CHOLMOD METIS interface: use GKRAND with threadprivate

CHOLMOD/CMakeLists.txt

@@ -380,6 +380,11 @@ if ( OPENMP_FOUND )
     set ( CMAKE_C_FLAGS   "${CMAKE_C_FLAGS}   ${OpenMP_C_FLAGS} " )
     set ( CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} ${OpenMP_C_FLAGS} " )
     include_directories ( ${OpenMP_C_INCLUDE_DIRS} )
+else ( )
+    # to fix METIS: use threadprivate variables for GKRAND instead globals,
+    # so multiple user threads can call cholmod_analyze in parallel on
+    # different matrices, and avoid global locking of the system rand.
+    include ( SuiteSparse__thread )
 endif ( )
 
 # libm:

CHOLMOD/Doc/CHOLMOD_UserGuide.tex

@@ -48,7 +48,7 @@
 \end{abstract}
 %-------------------------------------------------------------------------------
 
-CHOLMOD Copyright\copyright 2005-2022 by Timothy A. Davis, All Rights Reserved.
+CHOLMOD Copyright\copyright 2005-2023 by Timothy A. Davis, All Rights Reserved.
 Portions are also copyrighted by William W. Hager (the {\tt Modify} Module),
 and the University of Florida (the {\tt Partition} and {\tt Core} Modules).
 All Rights Reserved.

CHOLMOD/Doc/ChangeLog

@@ -6,6 +6,8 @@ FIXME DATE, 2023: version 4.2.0
         cholmod_metis_wrapper.c, Tcov/memory.c.
     * support for SPQR: minor changes to support SPQR v4.2.0 with 32-bit
         integers; no change to user-visible API.
+    * METIS now using GKRAND: with threadprivate state variables, to
+        avoid global system lock when using CHOLMON on many user threads
 
 June 16, 2023: version 4.0.4
 

CHOLMOD/Partition/cholmod_metis_wrapper.h

@@ -2,7 +2,7 @@
 // CHOLMOD/Partition/cholmod_metis_wrapper.h: METIS renaming for CHOLMOD
 //------------------------------------------------------------------------------
 
-// CHOLMOD/Partition Module.  Copyright (C) 2005-2022, University of Florida.
+// CHOLMOD/Partition Module.  Copyright (C) 2005-2023, University of Florida.
 // All Rights Reserved.  Author: Timothy A. Davis.
 // SPDX-License-Identifier: LGPL-2.1+
 
@@ -11,6 +11,11 @@
 #ifndef CHOLMOD_METIS_WRAP_H
 #define CHOLMOD_METIS_WRAP_H
 
+// always use GKRAND instead of the system rand in METIS
+#ifndef USE_GKRAND
+#define USE_GKRAND
+#endif
+
 #if defined ( __GNUC__ ) && !defined ( __clang__ )
     // disable memcpy warnings:
     #pragma GCC diagnostic ignored "-Wstringop-overflow="

CHOLMOD/SuiteSparse_metis/GKlib/random.c

@@ -60,11 +60,41 @@ GK_MKRANDOM(gk_z,   size_t, ssize_t)
 #define UM 0xFFFFFFFF80000000ULL /* Most significant 33 bits */
 #define LM 0x7FFFFFFFULL /* Least significant 31 bits */
 
+// added by Tim Davis for CHOLMOD: mt and mti state variables threadprivate
+#if defined ( _OPENMP )
 
+    // OpenMP threadprivate is preferred
+    static uint64_t mt[NN];
+    static int mti=NN+1;
+    #pragma omp threadprivate (mt,mti)
+
+#elif defined ( HAVE_KEYWORD__THREAD )
+
+    // gcc and many other compilers support the __thread keyword
+    __thread static uint64_t mt[NN];
+    __thread static int mti=NN+1;
+
+#elif defined ( HAVE_KEYWORD__DECLSPEC_THREAD )
+
+    // Windows: __declspec (thread)
+    __declspec ( thread ) static uint64_t mt[NN];
+    __declspec ( thread ) static int mti=NN+1;
+
+#elif defined ( HAVE_KEYWORD__THREAD_LOCAL )
+
+    // ANSI C11 threads
+    #include <threads.h>
+    _Thread_local static uint64_t mt[NN];
+    _Thread_local static int mti=NN+1;
+
+#else
+// original METIS uses global state: this is not thread-safe:
 /* The array for the state vector */
 static uint64_t mt[NN]; 
 /* mti==NN+1 means mt[NN] is not initialized */
 static int mti=NN+1; 
+#endif
+
 #endif /* USE_GKRAND */
 
 /* initializes mt[NN] with a seed */

Makefile

@@ -183,7 +183,7 @@ demos:
 # Create the PDF documentation
 docs:
 	( cd GraphBLAS && $(MAKE) docs )
-	( cd Mongoose  && $(MAKE) docs )
+	# ( cd Mongoose  && $(MAKE) docs )
 	( cd AMD && $(MAKE) docs )
 	( cd CAMD && $(MAKE) docs )
 	( cd KLU && $(MAKE) docs )

SuiteSparse_config/SuiteSparse__thread.cmake

@@ -0,0 +1,72 @@
+#-------------------------------------------------------------------------------
+# GraphBLAS/cmake_modules/SuiteSparse__thread.cmake
+#-------------------------------------------------------------------------------
+
+# Copyright (c) 2017-2023, Timothy A. Davis.  All Rights Reserved.
+# SPDX-License-Identifier: Apache-2.0
+
+#-------------------------------------------------------------------------------
+
+# determine if the __thread keyword is available, which is an extension by
+# gcc but supported by many compilers, to indicate thread-local-storage.
+
+include ( CheckCSourceRuns )
+
+set ( thread_src
+"   #include <stdio.h>
+    __thread int x = 1 ;
+    int main (void)
+    {
+        x = 0 ;
+        return (x) ;
+    }
+" )
+
+set ( declspec_thread_src
+"   #include <stdio.h>
+    __declspec ( thread ) int x = 1 ;
+    int main (void)
+    {
+        x = 0 ;
+        return (x) ;
+    }
+" )
+
+set ( thread_local_src
+"   #include <stdio.h>
+    #include <threads.h>
+    _Thread_local int x = 1 ;
+    int main (void)
+    {
+        x = 0 ;
+        return (x) ;
+    }
+" )
+
+check_c_source_runs ( "${declspec_thread_src}" HAVE_KEYWORD__DECLSPEC_THREAD )
+
+check_c_source_runs ( "${thread_src}" HAVE_KEYWORD__THREAD )
+
+check_c_source_runs ( "${thread_local_src}" HAVE_KEYWORD__THREAD_LOCAL )
+
+if ( HAVE_KEYWORD__DECLSPEC_THREAD )
+    add_compile_definitions ( HAVE_KEYWORD__DECLSPEC_THREAD )
+    message ( STATUS "__declspec(thread) keyword: available" )
+else ( )
+    message ( STATUS "__declspec(thread) keyword: not available" )
+endif ( )
+
+if ( HAVE_KEYWORD__THREAD )
+    add_compile_definitions ( HAVE_KEYWORD__THREAD )
+    message ( STATUS "__thread keyword: available" )
+else ( )
+    message ( STATUS "__thread keyword: not available" )
+endif ( )
+
+if ( HAVE_KEYWORD__THREAD_LOCAL )
+    add_compile_definitions ( HAVE_KEYWORD__THREAD_LOCAL )
+    message ( STATUS "_Thread_local keyword: available" )
+else ( )
+    message ( STATUS "_Thread_local_thread keyword: not available" )
+endif ( )
+