[GitHub] [datasketches-cpp] jmalkin commented on a diff in pull request #325: Cpp countmin

["jmalkin (via GitHub)" <gi...@apache.org>]

jmalkin commented on code in PR #325:
URL: https://github.com/apache/datasketches-cpp/pull/325#discussion_r1122238713


##########
count/include/count_min_impl.hpp:
##########
@@ -0,0 +1,322 @@
+#ifndef COUNT_MIN_IMPL_HPP_
+#define COUNT_MIN_IMPL_HPP_
+
+#include "MurmurHash3.h"
+#include <random>
+
+namespace datasketches {
+
+template<typename W>
+count_min_sketch<W>::count_min_sketch(uint8_t num_hashes, uint32_t num_buckets, uint64_t seed):
+_num_hashes(num_hashes),
+_num_buckets(num_buckets),
+_sketch_array(num_hashes * num_buckets, 0),

Review Comment:
   This will attempt to initialize a gigantic array, only to later decide that it's too big and throw an exception. We can instead do an initial check here:
   `_sketch_array((num_hashes*num_buckets < 1<<30) ? num_hashes*num_buckets : 0, 0),`
   which should let us re-enabld the unit test check and also avoid a potential overallocaiton issue for end-users.



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