--- /dev/null
+// Special g++ Options: -O2
+
+/* KAI's version of Stepanov Benchmark -- Version 1.2
+
+ Version 1.2 -- removed some special code for GNU systems that
+ GNU complained about without -O
+
+To verify how efficiently C++ (and in particular STL) is compiled by
+the present day compilers, I composed a little benchmark. It outputs
+13 numbers. In the ideal world these numbers should be the same. In
+the real world, however, ...
+
+The final number printed by the benchmark is a geometric mean of the
+performance degradation factors of individual tests. It claims to
+represent the factor by which you will be punished by your
+compiler if you attempt to use C++ data abstraction features. I call
+this number "Abstraction Penalty."
+
+As with any benchmark it is hard to prove such a claim; some people
+told me that it does not represent typical C++ usage. It is, however,
+a noteworthy fact that majority of the people who so object are
+responsible for C++ compilers with disproportionatly large Abstraction
+Penalty.
+
+The structure of the benchmark is really quite simple. It adds 2000
+doubles in an array 25000 times. It does it in 13 different ways that
+introduce more and more abstract ways of doing it:
+
+0 - uses simple Fortran-like for loop.
+1 - 12 use STL style accumulate template function with plus function object.
+1, 3, 5, 7 ,9, 11 use doubles.
+2, 4, 6, 8, 10, 12 use Double - double wrapped in a class.
+1, 2 - use regular pointers.
+3, 4 - use pointers wrapped in a class.
+5, 6 - use pointers wrapped in a reverse-iterator adaptor.
+7, 8 - use wrapped pointers wrapped in a reverse-iterator adaptor.
+9, 10 - use pointers wrapped in a reverse-iterator adaptor wrapped in a
+ reverse-iterator adaptor.
+11, 12 - use wrapped pointers wrapped in a reverse-iterator adaptor wrapped
+ in a reverse-iterator adaptor.
+
+All the operators on Double and different pointer-like classes are
+declared inline. The only thing that is really measured is the penalty
+for data abstraction. While templates are used, they do not cause any
+performance degradation. They are used only to simplify the code.
+
+Since many of you are interested in the C++ performance issues, I
+decided to post the benchmark here. I would appreciate if you run it
+and (if possible) send me the results indicating what you have
+compiled it with (CPU, clock rate, compiler, optimization level). It
+is self contained and written so that it could be compiled even with
+those compilers that at present cannot compile STL at all.
+
+It takes a fairly long time to run - on a really slow machine it might
+take a full hour. (For those of you who want to run it faster - give
+it a command line argument that specifies the number of
+iterations. The default is 25000, but it gives an accurate predictions
+even with 500 or a thousand.)
+
+
+Alex Stepanov
+stepanov@mti.sgi.com
+
+*/
+
+
+#include <stddef.h>
+#include <stdio.h>
+#include <time.h>
+#include <math.h>
+#include <stdlib.h>
+
+template <class T>
+inline int operator!=(const T& x, const T& y) {
+ return !(x == y);
+}
+
+struct Double {
+ double value;
+ Double() {}
+ Double(const double& x) : value(x) {}
+ operator double() { return value; }
+};
+
+inline Double operator+(const Double& x, const Double& y) {
