cpuTime: Updated to use the POSIX clock() function

which provides better resolution of the CPU time than times function used
previously.  This will be needed for load-balancing chemistry, Lagrangian
etc. for which the CPU time spent per cell is required.

src/OSspecific/POSIX/cpuTime/cpuTime.C

@@ -2,7 +2,7 @@
   =========                 |
   \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
    \\    /   O peration     | Website:  https://openfoam.org
-    \\  /    A nd           | Copyright (C) 2011-2018 OpenFOAM Foundation
+    \\  /    A nd           | Copyright (C) 2011-2022 OpenFOAM Foundation
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
 License
@@ -24,58 +24,44 @@ License
 \*---------------------------------------------------------------------------*/
 
 #include "cpuTime.H"
-#include <unistd.h>
-
-// * * * * * * * * * * * * * * * Static Members  * * * * * * * * * * * * * * //
-
-const long Foam::cpuTime::Hz_(sysconf(_SC_CLK_TCK));
-
 
 // * * * * * * * * * * * * * Private Member Functions  * * * * * * * * * * * //
 
-void Foam::cpuTime::getTime(timeType& t)
+inline double Foam::cpuTime::timeDifference
+(
+    const clock_t prev,
+    const clock_t cur
+) const
 {
-    times(&t);
-}
-
-
-double Foam::cpuTime::timeDifference(const timeType& beg, const timeType& end)
-{
-    return
-    (
-        double
-        (
-            (end.tms_utime + end.tms_stime)
-          - (beg.tms_utime + beg.tms_stime)
-        )/Hz_
-    );
+    return double(cur - prev)/CLOCKS_PER_SEC;
 }
 
 
 // * * * * * * * * * * * * * * * * Constructors  * * * * * * * * * * * * * * //
 
 Foam::cpuTime::cpuTime()
-{
-    getTime(startTime_);
-    lastTime_ = startTime_;
-    newTime_ = startTime_;
-}
+:
+    startTime_(clock()),
+    prevTime_(startTime_),
+    curTime_(startTime_)
+
+{}
 
 
 // * * * * * * * * * * * * * * * Member Functions  * * * * * * * * * * * * * //
 
 double Foam::cpuTime::elapsedCpuTime() const
 {
-    getTime(newTime_);
-    return timeDifference(startTime_, newTime_);
+    curTime_ = clock();
+    return timeDifference(startTime_, curTime_);
 }
 
 
 double Foam::cpuTime::cpuTimeIncrement() const
 {
-    lastTime_ = newTime_;
-    getTime(newTime_);
-    return timeDifference(lastTime_, newTime_);
+    prevTime_ = curTime_;
+    curTime_ = clock();
+    return timeDifference(prevTime_, curTime_);
 }
 
 

src/OSspecific/POSIX/cpuTime/cpuTime.H

@@ -2,7 +2,7 @@
   =========                 |
   \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
    \\    /   O peration     | Website:  https://openfoam.org
-    \\  /    A nd           | Copyright (C) 2011-2019 OpenFOAM Foundation
+    \\  /    A nd           | Copyright (C) 2011-2022 OpenFOAM Foundation
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
 License
@@ -27,6 +27,9 @@ Class
 Description
     Starts timing CPU usage and return elapsed time from start.
 
+    Uses the POSIX clock() function which return the processor time consumed
+    in clock ticks @ CLOCKS_PER_SEC clock ticks per second.
+
 See also
     clockTime
 
@@ -39,7 +42,6 @@ SourceFiles
 #define cpuTime_H
 
 #include <time.h>
-#include <sys/times.h>
 
 // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
@@ -54,24 +56,25 @@ class cpuTime
 {
     // Private Data
 
-        //- Time structure used
-        typedef struct tms timeType;
+        //- Start CPU clock tick count
+        clock_t startTime_;
 
-        //- Clock-ticks per second
-        static const long Hz_;
+        //- Previous CPU clock tick count
+        mutable clock_t prevTime_;
+
+        //- Current CPU clock tick count
+        mutable clock_t curTime_;
 
-        //- The start time
-        timeType startTime_;
-        mutable timeType lastTime_;
-        mutable timeType newTime_;
 
     // Private Member Functions
 
-        //- Retrieve the current time values from the system
-        static void getTime(timeType&);
-
-        //- Difference between two times
-        static double timeDifference(const timeType& beg, const timeType& end);
+        //- Return the difference between two times clock tick counts
+        //  as elapsed CPU time (in seconds)
+        inline double timeDifference
+        (
+            const clock_t prev,
+            const clock_t cur
+        ) const;
 
 
 public: