diff --git a/lab_2/11/Makefile b/lab_2/11/Makefile
new file mode 100644
index 0000000..0ef13b8
--- /dev/null
+++ b/lab_2/11/Makefile
@@ -0,0 +1,18 @@
+binary = memleak
+folder = memleak
+objects = $(patsubst %.cpp,%.o,$(wildcard *.cpp))
+
+run: $(binary)
+	./$(binary) 7 100000000
+
+$(binary): $(objects)
+	g++ -o $@ $^
+
+clean:
+	rm -f *.o
+
+clear: clean
+	rm -f *.zip $(binary)
+
+zip: clean
+	zip $(folder) Makefile *.cpp *.h
diff --git a/lab_2/11/chain-random-walk.cpp b/lab_2/11/chain-random-walk.cpp
new file mode 100644
index 0000000..780b048
--- /dev/null
+++ b/lab_2/11/chain-random-walk.cpp
@@ -0,0 +1,78 @@
+#include <cstdlib>
+#include <iomanip>
+#include <iostream>
+
+#include "chain-random-walk.h"
+
+using namespace crw;
+
+namespace {
+   // set each element forward or backward by 1, at random
+   void stochastic_unit_step(long size, float config[])
+   {
+      for(long i = 0; i < size; i++)
+         if(std::rand() % 2 == 0) config[i]++;
+         else config[i]--;
+   }
+   
+   void shift_centre_to_origin(long size, float config[])
+   {
+       double sum = 0.0;
+       for(long i = 0; i < size; i++) sum += config[i];
+       for(long i = 0; i < size; i++) config[i] -= sum/size;
+   }
+   
+   const int el_out_max = 9;  // show at most the first nine elements
+}
+
+float crw::elongation(long size, float config[])
+{
+   float min = config[0];
+   float max = config[0];
+   
+   for(long i = 1; i < size; i++)
+      if(config[i] > max) max = config[i];
+      else if(config[i] < min) min = config[i];
+
+   return max - min;
+}
+
+float* crw::step(long size, float previous[])
+{
+   // allocate the next configuration
+   float* config = new float[size]();
+    
+   // first, let the chain contract: each element is attracted by its neighbours
+   for(long i = 0; i < size; i++)
+      config[i] = 0.5*previous[i] + 0.25*previous[(i-1) % size]
+                                  + 0.25*previous[(i+1) % size];
+
+   stochastic_unit_step(size, config);  // actual random walk step
+   shift_centre_to_origin(size, config);  // shift such that the average remains zero
+
+   return config;
+}
+
+void crw::output(long no, long size, float present[], float extreme[], double avg_el)
+{
+   /* output statistics over the run so far 
+    */
+   std::cout << std::setw(12) << no << "\t" << std::setprecision(3) << std::fixed
+             << std::setw(6) << elongation(size, present) << " "
+             << std::setprecision(7) << std::setw(10) << avg_el << " " << std::setprecision(5) 
+             << std::setw(9) << elongation(size, extreme) << std::setprecision(3) << "\t\t";
+   
+   /* display the present configuration, showing up to <el_out_max> element coordinates */
+   for(long i = 0; (i < size) && (i < el_out_max); i++)
+       std::cout << std::setw(7) << present[i] << " ";
+   if(size > el_out_max) std::cout << "...";
+   std::cout << "\t\t";
+    
+   /* display the most extreme configuration so far,
+    * showing up to <el_out_max> element coordinates
+    */
+   for(long i = 0; (i < size) && (i < el_out_max); i++)
+       std::cout << std::setw(7) << extreme[i] << " ";
+   if(size > el_out_max) std::cout << "...";
+   std::cout << "\n";
+}
diff --git a/lab_2/11/chain-random-walk.h b/lab_2/11/chain-random-walk.h
new file mode 100644
index 0000000..9ad3d0e
--- /dev/null
+++ b/lab_2/11/chain-random-walk.h
@@ -0,0 +1,11 @@
+#ifndef CHAIN_RANDOM_WALK_H
+#define CHAIN_RANDOM_WALK_H
+
+namespace crw
+{
+   float elongation(long size, float config[]);
+   float* step(long size, float previous[]);
+   void output(long no, long size, float present[], float extreme[], double avg_el);
+}
+
+#endif
diff --git a/lab_2/11/const_Nm_timings.csv b/lab_2/11/const_Nm_timings.csv
new file mode 100644
index 0000000..9380c34
--- /dev/null
+++ b/lab_2/11/const_Nm_timings.csv
@@ -0,0 +1,10 @@
+1024, 40.45
+512, 41.08
+256, 41.65
+128, 43.26
+64, 43.98
+32, 46.27
+16, 49.63
+8, 51.05
+4, 48.74
+2, 55.97
diff --git a/lab_2/11/const_m_timings.csv b/lab_2/11/const_m_timings.csv
new file mode 100644
index 0000000..621bc60
--- /dev/null
+++ b/lab_2/11/const_m_timings.csv
@@ -0,0 +1,10 @@
+1024, 40.51
+512, 20.54
+256, 10.54
+128, 5.35
+64, 2.78
+32, 1.47
+16, 0.79
+8, 0.41
+4, 0.20
+2, 0.11
diff --git a/lab_2/11/log.csv b/lab_2/11/log.csv
new file mode 100644
index 0000000..ec7ad70
--- /dev/null
+++ b/lab_2/11/log.csv
@@ -0,0 +1,10 @@
+1024, 42.77
+512, 21.70
+256, 10.86
+128, 5.67
+64, 2.88
+32, 1.53
+16, 0.84
+8, 0.45
+4, 0.21
+2, 0.11
\ No newline at end of file
diff --git a/lab_2/11/memleak.cpp b/lab_2/11/memleak.cpp
new file mode 100644
index 0000000..5833225
--- /dev/null
+++ b/lab_2/11/memleak.cpp
@@ -0,0 +1,66 @@
+#include <cassert>
+#include <cstdlib>
+#include <ctime>
+
