1. mps-tk : A C++ toolkit for multiple-point simulation
Alexandre Boucher
Advanced Resources and Risk Technology, LLC
Stanford University, ERE
Toan Tran
Stanford University, EE

2. Objectives of the toolkit
A SGeMS-based C++ library to ease development of mps algorithms
Present abstraction of mps components
Provide a set of coherent mps building blocks to developers
Provide implementation examples
Stepping stone for the next generation of mps algorithms
Target user is a developer not a geomodeler
NOTE: goal is to develop tools to build mps algorithms not write new algorithms.

3. Generic mps simulation algorithm
Imposition of a spatial texture (geology) on a grid such that it conforms to data.
Patterns
Database
The patterns database is typically built from training images
A sequential simulation algorithm builds and queries that database
The simulation is not based on the training image per se, but from the patterns extracted from that training image

4. Generic sequential simulation algorithm
Pattern
Database

5. Generic sequential simulation algorithm
Pattern
Database

6. Texture is function of the patterns database
The pattern database controls the look of the simulated geology
The data control the locations of some texture element

7. Generic abstraction of mps
Patterns database
Known values and ancillary data (trends, regions, angles, …)
Data event extracted from the grid and ancillary data
Sampler
Select a replicate from the list returned from the pattern database
Replicates returned from the database that match the data event. May take different forms (e.g. distributions)
Probability field adjustment

8. Abstraction components
Data event Pattern and information retrieved from the simulation grid
Pattern database Find patterns matching the data-event
Replicates Outputs from the database
Sampler Select a replicate from the collection of replicates

9. Libraries included in mps-tk
mps_dataevent Contains all the dev related functionalities
mps_pattern_database Database and functionalities to build new database
mps_replicate Sampler, servo-system and collection of replicates
mps_app_utility Base classes and utilities that link mps-tk together
mps_parallelism Task manager for multi-threading
Unit testing Functionality and regression testing

10. mps_dataevent Created with either?
Geovalue_dataevent
Data-event around a central location (+ ancillary data)
Fixed_template_geodev_builder
Global_template_geodev_builder
Directional_overlap_dataevent
Directional_overlap_dev_builder ?
Created with
Dataevent_distance
Compute the similarity between two data events
Distance ,

11. mps_pattern_database
Search_tree_pattern_database
Build a search tree
Scanning_pattern_database
Search the TI for any data configuration.
Searched with
Fixed_template_pattern_database
Decompose the TI into patterns with fixed shape
Cross_correlation_pattern_database
Fourier space
TI values ready for convolution
Multigrid_pattern_database
patDB-1 ,
, … ,
One database per multi-grid

12. mps_replicate Results from the pattern database ,
Collection_replicate
Results from the pattern database
Cdf_replicate
Conditional distribution from the pattern database
Monte Carlo drawing from replicates
Pixel-based simulation
Draw from a distribution given the constraint of a servo system
Cdf_servo_sampler
Draw from a distribution given the constraint of a servo system with a probability field
Updating_cdf_servo_sampler
Patch-based simulation
Random_replicate_sampler
Draw a replicate from a collection of replicates

13. Mps_parallelism
Computational_task
Encapsulates data and a processing method to be executed by a computational resource (thread or process).
Computational_task_manager
Uses threads to execute tasks
Currently uses the Boost thread library for shared memory machine. Designed to be extended to distributed memory applications.
Platform-independent (Windows, Linux)
To run in parallel, write cpu-intensive process as a Computational_task

14. Type of parallelisms implemented
Parallel task manager applied within a data base (e.g. patterns scanning )
patDB
Task 1
Task 2 …
Task N
Parallel task manager applied to a full simulation (e.g. CCSIM)
patDB-1
Task 1 …
patDB-1
Task N

15. A note on hard data conditioning
Lack of standard approach for conditioning in mps
Copy data on grid
Built-in conditioning (snesim)
Distance-weighted function (filtersim)
Adaptive data event (ccsim)
Rejection approach
Objectives:
mps-tk does not interfere with conditioning approaches.
mps-tk offers flexibility to implement the appropriate conditioning technique.

16. Build a scanning pattern database
// set basic data event builder
dataevent_builder->grid_is(training_image_);
dataevent_builder->neighborhood_is(subgrid_ti_neighborhoods_);
// set trend data event builder
trend_dev_builder->dataevent_builder_is(dataevent_builder);
trend_dev_builder->trend_property_is(training_image_trend_property_);
fixed_template_pattern_db_->dataevent_builder_is(trend_dev_builder);
// set dev_distance to pattern database
fixed_template_pattern_db_->dataevent_distance_is(trend_dataevent_distance_);
// Create and set dev_selector to pattern database
dataevent_selector->k_number_is(k_number);
// set dev_selector to pattern database
fixed_template_pattern_db_->dataevent_selector_is(dataevent_selector_);

17. Pattern database with multiple grid
Multigrid_pattern_database
A collection of database; one for each multiple grid
Each multi-grid can use a different pattern database
multigrid_scanning_pattern_db_ = Multigrid_pattern_database< Geovalue_dataevent, Collection_replicate<Geovalue_dataevent> >::Ptr_new();
for (int mgrid = 0; mgrid <= nb_mgrids_; mgrid++) {
scanning_pattern_db_ = Scanning_pattern_database::Ptr_new();
// … initialize individual pattern database …
// add database to the mgrid database
multigrid_scanning_pattern_db_->pattern_database_add(scanning_pattern_db_); }

18. Multi-grid simulation with a scanning database
/* Loop for all multiple grids */
for (int mgrid = nb_mgrids_; mgrid >= 0; mgrid--){
/* initialize simulation path */
RGrid::random_path_iterator path_begin = simul_grid_->random_path_begin();
RGrid::random_path_iterator path_end = simul_grid_->random_path_end();
/* Set subgrid to multigrid_pattern_databases */
multigrid_fixed_template_pattern_db_->current_subgrid_is(subgrid);
/* Run simulation */
pixel_based_simulate( path_begin, path_end, fixed_template_dev_builder_.get(), multigrid_fixed_template_pattern_db_.get(),sampler_.get() ); }

19. CCSIM algorithm
The data event builder and the FFT-based database were previously initialized
for (; _path_begin != _path_end; _path_begin++) {
/* Create the data event */
Directional_overlap_dataevent::Ptr
simul_dev = simul_dev_builder_->dataevent(*_path_begin);
/* Get the collection of replicates from the pattern database*/
Lazy_collection_replicate<Directional_overlap_dataevent>::Ptr
replicates = ccsim_pattern_db_->replicate(simul_dev);
/* Randomly draw a replicate from the selected set of replicates*/
sampler_->sample(replicates); }

20. Development and perspectives
Immediate goal is to provide tools to develop new algorithms
Write more examples to expand and test the components and the design libraries
GPU-powered pattern database
Parallelism on server with MPI
Complex gridding
Offer new perspectives
Meta-pattern database : a database of several databases
Pattern database not derived from a TI: e.g. process-based equations
Cloud-based pattern database