+ return Double(x.value + y.value);
+}
+
+struct double_pointer {
+ double* current;
+ double_pointer() {}
+ double_pointer(double* x) : current(x) {}
+ double& operator*() const { return *current; }
+ double_pointer& operator++() {
+ ++current;
+ return *this;
+ }
+ double_pointer operator++(int) {
+ double_pointer tmp = *this;
+ ++*this;
+ return tmp;
+ }
+ double_pointer& operator--() {
+ --current;
+ return *this;
+ }
+ double_pointer operator--(int) {
+ double_pointer tmp = *this;
+ --*this;
+ return tmp;
+ }
+};
+
+
+inline int operator==(const double_pointer& x,
+ const double_pointer& y) {
+ return x.current == y.current;
+}
+
+struct Double_pointer {
+ Double* current;
+ Double_pointer() {}
+ Double_pointer(Double* x) : current(x) {}
+ Double& operator*() const { return *current; }
+ Double_pointer& operator++() {
+ ++current;
+ return *this;
+ }
+ Double_pointer operator++(int) {
+ Double_pointer tmp = *this;
+ ++*this;
+ return tmp;
+ }
+ Double_pointer& operator--() {
+ --current;
+ return *this;
+ }
+ Double_pointer operator--(int) {
+ Double_pointer tmp = *this;
+ --*this;
+ return tmp;
+ }
+};
+
+
+inline int operator==(const Double_pointer& x,
+ const Double_pointer& y) {
+ return x.current == y.current;
+}
+
+template <class RandomAccessIterator, class T>
+struct reverse_iterator {
+ RandomAccessIterator current;
+ reverse_iterator(RandomAccessIterator x) : current(x) {}
+ T& operator*() const {
+ RandomAccessIterator tmp = current;
+ return *(--tmp);
+ }
+ reverse_iterator<RandomAccessIterator, T>& operator++() {
+ --current;
+ return *this;
+ }
+ reverse_iterator<RandomAccessIterator, T> operator++(int) {
+ reverse_iterator<RandomAccessIterator, T> tmp = *this;
+ ++*this;
+ return tmp;
+ }
+ reverse_iterator<RandomAccessIterator, T>& operator--() {
+ ++current;
+ return *this;
+ }
+ reverse_iterator<RandomAccessIterator, T> operator--(int) {
+ reverse_iterator<RandomAccessIterator, T> tmp = *this;
+ --*this;
+ return tmp;
+ }
+};
+
+template <class RandomAccessIterator, class T>
+inline int operator==(const reverse_iterator<RandomAccessIterator, T>& x,
+ const reverse_iterator<RandomAccessIterator, T>& y) {
+ return x.current == y.current;
+}
+
+struct {
+ double operator()(const double& x, const double& y) {return x + y; }
+ Double operator()(const Double& x, const Double& y) {return x + y; }
+} plus;
+
+
+template <class Iterator, class Number>
+Number accumulate(Iterator first, Iterator last, Number result) {
+ while (first != last) result = plus(result, *first++);
+ return result;
+}
+
+int iterations = 25000;
+#define SIZE 2000
+
+int current_test = 0;
+
+double result_times[20];
+
+void summarize() {
+ printf("\ntest absolute additions ratio with\n");
+ printf("number time per second test0\n\n");
+ int i;
+ double millions = (double(SIZE) * iterations)/1000000.;
+ for (i = 0; i < current_test; ++i)
+ {
+ printf("%2i %5.2fsec %5.2fM %.2f\n",
+ i,
+ result_times[i],
+ millions/result_times[i],
+ result_times[i]/result_times[0]);
+ // To make the benchmark into a test-case we check that no
+ // version has a severe abstraction penalty. There will always
+ // be measurement errors, and we don't presently avoid all
+ // abstraction penalty. As the compiler improves, 1.2 should
+ // gradually be replaced with a smaller value.
