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	tfurther benchmarking of contact model 1 - sphere - GPU-based 3D discrete eleme…
	git clone git://src.adamsgaard.dk/sphere
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	---
	commit fa1b2b156a00f420270c8fec8b39e96e48e0fb00
	parent 3436b77c5e376849b25d099efd1f21570c1b5aa0
	Author: Anders Damsgaard <[email protected]>
	Date: Thu, 22 Nov 2012 10:39:20 +0100

	further benchmarking of contact model 1

	Diffstat:
	M src/contactmodels.cuh \| 52 ++++++++++++++++++++++++++---…
	M src/device.cu \| 2 +-

	2 files changed, 46 insertions(+), 8 deletions(-)
	---
	diff --git a/src/contactmodels.cuh b/src/contactmodels.cuh
	t@@ -254,6 +254,32 @@ __device__ void contactLinearViscous(Float3* F, Float3* T,


	// Linear elastic contact model for particle-particle interactions
	+/__device__ void contactLinear_bck(Float3 F, Float3* T,
	+ Float* es_dot, Float* ev_dot, Float* p,
	+ unsigned int idx_a_orig,
	+ unsigned int idx_b_orig,
	+ Float4 vel_a,
	+ Float4* dev_vel,
	+ Float3 angvel_a,
	+ Float4* dev_angvel,
	+ Float radius_a, Float radius_b,
	+ Float3 x_ab, Float x_ab_length,
	+ Float delta_ab, Float4* dev_delta_t,
	+ unsigned int mempos)
	+{
	+ Float4 vel_b = dev_vel[idx_b_orig];
	+ Float4 angvel4_b = dev_vel[idx_b_orig];
	+
	+ // Fe
	+
	+
	+
	+
	+}*/
	+
	+
	+
	+// Linear elastic contact model for particle-particle interactions
	__device__ void contactLinear(Float3* F, Float3* T,
	Float* es_dot, Float* ev_dot, Float* p,
	unsigned int idx_a_orig,
	t@@ -364,12 +390,18 @@ __device__ void contactLinear(Float3* F, Float3* T,
	f_t = MAKE_FLOAT3(0.0f, 0.0f, 0.0f);
	//T_res = MAKE_FLOAT3(0.0f, 0.0f, 0.0f);

	+ //cuPrintf("mu_s = %f\n", devC_params.mu_s);
	+
	// Apply a tangential force if the previous tangential displacement
	// is non-zero, or the current sliding velocity is non-zero.
	if (delta_t0_length > 0.0 \|\| vel_t_ab_length > 0.0) {

	+ // Add tangential displacement to total tangential displacement
	+ delta_t = delta_t0 + vel_t_ab * devC_dt;
	+
	// Tangential force: Visco-Elastic, before limitation criterion
	- Float3 f_t_elast = -devC_params.k_t * delta_t0;
	+ //Float3 f_t_elast = -devC_params.k_t * delta_t0;
	+ Float3 f_t_elast = -devC_params.k_t * delta_t;
	Float3 f_t_visc = -devC_params.gamma_t * vel_t_ab;
	f_t = f_t_elast + f_t_visc;
	Float f_t_length = length(f_t);
	t@@ -377,14 +409,17 @@ __device__ void contactLinear(Float3* F, Float3* T,
	// Static frictional limit
	Float f_t_limit = devC_params.mu_s * length(f_n-f_c);

	+
	// If failure criterion is not met, contact is viscous-linear elastic.
	// If failure criterion is met, contact force is limited,
	// resulting in a slip and energy dissipation
	if (f_t_length > f_t_limit) { // Static friciton exceeded: Dynamic case
	+
	+ //cuPrintf("slip! %f > %f\n", f_t_length, f_t_limit);

	// Frictional force is reduced to equal the dynamic limit
	- //f_t = (devC_params.mu_d length(f_n-f_c))/f_t_length;
	- f_t = -devC_params.mu_d * length(f_n - f_c) * delta_t0/length(delta_t0);
	+ f_t = (devC_params.mu_d length(f_n-f_c))/f_t_length;
	+ //f_t = f_t * (devC_params.mu_d * f_n_length)/f_t;

	// A slip event zeros the displacement vector
	//delta_t = MAKE_FLOAT3(0.0f, 0.0f, 0.0f);
	t@@ -395,6 +430,8 @@ __device__ void contactLinear(Float3* F, Float3* T,
	//delta_t = -1.0f/devC_params.k_t * (f_t + devC_params.gamma_t * vel_t_a…
	//delta_t = -1.0f/devC_params.k_t * f_t;
	delta_t = -1.0/devC_params.k_t * f_t + devC_params.gamma_t * vel_t_ab;
	+ //delta_t = devC_params.k_t * f_t_limit * vel_t_ab/vel_t_ab_length
	+ //+ devC_params.gamma_t * vel_t_ab;

	// Shear friction heat production rate:
	// The energy lost from the tangential spring is dissipated as heat
	t@@ -403,15 +440,17 @@ __device__ void contactLinear(Float3* F, Float3* T,
	es_dot += length(length(f_t) vel_t_ab * devC_dt) / devC_dt; // Seen i…
	//*es_dot += fabs(dot(delta_t0 - delta_t, f_t)) / devC_dt;

	- } else { // Static case
	+ } //else { // Static case
	+ //cuPrintf("no slip: %f < %f\n", f_t_length, f_t_limit);

	// No correction of f_t is required

	// Add tangential displacement to total tangential displacement
	- delta_t = delta_t0 + vel_t_ab * devC_dt;
	- }
	+ //delta_t = delta_t0 + vel_t_ab * devC_dt;
	+ //}
	}

	+
	//if (angvel_ab_length > 0.f) {
	// Apply rolling resistance (Zhou et al. 1999)
	//T_res = -angvel_ab/angvel_ab_length * devC_params.mu_r * R_bar * length(…
	t@@ -426,7 +465,6 @@ __device__ void contactLinear(Float3* F, Float3* T,
	//}

	// Add force components from this collision to total force for particle
	- //*F += f_n + f_t + f_c;
	*F += f_n + f_t + f_c;
	// Add torque components from this collision to total torque for particle
	// Comment out the line below to disable rotation
	diff --git a/src/device.cu b/src/device.cu
	t@@ -16,7 +16,7 @@
	#include "constants.cuh"
	#include "debug.h"

	-//#include "cuPrintf.cu"
	+#include "cuPrintf.cu"

	#include "sorting.cuh"
	#include "contactmodels.cuh"