Sanitize the number of threads when parallelizing the count.

This avoids overallocation when too many threads are specified, and avoids real
problems when a user specifies a non-positive number of threads. This now
requires a direct (instead of transitive) dependency on subpar.

CMakeLists.txt

@@ -15,9 +15,10 @@ if(TATAMI_STATS_FETCH_EXTERN)
     add_subdirectory(extern)
 else()
     find_package(tatami_tatami 3.0.0 CONFIG REQUIRED)
+    find_package(ltla_subpar 0.3.0 CONFIG REQUIRED)
 endif()
 
-target_link_libraries(tatami_stats INTERFACE tatami::tatami)
+target_link_libraries(tatami_stats INTERFACE tatami::tatami ltla::subpar)
 
 include(GNUInstallDirs)
 target_include_directories(tatami_stats INTERFACE 

cmake/Config.cmake.in

@@ -2,5 +2,6 @@
 
 include(CMakeFindDependencyMacro)
 find_dependency(tatami_tatami 3.0.0 CONFIG REQUIRED)
+find_dependency(ltla_subpar 0.3.0 CONFIG REQUIRED)
 
 include("${CMAKE_CURRENT_LIST_DIR}/tatami_tatami_statsTargets.cmake")

extern/CMakeLists.txt

@@ -3,8 +3,14 @@ include(FetchContent)
 FetchContent_Declare(
   tatami
   GIT_REPOSITORY https://github.com/tatami-inc/tatami
-  GIT_TAG master # ^v3.0.0
+  GIT_TAG master # ^3.0.0
 )
 
-FetchContent_MakeAvailable(tatami)
+FetchContent_Declare(
+  subpar
+  GIT_REPOSITORY https://github.com/LTLA/subpar
+  GIT_TAG master # ^0.3.0
+)
 
+FetchContent_MakeAvailable(tatami)
+FetchContent_MakeAvailable(subpar)

include/tatami_stats/counts.hpp

@@ -86,6 +86,7 @@ void apply(bool row, const tatami::Matrix<Value_, Index_>* p, Output_* output, i
         }
 
     } else {
+        num_threads = subpar::sanitize_num_workers(num_threads, otherdim); // provides some protection against silly num_threads iputs.
         std::vector<Output_*> threaded_output_ptrs(num_threads, output);
         std::vector<std::vector<Output_> > threaded_output(num_threads - 1);
         for (int t = 1; t < num_threads; ++t) {