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-rw-r--r--graphics/asymptote/parallel.cc74
1 files changed, 74 insertions, 0 deletions
diff --git a/graphics/asymptote/parallel.cc b/graphics/asymptote/parallel.cc
new file mode 100644
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+++ b/graphics/asymptote/parallel.cc
@@ -0,0 +1,74 @@
+#include <iostream>
+#include <cstdlib>
+#include <cstdint>
+
+#include "parallel.h"
+
+#ifndef __Complex_h__
+#include <complex>
+typedef std::complex<double> Complex;
+#endif
+
+#include "statistics.h"
+#include "align.h"
+#include <chrono>
+
+namespace utils {
+int ALIGNMENT=2*sizeof(Complex); // Must be a multiple of sizeof(Complex)
+}
+
+using namespace utils;
+
+size_t threshold=SIZE_MAX;
+
+namespace parallel {
+
+size_t lastThreads=SIZE_MAX;
+
+const size_t maxThreshold=1 << 24;
+
+size_t parallelLoop(Complex *A, size_t m, size_t threads)
+{
+ auto T0=std::chrono::steady_clock::now();
+ PARALLEL(
+ for(size_t k=0; k < m; ++k)
+ A[k]=k;
+ );
+ PARALLEL(
+ for(size_t k=0; k < m; ++k)
+ A[k] *= k;
+ );
+ auto T1=std::chrono::steady_clock::now();
+
+ auto elapsed=std::chrono::duration_cast<std::chrono::nanoseconds>
+ (T1-T0);
+ return elapsed.count();
+}
+
+size_t measureThreshold(size_t threads)
+{
+ if(threads > 1) {
+ for(size_t m=1; m < maxThreshold; m *= 2) {
+ Complex *A=ComplexAlign(m);
+ if(!A)
+ break;
+ if(parallelLoop(A,m,threads) < parallelLoop(A,m,1))
+ return m;
+ deleteAlign(A);
+ }
+ }
+ return maxThreshold;
+}
+
+void Threshold(size_t threads)
+{
+ if(threads > 1 && threads < lastThreads) {
+ statistics S(true);
+ for(size_t i=0; i < 10; ++i)
+ S.add(measureThreshold(threads));
+ threshold=S.median();
+ lastThreads=threads;
+ }
+}
+
+}