api_render_for_smithy(
     recipe_path,
     config=None,
@@ -911,6 +947,12 @@ def _conda_build_api_render_for_smithy(
 
     config = get_or_merge_config(config, **kwargs)
 
+    # reduce unused variants first, they get very expensive in render_recipe
+    if variants:
+        variants = reduce_variants(
+            recipe_path, config=config, input_variants=variants
+        )
+
     metadata_tuples = render_recipe(
         recipe_path,
         bypass_env_check=bypass_env_check,
@@ -920,6 +962,7 @@ def _conda_build_api_render_for_smithy(
         permit_unsatisfiable_variants=permit_unsatisfiable_variants,
     )
     output_metas = []
+    # reduce input variant set to those that are actually used
     for meta, download, render_in_env in metadata_tuples:
         if not meta.skip() or not config.trim_skip:
             for od, om in meta.get_output_metadata_set(
@@ -1061,6 +1104,7 @@ def _render_ci_provider(
         # CBC yaml files where variants in the migrators are not in the CBC.
         # Thus we move it out of the way.
         # TODO: upstream this as a flag in conda-build
+        logger.info(f"Getting variants for {platform}-{arch}")
         try:
             _recipe_cbc = os.path.join(
                 forge_dir,

news/1968_input_variants.rst

@@ -0,0 +1,3 @@
+**Fixed:**
+
+* Improved render time for large numbers of variants