From 4a18d98251d8cba18a674fccd41d7c2fa8012d0d Mon Sep 17 00:00:00 2001
From: Reini Urban <rurban@cpan.org>
Date: Thu, 1 Oct 2020 13:35:16 +0200
Subject: [PATCH] calculate cpu freq

not hardcoded to 3 GHz.
Some code is based on GH #125, but this result is not really good.
On linux I found an easy way.
---
 Platform.cpp  | 57 +++++++++++++++++++++++++++++++++++++++++++++++++++
 Platform.h    |  1 +
 SpeedTest.cpp |  9 +++++---
 main.cpp      |  2 +-
 4 files changed, 65 insertions(+), 4 deletions(-)

diff --git a/Platform.cpp b/Platform.cpp
index 6aab60ed..408303c0 100644
--- a/Platform.cpp
+++ b/Platform.cpp
@@ -39,3 +39,60 @@ void SetAffinity ( int /*cpu*/ )
 }
 
 #endif
+
+
+// From https://encode.su/threads/3389-Code-snippet-to-compute-CPU-frequency
+// Perform CYCLES simple in-order operations
+static unsigned cycles_loop(unsigned cycles)
+{
+    unsigned a = rand(),  b = rand(),  x = rand();
+    for (unsigned i=0; i < cycles/10; i++)
+    {
+        x = (x + a) ^ b;
+        x = (x + a) ^ b;
+        x = (x + a) ^ b;
+        x = (x + a) ^ b;
+        x = (x + a) ^ b;
+    }
+    return x;
+}
+
+#ifdef __linux__
+#include <string>
+#include <iostream>
+#include <fstream>
+#endif
+
+double cpu_freq()
+{
+  const unsigned cycles = 100*1000*1000;
+  unsigned x = cycles_loop(cycles/10);  // warmup
+#ifdef __linux__
+  std::ifstream curfreqfile("/sys/devices/system/cpu/cpu0/cpufreq/scaling_cur_freq");
+  if (curfreqfile.is_open()) {
+    std::string line;
+    getline(curfreqfile, line);
+    long res = strtol(line.c_str(), NULL, 10);
+    curfreqfile.close();
+    fprintf (stderr, "scaling_cpu_freq: %ld\n", res);
+    fflush(NULL);
+    if (res > 1000)
+      return (double) res / 1000000.0; // 1801310, 2452626
+  }
+#endif
+  double result = 3.0;
+  const uint64_t t1 = timer_start();
+  x += cycles_loop(cycles);
+  const uint64_t t2 = timer_end();
+  // constant adjustment factor, when compared to scaling_cur_freq
+  // ADJ = (res / 1000000.0) / (t2-t1)
+  const double ADJ = 236163824.32526;
+  if (x)
+    result = (double) (ADJ / (t2-t1));
+  if (result < 0.001) {
+    fprintf (stderr, "%u pseudo-cycles, %lu time-cycles\n", cycles, (unsigned long)(t2-t1));
+    return 3.0;
+  }
+  return result;
+  //printf("CPU freq %.2f GHz", (cycles/1e9)/(t2-t1));
+}
diff --git a/Platform.h b/Platform.h
index ae5f1491..9d461d39 100644
--- a/Platform.h
+++ b/Platform.h
@@ -4,6 +4,7 @@
 #pragma once
 
 void SetAffinity ( int cpu );
+double cpu_freq();
 
 #ifndef __x86_64__
  #if defined(__x86_64) || defined(_M_AMD64) || defined(_M_X64)
diff --git a/SpeedTest.cpp b/SpeedTest.cpp
index 7f8b138f..ed89ecf0 100644
--- a/SpeedTest.cpp
+++ b/SpeedTest.cpp
@@ -268,6 +268,7 @@ void BulkSpeedTest ( pfHash hash, uint32_t seed )
 
   printf("Bulk speed test - %d-byte keys\n",blocksize);
   double sumbpc = 0.0;
+  double freq = cpu_freq();
 
   volatile double warmup_cycles = SpeedTest(hash,seed,trials,blocksize,0);
 
@@ -277,12 +278,14 @@ void BulkSpeedTest ( pfHash hash, uint32_t seed )
 
     double bestbpc = double(blocksize)/cycles;
 
-    double bestbps = (bestbpc * 3000000000.0 / 1048576.0);
-    printf("Alignment %2d - %6.3f bytes/cycle - %7.2f MiB/sec @ 3 ghz\n",align,bestbpc,bestbps);
+    double bestbps = (bestbpc * freq * 1000000000.0 / 1048576.0);
+    printf("Alignment %2d - %6.3f bytes/cycle - %7.2f MiB/sec @ %0.2f GHz\n",align,bestbpc,bestbps,freq);
     sumbpc += bestbpc;
   }
   sumbpc = sumbpc / 8.0;
-  printf("Average      - %6.3f bytes/cycle - %7.2f MiB/sec @ 3 ghz\n",sumbpc,(sumbpc * 3000000000.0 / 1048576.0));
+    printf("Average      - %6.3f bytes/cycle - %7.2f MiB/sec @ %0.2f GHz\n",sumbpc,
+           (sumbpc * freq * 1000000000.0 / 1048576.0),
+           freq);
   fflush(NULL);
 }
 
diff --git a/main.cpp b/main.cpp
index f742fbf9..4546245f 100644
--- a/main.cpp
+++ b/main.cpp
@@ -631,7 +631,7 @@ void test ( hashfunc<hashtype> hash, HashInfo* info )
       sum += TinySpeedTest(hashfunc<hashtype>(info->hash),sizeof(hashtype),j,info->verification,true);
     }
     g_speed = sum = sum / 31.0;
-    printf("Average                                    %6.3f cycles/hash\n",sum);
+    printf("Average                                  %8.3f cycles/hash\n",sum);
     printf("\n");
     fflush(NULL);
   } else {