An SDP-based Branch-and-Cut Algorithm for Biclustering

BICL-SDP is an exact algorithm, based on the branch-and-cut technique, for solving the biclustering problem through the $k$-densest-disjoint biclique criterion described in the paper "An SDP-based Branch-and-Cut Algorithm for Biclustering". This repository contains the C++ source code, the MATLAB scripts, and the datasets used for the experiments.

Installation

BICL-SDP calls the semidefinite programming solver SDPNAL+ by using the MATLAB Engine API for C++. It requires the MATLAB engine library libMatlabEngine and the Matlab Data Array library libMatlabDataArray. BICL-SDP calls the linear programming solver Gurobi and uses Armadillo to handle matrices and linear algebra operations efficiently.

Ubuntu and Debian instructions:

1. Install MATLAB (>= 2021b)

2. Install Gurobi (>= 10.0.2)

3. Install CMake, OpenBLAS, LAPACK and Armadillo:

sudo apt-get update
sudo apt-get install cmake libopenblas-dev liblapack-dev libarmadillo-dev

4. Open the makefile biclustering_cpp/Makefile

   • Set the variable matlab_path with your MATLAB folder.

5. Compile the code:

cd biclustering_cpp/
make

4. Download SDPNAL+, move the folder biclustering_matlab containing the MATLAB source code of BICL-SDP in the SDPNAL+ main directory and set the parameter SDP_SOLVER_FOLDER of the configuration file accordingly. This folder and its subfolders will be automatically added to the MATLAB search path when BICL-SDP starts.

This code has been tested under Ubuntu 22.04 LTS with MATLAB R2021b, Gurobi 10.0.2 and Armadillo 12.6.

Configuration

Various parameters used in BICL-SDP can be modified in the configuration file biclustering_cpp/config.txt:

• BRANCH_AND_BOUND_TOL - optimality tolerance of the exact algorithm
• BRANCH_AND_BOUND_PARALLEL - thread pool size: single thread (1), multi-thread (> 1)
• BRANCH_AND_BOUND_MAX_NODES - maximum number of nodes
• BRANCH_AND_BOUND_VISITING_STRATEGY - best first (0), depth first (1), breadth first (2)
• MATLAB_SESSION_THREADS_ROOT - number of threads for the MATLAB session at the root noee
• MATLAB_SESSION_THREADS_CHILD - number of threads for the MATLAB session for child nodes
• SDP_SOLVER_FOLDER - full path of SDPNAL+ folder
• SDP_SOLVER_TOL - accuracy of SDPNAL+ in the relative KKT residual
• SDP_SOLVER_VERBOSE - do not display log (0), display log (1)
• CP_MAX_ITER - maximum number of cutting-plane iterations
• CP_TOL - tolerance between two consecutive cutting-plane iterations
• CP_MAX_INEQ - maximum number of valid inequalities to separate
• CP_PERC_INEQ - fraction of the most violated inequalities to add
• CP_EPS_INEQ - tolerance for checking the violation of the inequalities
• CP_EPS_ACTIVE - tolerance for detecting active inequalities
• GUROBI_FOLDER - Gurobi solver path
• GUROBI_VERBOSE - do not display log (0), display log (1)

Usage

cd biclustering_cpp/
./bb <W_PATH> <K> <LOG_PATH> <RESULT_PATH>

• W_PATH - full path of the data matrix
• K - number of biclusters
• LOG_PATH - path of the log file
• RESULT_PATH - path of the optimal bicluster assignment matrices

File W_PATH contains the weights w_ij and the must include an header line with the number of rows n and columns m:

n m
w_11 w_12 ... w_1m
w_21 w_22 ... w_2m
...
...
w_n1 w_n2 ... w_nm

Log

The log file reports the progress of the algorithm:

• N - number of rows at the current node
• M - number of columns at the current node
• ID_PAR - id of the parent node
• ID - id of the current node
• UB_PAR - upper bound of the parent node
• UB - upper bound of the current node
• TIME (s) - running time in seconds of the current node
• CP_ITER - number of cutting-plane iterations
• CP_FLAG - termination flag of the cutting-plane procedure
  • -2 - maximum number of iterations
  • -1 - SDP not solved or partially solved successfully
  • 0 - no violated inequalities
  • 1 - node must be pruned
  • 2 - upper bound greater than the previous one
  • 3 - upper bound decrease is not sufficiently large
• CP_INEQ - number of inequalities added in the last cutting-plane iteration
• LB - current lower bound
• BEST_LB - global lower bound
• SET - vertex set selection for branching
  • U - branch on the vertices in U
  • V - branch on the vertices in V
  • -1 - branching is not needed
• I J - indices of branching decision
• NODE_GAP - gap at the current node
• GAP - overall gap
• OPEN - number of open nodes