Ensure that init_flow is used in conjunction with init

README.md

@@ -161,6 +161,11 @@ should be a `;` sperated list of `key=value` pairs. The possible keys are
   be `RK4` for Runge-Kutta 4 (default) or `RK2` for Runge-Kutta 2. Adaptive
   step algorithms cannot be used for the tangent flow.
 
+* `init_flow` (`identity` or `file` (default)): if set to `file`, then read the
+  initial condition for the tangent flow (used for the Lyapunov exponent
+  computation) from the init file (the same as for `init`, which needs to be
+  specified). Otherwise, the flow is initialized as the identity matrix.
+
 
 # Interrupting and resuming the computation
 

src/main.c

@@ -686,6 +686,12 @@ int read_params(
     parameters->lyapunov_reset=parameters->print_freq;
   }
 
+  // check that if flow_init is used, then so is init
+  if(parameters->init_flow_file && parameters->init!=INIT_FILE){
+    fprintf(stderr, "error: cannot use 'init_flow:file' if 'init' is not a binary file\n");
+    return(-1);
+  }
+
   return(0);
 }