particle custom property getDelta in calculateForce

Sunny_21964

Dear guys

I have a question about getDelta when using calculateForce. Assuming contact of particle 1 with both particle 2 and 3, and calculateForce goes for 1-2 first, then 1-3. So when calculateForce for particle 1-particle 2, the custom property of particle 1, i.e. m_delta_1, is only the increament from interaction 1-3, or already considering the increment from interaction 1-2, as "m_delta_1 +=value" (example) is involved in multi-contacts.

PS: defining:

const double* m_value_1 = elem1CustomProperties->getValue(m_index);

double* m_delta_1 = elem1CustomProperties->getDelta(m_index);

 

Best wishes

Sunny

Richard Wood_20774

Hi,

I don't think it's that straightforward. The short version is, always use +=, but multi threading complicates things a bit. If contact(1-2) and contact(1-3) happen on different threads, they will both initially receive the same m_delta_1, increment it, and then you won't see the real value until the end of the timestep. So something like:

Time step 0:
Particle property value = 0
On thread 0 - contact (1-2) reads the property value of 0 and increments the delta +1
On thread 1 - contact (1-3) reads the property value of 0 and increments the delta +1

Time step 1:
Particle property value = 2

As you can see, the end value is correct, but neither thread ever had the correct cumulative delta. They all get summed by the solver.

Richard

satri

Hey any idea how to access the values in the debugger

because say if this is the statement as above

const double* m_value_1 = elem1CustomProperties->getValue(m_index);

when i look at the debugger and look for m_value_1[0] i keep getting this error memory cannot be read

because of which the calculation does not proceed at all

i use it to calculate

double factor = m_value_1[0]*Pi...etc

please let me know if you know of any way to resolve this