From 8531286777aaaf31596012ed924e7f0d6189f8f0 Mon Sep 17 00:00:00 2001
From: Eric Wasylishen <ewasylishen@gmail.com>
Date: Sun, 30 Jan 2022 17:44:48 -0700
Subject: [PATCH] qbsp: replace `-nothreads` with `-threads 1` for consistency
 with light/vis

---
 common/CMakeLists.txt     |  2 +-
 common/threads.cc         | 17 +++++++++++++++++
 include/common/threads.hh | 11 +++++++++++
 include/qbsp/qbsp.hh      |  2 +-
 qbsp/qbsp.cc              | 16 ++++++++--------
 5 files changed, 38 insertions(+), 10 deletions(-)

diff --git a/common/CMakeLists.txt b/common/CMakeLists.txt
index ff161807..90d1a120 100644
--- a/common/CMakeLists.txt
+++ b/common/CMakeLists.txt
@@ -25,4 +25,4 @@ add_library(common STATIC
     ${CMAKE_SOURCE_DIR}/include/common/fs.hh
     ${CMAKE_SOURCE_DIR}/include/common/imglib.hh)
 
-target_link_libraries(common ${CMAKE_THREAD_LIBS_INIT} fmt::fmt nlohmann_json::nlohmann_json)
+target_link_libraries(common ${CMAKE_THREAD_LIBS_INIT} TBB::tbb fmt::fmt nlohmann_json::nlohmann_json)
diff --git a/common/threads.cc b/common/threads.cc
index e8d9a8bb..33df3ba3 100644
--- a/common/threads.cc
+++ b/common/threads.cc
@@ -169,3 +169,20 @@ void RunThreadsOn(int start, int workcnt, void *(func)(void *), void *arg)
 }
 
 #endif /* HAVE_THREADS */
+
+/*
+ * =======================================================================
+ *                                TBB
+ * =======================================================================
+ */
+
+std::unique_ptr<tbb::global_control> ConfigureTBB(int maxthreads)
+{
+    auto tbbOptions = std::unique_ptr<tbb::global_control>();
+
+    if (maxthreads > 0) {
+        tbbOptions = std::make_unique<tbb::global_control>(tbb::global_control::max_allowed_parallelism, maxthreads);
+    }
+
+    return tbbOptions;
+}
diff --git a/include/common/threads.hh b/include/common/threads.hh
index bf94236d..5ef6ffc4 100644
--- a/include/common/threads.hh
+++ b/include/common/threads.hh
@@ -2,6 +2,10 @@
 
 #pragma once
 
+#include <memory>
+
+#include "tbb/global_control.h"
+
 extern int numthreads;
 
 void LowerProcessPriority(void);
@@ -15,3 +19,10 @@ void ThreadUnlock(void);
 
 /* Call if needing to print to stdout - should be called with lock held */
 void InterruptThreadProgress__(void);
+
+/**
+ * Configures TBB to have the given max threads (specify 0 for unlimited).
+ * 
+ * Call this from main() and keep the returned object until main() finishes.
+ */
+std::unique_ptr<tbb::global_control> ConfigureTBB(int maxthreads);
diff --git a/include/qbsp/qbsp.hh b/include/qbsp/qbsp.hh
index edfeb647..d1d00d81 100644
--- a/include/qbsp/qbsp.hh
+++ b/include/qbsp/qbsp.hh
@@ -117,7 +117,7 @@ public:
     bool fLeakTest = false;
     bool fContentHack = false;
     vec_t worldExtent = 0.f;
-    bool fNoThreads = false;
+    int threads = 0; // 0 = let TBB auto select ideal number of threads
     bool includeSkip = false;
     bool fNoTJunc = false;
 };
diff --git a/qbsp/qbsp.cc b/qbsp/qbsp.cc
index 950b520a..9262bdf1 100644
--- a/qbsp/qbsp.cc
+++ b/qbsp/qbsp.cc
@@ -26,6 +26,7 @@
 #include <common/log.hh>
 #include <common/aabb.hh>
 #include <common/fs.hh>
+#include <common/threads.hh>
 #include <qbsp/qbsp.hh>
 #include <qbsp/wad.hh>
 #include <fmt/chrono.h>
@@ -1059,7 +1060,7 @@ PrintOptions
         "   -expand         Write hull 1 expanded brushes to expanded.map for debugging\n"
         "   -leaktest       Make compilation fail if the map leaks\n"
         "   -contenthack    Hack to fix leaks through solids. Causes missing faces in some cases so disabled by default.\n"
-        "   -nothreads      Disable multithreading\n"
+        "   -threads n      Set the number of threads (1 to disable multithreading)\n"
         "   sourcefile      .MAP file to process\n"
         "   destfile        .BSP file to output\n");
 
@@ -1295,8 +1296,11 @@ static void ParseOptions(char *szOptions)
                 options.fLeakTest = true;
             } else if (!Q_strcasecmp(szTok, "contenthack")) {
                 options.fContentHack = true;
-            } else if (!Q_strcasecmp(szTok, "nothreads")) {
-                options.fNoThreads = true;
+            } else if (!Q_strcasecmp(szTok, "threads")) {
+                szTok2 = GetTok(szTok + strlen(szTok) + 1, szEnd);
+                if (!szTok2)
+                    FError("Invalid argument to option {}", szTok);
+                options.threads = atoi(szTok2);
             } else if (!Q_strcasecmp(szTok, "?") || !Q_strcasecmp(szTok, "help")) {
                 PrintOptions();
             } else {
@@ -1421,11 +1425,7 @@ int qbsp_main(int argc, const char **argv)
 
     InitQBSP(argc, argv);
 
-    // disable TBB if requested
-    auto tbbOptions = std::unique_ptr<tbb::global_control>();
-    if (options.fNoThreads) {
-        tbbOptions = std::make_unique<tbb::global_control>(tbb::global_control::max_allowed_parallelism, 1);
-    }
+    auto tbbOptions = ConfigureTBB(options.threads);
 
     // do it!
     auto start = I_FloatTime();