timprove stability with central finite differences for displacement - slidergrid - grid of elastic sliders on a frictional surface
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       ---
 (DIR) commit 2c8a1eb434b536ba5a6bd764c8a40ff975e78a97
 (DIR) parent 29dcc40d11391606b585ee8c16d62ffab38d835d
 (HTM) Author: Anders Damsgaard <anders.damsgaard@geo.au.dk>
       Date:   Wed, 23 Mar 2016 12:13:07 -0700
       
       improve stability with central finite differences for displacement
       
       Diffstat:
         M slidergrid/slider.c                 |       6 +++---
         M test.c                              |       2 +-
       
       2 files changed, 4 insertions(+), 4 deletions(-)
       ---
 (DIR) diff --git a/slidergrid/slider.c b/slidergrid/slider.c
       t@@ -158,11 +158,11 @@ void slider_displacement(slider* s1, const slider s2,
        
            // increment in inter-slider distance, divide by two to get displacement 
            // over 1 time step
       -    //const Float3 ddist = divide_float3_scalar(
       -            //subtract_float3(dist_future, dist0), 2.0);
       +    const Float3 ddist = divide_float3_scalar(
       +            subtract_float3(dist_future, dist0), 2.0);
        
            // Get displacement change from previous and current inter-slider distance
       -    const Float3 ddist = subtract_float3(dist, dist0);
       +    //const Float3 ddist = subtract_float3(dist, dist0);
        
            //if (iteration == 0)
                //ddist = zeroes_float3();
 (DIR) diff --git a/test.c b/test.c
       t@@ -35,7 +35,7 @@ simulation setup_simulation()
                //sim.sliders[i].bond_parallel_viscosity = 1.0e2;
            }
        
       -    sim.sliders[0].vel.x = 0.1;
       +    sim.sliders[0].vel.x = 0.01;
        
            // set temporal parameters
            sim.time = 0.0;