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diff --git a/src/finite_difference_single_threaded.c b/src/finite_difference_single_threaded.c
new file mode 100644
index 0000000..5b38fd3
--- /dev/null
+++ b/src/finite_difference_single_threaded.c
@@ -0,0 +1,69 @@
+#ifndef ENABLE_MP
+
+#include "config.h"
+
+#ifdef HAVE_STDLIB_H
+#include <stdlib.h>
+#endif 
+
+#ifdef HAVE_STDIO_H
+#include <stdio.h>
+#endif 
+
+#include "definitions.h"
+
+
+extern int width, height;
+extern double **Vij, **Er;
+extern unsigned char  **oddity;
+extern int dielectrics_to_consider_just_now;
+extern double r; 
+extern int coupler;
+
+#include "exit_codes.h"
+
+double finite_difference_single_threaded()
+{
+  int i, j;
+  int number_of_iterations=25;
+  double capacitance_per_metre, energy_per_metre;
+
+  /* The following might not look very neat, with a whole load of code being 
+  written twice, when it would be posible to make it easier to read if the 
+  'if(dielectrics_in_bitmap > 1)' was in an inner loop. However, the 
+  following is almost certainly more efficient. It is not a good idea to 
+  have any more than necessary in the inner loop. 
+
+  The option to avoid the faster convergence algorithm has been didtched
+  too, as this was in an inner loop. The faster covergence method seems
+  to work fine, so there is no need to avoid using it */
+ 
+
+  /* Note, that while the number of intterations requested is set in the first
+  parameter to update_voltage_array, the actual number done is 4x higher, as 
+  each computation id done in 4 directions */
+
+  update_voltage_array(number_of_iterations, 0, width-1, 0, height-1, Vij, Vij);
+
+  /* Once the voltage distribution is found, the energy in the field may be 
+  found. This can be shown to be Energy = 0.5 * integral(E.D) dV, when 
+  integrated over a volume V, and D.E is the vector dot product of E and
+  D. 
+  
+  Energy per metre is 0.5 * D.E or (0.5*Epsilon)* E.E. Now E.E is given
+  by Ex^2 + Ey^2 (by definition of a dot product. */
+
+  energy_per_metre=0.0;
+  for(i=0;i<width;++i)
+    for(j=0;j<height;++j)
+    { 
+      energy_per_metre+=find_energy_per_metre(i,j);
+    }
+  if(coupler==FALSE)
+    capacitance_per_metre=2*energy_per_metre;
+  else
+    capacitance_per_metre=energy_per_metre;
+  return(capacitance_per_metre);
+}
+#endif /* #endif to #ifndef ENABLE_MP */
+