<html><head></head><body><div class="yahoo-style-wrap" style="font-family:Helvetica Neue, Helvetica, Arial, sans-serif;font-size:13px;"><div><span>Dear Scip,<br><br>1) I encountered a discrepancy in presolve time. I used 2 methods of timing. The first is using verblevel = 5. The second is to put a timing around SCIP_CALL( SCIPpresolve(scip) ). The result is as follows. (Observe the portion in Red)<br><br>original problem has 79800 variables (0 bin, 79800 int, 0 impl, 0 cont) and 159601 constraints<br> 159600 constraints of type <linear><br> 1 constraints of type <SDP><br>Reading Time: 0.71<br><br>solve problem<br>=============<br><br>transformed problem has 79800 variables (0 bin, 79800 int, 0 impl, 0 cont) and 159601 constraints<br> 159600 constraints of type <linear><br> 1 constraints of type <SDP><br><br>original problem has 239400 active (0.00187969%) nonzeros and 239400 (0.00187969%) check nonzeros<br><br>presolving:<br>(round 1, fast) 0 del vars, 159600 del conss, 0 add conss, 159600 chg bounds, 0 chg sides, 0 chg coeffs, 0 upgd conss, 0 impls, 0 clqs<br>clique table cleanup detected 0 bound changes<br><br>presolved problem has 79800 active (100%) nonzeros and 79800 (100%) check nonzeros<br><br>presolving (2 rounds: 2 fast, 1 medium, 1 exhaustive):<br> 0 deleted vars, 159600 deleted constraints, 0 added constraints, 159600 tightened bounds, 0 added holes, 0 changed sides, 0 changed coefficients<br> 0 implications, 0 cliques<br>presolved problem has 79800 variables (79800 bin, 0 int, 0 impl, 0 cont) and 1 constraints<br> 1 constraints of type <SDP><br>transformed objective value is always integral (scale: 1)<br><font color="#9c005c">Presolving Time: 0.25</font><br><font color="#9c005c">SCIPpresolve(scip) time = 99.310370s</font><br><br>2) Also, I used >export OMP_NUM_THREADS=numCore & obtain the following. (My cpu has 6 core)<br>6 core: SCIPpresolve(scip) time = 124s<br>4 core: SCIPpresolve(scip) time = 115s<br>2 core: SCIPpresolve(scip) time = 93s<br><font color="#9c005c">1 core: SCIPpresolve(scip) time = 749s</font><br><br>3) On a larger problem, 319600 variables (0 bin, 319600 int, 0 impl, 0 cont) and 639201 constraints, the time is very long<br>SCIPpresolve(scip) time on 2 core = <font color="#9c005c">10538s</font><br><br>The scip I used is scipSdp (plugin developed by Tristan Gally). You can reproduce the behavior by compiling his plugin & I can provide the input file.<br><br></span><br></div></div></body></html>