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Fix solving objective functions of form "p = x+y+2" or similar #7

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Fix solving objective functions of form "p = x+y+2" or similar #7

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5 changes: 4 additions & 1 deletion LPdefs.js
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Original file line number Diff line number Diff line change
Expand Up @@ -73,7 +73,7 @@ var lp_noNiceSolutionErr = "No solution with the desired integer values exists"

class lpProblem
{
constructor ( problem = null ) {
constructor ( problem = null ) { // problem is itself an lpProblem
// linear expression to optimize
this.objective = (problem != null && typeof problem.objective == 'string')
? problem.objective : "";
Expand Down Expand Up @@ -122,6 +122,9 @@ class lpProblem
// similar for objective function
this.objectiveCoeffs = (problem != null && Array.isArray(problem.objectiveCoeffs))
? problem.objectiveCoeffs : [];
// e.g. the "2" in p = x+y+2
this.objectiveExtraConstant = (problem != null && typeof problem.objectiveExtraConstant == 'number')
? problem.numActualUnknowns : 0;

// additional constraints used in integer programming, indexed like integerUnknowns
this.integerMins = (problem != null && Array.isArray(problem.integerMins))
Expand Down
17 changes: 14 additions & 3 deletions LPmethods.js
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Original file line number Diff line number Diff line change
Expand Up @@ -197,7 +197,7 @@ lpProblem.prototype.solve = function ()

splitProblem( p ); // again, these may throw errors
extractUnknowns( p );
extractCoefficients( p )
extractCoefficients( p );
createFirstTableau( p );

p.status = lp_parsed; // created tableau and unknowns from problem string
Expand Down Expand Up @@ -240,7 +240,7 @@ lpProblem.prototype.solve = function ()
else
throw lp_UnspecMaxMinErr;

var coreObj = (obj.indexOf("subject") == -1)
var coreObj = (obj.indexOf("subject") == -1) // finds objective function!
? obj.substring(4)
: obj.substring(4, Math.max(5,obj.indexOf("subject")-1));
if (coreObj.indexOf("=") > -1)
Expand Down Expand Up @@ -270,7 +270,18 @@ lpProblem.prototype.solve = function ()
var outA = ("+"+p.objective)
.replace(/ /g,"")
.replace(/[\+\-][0-9.\/\(\)]*/g,",")
.replace(/,+/g,",") // removes strings of commas if there are constants in the objective function
.split(",");

if (outA[outA.length - 1] === '') { outA.pop(); }

let objConstants = [...p.objective.matchAll(/\+([0-9]+)$/g)];
objConstants = objConstants.concat([...p.objective.matchAll(/\+([0-9]+)\+/g)]);

for (let i = 0; i < objConstants.length; i++) {
p.objectiveExtraConstant = p.objectiveExtraConstant + objConstants[i][1];
}

for ( var i=0; i < p.constraints.length; i++ )
{
var kA = ("+"+p.constraints[i])
Expand Down Expand Up @@ -394,7 +405,7 @@ lpProblem.prototype.solve = function ()
}
for (var j=1;j<numRows+1;j++)
firstTableau[i].push( (i!=j)? 0 : 1 );
firstTableau[i].push(0);
firstTableau[i].push(p.objectiveExtraConstant); // objective row value?

// firstTableau.roundToSigDig(p.maxSigDigits); // round to avoid false negatives or non-zero elements
// Fix 01; in the first tableau there should be none of that, as no calculation is done prior to this
Expand Down