+#include "chain-random-walk.h"
+
+namespace {
+   constexpr int default_size = 7;
+   constexpr int default_steps = 100000000;
+   constexpr int outlines = 25;
+}
+
+/* first argument: array size
+ * second argument: number of steps
+ */
+int main(int argc, char** argv)
+{
+   long size = default_size;
+   if(argc > 1) size = std::atol(argv[1]);
+   assert(size > 0);
+    
+   long steps = default_steps;
+   if(argc > 2) steps = std::atol(argv[2]);
+   assert(steps > 0);
+    
+   long outfreq = steps / outlines;
+   if(outfreq < 1) outfreq = 1;
+    
+   /* the configuration is given by an array of float numbers */
+   float* present_configuration = new float[size]();
+
+   /* store the one with greatest deviation between min and max element */
+   float* extreme_configuration = present_configuration;
+   float extreme_elongation = 0.0;
+   double el_sum = 0.0;
+   double el_avg = 0.0;
+
+   std::srand(std::time(nullptr)); // initialize the random number generator
+   
+   for(long i = 0; i < steps; i++)
+   {
+      if(i % outfreq == 0)
+         crw::output(i, size, present_configuration, extreme_configuration, el_avg);
+      
+      /* here we are calling the random walk step;
+       * this returns a new configuration (float array) on the heap
+       */
+
+      // Simple fix to memleak:
+      float* old_configuration = present_configuration;
+      present_configuration = crw::step(size, present_configuration);
+      delete old_configuration;
+      float present_elongation = crw::elongation(size, present_configuration);
+
+      if(present_elongation > extreme_elongation)
+      {
+          extreme_configuration = present_configuration;
+          extreme_elongation = present_elongation;
+      }
+      el_sum += present_elongation;
+      el_avg = el_sum / (i + 1.0);
+   }
+   crw::output(steps, size, present_configuration, extreme_configuration, el_avg);
+
+   delete[] present_configuration;
+}
diff --git a/lab_2/11/plot_speedup.py b/lab_2/11/plot_speedup.py
new file mode 100644
index 0000000..4417be1
--- /dev/null
+++ b/lab_2/11/plot_speedup.py
@@ -0,0 +1,38 @@
+import matplotlib.pyplot as plt
+import matplotlib.cbook as cbook
+
+import numpy as np
+import pandas as pd
+
+f1 = open('const_m_timings.csv', 'r')
+f2 = open('../10_memleak/const_m_timings.csv', 'r')
+x1 = []
+y1 = []
+for l,p in zip(f1.readlines(), f2.readlines()):
+    l = l.split(',')
+    p = p.split(',')
+    x1.append(p[0])
+    y1.append(float(p[1])/float(l[1]))
+
+f1 = open('const_Nm_timings.csv', 'r')
+f2 = open('../10_memleak/const_Nm_timings.csv', 'r')
+x2 = []
+y2 = []
+for l,p in zip(f1.readlines(), f2.readlines()):
+    l = l.split(',')
+    p = p.split(',')
+    x2.append(p[0])
+    y2.append(float(p[1])/float(l[1]))
+
+plt.plot(x1, y1, label = 'constant m')
+plt.plot(x2, y2, label = 'constant Nm')
+for i in range(len(x1)):
+        plt.text(i,y1[i],f'{y1[i]:.2f}', color="blue")
+for i in range(len(x2)):
+        plt.text(i,y2[i],f'{y2[i]:.2f}', color="orange")
+plt.title('Speedup after fixing leak')
+plt.xlabel('N')
+plt.ylabel('xspeedup')
+plt.grid()
+plt.legend()
+plt.show()
diff --git a/lab_2/11/time_N.nu b/lab_2/11/time_N.nu
new file mode 100644
index 0000000..cfa51f1
--- /dev/null
+++ b/lab_2/11/time_N.nu
@@ -0,0 +1,7 @@
+for x in [1024 512 256 128 64 32 16 8 4 2] {
+let filename = 'const_m_timings.csv';
+$x | into string | save --append $filename;
+", " | save --append $filename;
+let m = 2000000;
+time -f %e -a -o  $filename ./memleak $x $m;
+};
\ No newline at end of file
diff --git a/lab_2/11/time_Nm.nu b/lab_2/11/time_Nm.nu
new file mode 100644
index 0000000..7298b2c
--- /dev/null
+++ b/lab_2/11/time_Nm.nu
@@ -0,0 +1,7 @@
+for x in [1024 512 256 128 64 32 16 8 4 2] {
+let filename = 'const_Nm_timings.csv';
+$x | into string | save --append $filename;
+", " | save --append $filename;
+let m = 2048000000 / $x;
+time -f %e -a -o  $filename ./memleak $x $m;
+};
\ No newline at end of file
diff --git a/lab_2/11_answer.md b/lab_2/11_answer.md
new file mode 100644
index 0000000..42d9d56
--- /dev/null
+++ b/lab_2/11_answer.md
@@ -0,0 +1,10 @@
+# What approach did you decide to follow?
+I saved the adress in present_configuration to a new pointer old_configuration so i could delete it after running the step function:
+      // Simple fix to memleak:
+      float* old_configuration = present_configuration;
+      present_configuration = crw::step(size, present_configuration);
+      delete old_configuration;
+      float present_elongation = crw::elongation(size, present_configuration);
+
+# determine the speedup
+See 11_speedup.png
diff --git a/lab_2/11_speedup.png b/lab_2/11_speedup.png
new file mode 100644
index 0000000..c2f422d
Binary files /dev/null and b/lab_2/11_speedup.png differ