working gradient test (#58)

damping term now compatible with older formulation.

same formulation in wave.c for forward and gradient evaluation.

Author: joao-bapdm

simwave/kernel/backend/c_code/forward/constant_density/2d/wave.c

@@ -170,8 +170,8 @@ double forward(f_type *u, f_type *velocity, f_type *damp,
                 f_type slowness = 1.0 / (velocity[domain_offset] * velocity[domain_offset]);
 
                 // denominator with damp coefficient
-                f_type denominator = (1.0 + damp[domain_offset] * dt / (2 * slowness));
-                f_type numerator = (1.0 - damp[domain_offset] * dt / (2 * slowness));
+                f_type denominator = (1.0 + damp[domain_offset] * dt / 2 );
+                f_type numerator = (1.0 - damp[domain_offset] * dt / 2 );
 
                 value *= (dtSquared / slowness) / denominator;
 
@@ -250,7 +250,7 @@ double forward(f_type *u, f_type *velocity, f_type *damp,
                         f_type slowness = 1.0 / (velocity[domain_offset] * velocity[domain_offset]);
 
                         // denominator with damp coefficient
-                        f_type denominator = (1.0 + damp[domain_offset] * dt / (2 * slowness));
+                        f_type denominator = (1.0 + damp[domain_offset] * dt / 2 );
 
                         f_type value = dtSquared / slowness * kws * wavelet[wavelet_offset] / denominator;
 

simwave/kernel/backend/c_code/gradient/constant_density/2d/wave.c

@@ -151,8 +151,10 @@ double gradient(f_type *u, f_type *v, f_type *grad, f_type *velocity, f_type *da
                 f_type slowness = 1.0 / (velocity[domain_offset] * velocity[domain_offset]);
 
                 // denominator with damp coefficient
-                f_type denominator = (1.0 + damp[domain_offset] * dt / (2 * slowness));
-                f_type numerator = (1.0 - damp[domain_offset] * dt / (2 * slowness));
+                // f_type denominator = (1.0 + damp[domain_offset] * dt / (2 * slowness));
+                // f_type numerator = (1.0 - damp[domain_offset] * dt / (2 * slowness));
+                f_type denominator = (1.0 + damp[domain_offset] * dt / 2 );
+                f_type numerator = (1.0 - damp[domain_offset] * dt / 2 );
 
                 value *= (dtSquared / slowness) / denominator;
 
@@ -232,7 +234,8 @@ double gradient(f_type *u, f_type *v, f_type *grad, f_type *velocity, f_type *da
                         f_type slowness = 1.0 / (velocity[domain_offset] * velocity[domain_offset]);
 
                         // denominator with damp coefficient
-                        f_type denominator = (1.0 + damp[domain_offset] * dt / (2 * slowness));
+                        // f_type denominator = (1.0 + damp[domain_offset] * dt / (2 * slowness));
+                        f_type denominator = (1.0 + damp[domain_offset] * dt / 2 );
 
                         f_type value = dtSquared / slowness * kws * wavelet[wavelet_offset] / denominator;