+ if (result_times[i]/result_times[0] > 1.2)
+ abort ();
+ }
+ double gmean_times = 0.;
+ double total_absolute_times = 0.; // sam added 12/05/95
+ double gmean_rate = 0.;
+ double gmean_ratio = 0.;
+ for (i = 0; i < current_test; ++i) {
+ total_absolute_times += result_times[i]; // sam added 12/05/95
+ gmean_times += log(result_times[i]);
+ gmean_rate += log(millions/result_times[i]);
+ gmean_ratio += log(result_times[i]/result_times[0]);
+ }
+ printf("mean: %5.2fsec %5.2fM %.2f\n",
+ exp(gmean_times/current_test),
+ exp(gmean_rate/current_test),
+ exp(gmean_ratio/current_test));
+ printf("\nTotal absolute time: %.2f sec\n", total_absolute_times); // sam added 12/05/95
+ printf("\nAbstraction Penalty: %.2f\n\n", exp(gmean_ratio/current_test));
+}
+
+clock_t start_time, end_time;
+
+inline void start_timer() { start_time = clock(); }
+
+inline double timer() {
+ end_time = clock();
+ return (end_time - start_time)/double(CLOCKS_PER_SEC);
+}
+
+const double init_value = 3.;
+
+
+
+double data[SIZE];
+
+Double Data[SIZE];
+
+inline void check(double result) {
+ if (result != SIZE * init_value) printf("test %i failed\n", current_test);
+}
+
+void test0(double* first, double* last) {
+ start_timer();
+ for(int i = 0; i < iterations; ++i) {
+ double result = 0;
+ for (int n = 0; n < last - first; ++n) result += first[n];
+ check(result);
+ }
+ result_times[current_test++] = timer();
+}
+
+
+template <class Iterator, class T>
+void test(Iterator first, Iterator last, T zero) {
+ int i;
+ start_timer();
+ for(i = 0; i < iterations; ++i)
+ check(double(accumulate(first, last, zero)));
+ result_times[current_test++] = timer();
+}
+
+template <class Iterator, class T>
+void fill(Iterator first, Iterator last, T value) {
+ while (first != last) *first++ = value;
+}
+
+
+double d = 0.;
+Double D = 0.;
+typedef double* dp;
+dp dpb = data;
+dp dpe = data + SIZE;
+typedef Double* Dp;
+Dp Dpb = Data;
+Dp Dpe = Data + SIZE;
+typedef double_pointer dP;
+dP dPb(dpb);
+dP dPe(dpe);
+typedef Double_pointer DP;
+DP DPb(Dpb);
+DP DPe(Dpe);
+typedef reverse_iterator<dp, double> rdp;
+rdp rdpb(dpe);
+rdp rdpe(dpb);
+typedef reverse_iterator<Dp, Double> rDp;
+rDp rDpb(Dpe);
+rDp rDpe(Dpb);
+typedef reverse_iterator<dP, double> rdP;
+rdP rdPb(dPe);
+rdP rdPe(dPb);
+typedef reverse_iterator<DP, Double> rDP;
+rDP rDPb(DPe);
+rDP rDPe(DPb);
+typedef reverse_iterator<rdp, double> rrdp;
+rrdp rrdpb(rdpe);
+rrdp rrdpe(rdpb);
+typedef reverse_iterator<rDp, Double> rrDp;
+rrDp rrDpb(rDpe);
+rrDp rrDpe(rDpb);
+typedef reverse_iterator<rdP, double> rrdP;
+rrdP rrdPb(rdPe);
+rrdP rrdPe(rdPb);
+typedef reverse_iterator<rDP, Double> rrDP;
+rrDP rrDPb(rDPe);
+rrDP rrDPe(rDPb);
+
+int main(int argv, char** argc) {
+ if (argv > 1) iterations = atoi(argc[1]);
+ fill(dpb, dpe, double(init_value));
+ fill(Dpb, Dpe, Double(init_value));
+ test0(dpb, dpe);
+ test(dpb, dpe, d);
+ test(Dpb, Dpe, D);
+ test(dPb, dPe, d);
+ test(DPb, DPe, D);
+ test(rdpb, rdpe, d);
+ test(rDpb, rDpe, D);
+ test(rdPb, rdPe, d);
+ test(rDPb, rDPe, D);
+ test(rrdpb, rrdpe, d);
+ test(rrDpb, rrDpe, D);
+ test(rrdPb, rrdPe, d);
+ test(rrDPb, rrDPe, D);
+ summarize();
+ return 0;
+}
+
+
+
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