Biogeme Parameters
The parameter file provides the parameters controlling the execution of Biogeme. It is not mandatory. If it does not exist, Biogeme uses the default values, and automatically creates a file named default.par
.
If entries are missing in the file, Biogeme will use the default values.
The file is divided into sections, each section containing a list of parameters and their corresponding value.
Parameter name  Type  Default value  Description 

gevAlgo 
[GEV] 
BIO 
It selects the optimization algorithm to be used for loglikelihood estimation. Valid values: BIO , BIOMC , CFSQP , SOLVOPT , DONLP2 . Click here for more details. 
gevScreenPrintLevel 
[GEV] 
1 
This parameter defines the level of display to be produced on the screen during a run. Valid values are 1 for general messages only, 2 for detailed messages, and 3 for debug messages. 
gevLogFilePrintLevel 
[GEV] 
2 
This parameter defines the level of display to be produced in the log file during a run. Valid values are 1 for general messages only, 2 for detailed messages, and 3 for debug messages. 
gevPrintVarCovarAsList 
[GEV] 
1 
If set to 1, the variancecovariance matrix of the estimated parameters is displayed as a list (one row per entry). 
gevPrintVarCovarAsMatrix 
[GEV] 
0 
If set to 1, the variancecovariance matrix of the estimated parameters is displayed as a matrix. We recommend to use this feature only if the number of parameters is small (not more than 10). 
gevAutomaticScalingOfLinearUtility 
[GEV] 
0 
If 1, linear utility functions are automatically scaled to avoid numerical problems during the estimation. The scaling is computed in such a way that all attributes have a level of magnitude of about 1.0. 
gevBinaryDataFile 
[GEV] 
__BiogemeData.bin 
This is the name of the binary data file where the processed data are stored. 
gevBufferSize 
[GEV] 
100000 
Biogeme reads the first line of the data files, and stores it in a buffer to analyze it and extract the labels. The size of the buffer is determined by this parameter. Adjust the value if the first line of your data file contains more that 99'999 characters. Biogeme provides a warning if the default value is exceeded. 
gevCheckDerivatives 
[GEV] 
0 
If set to 1, the analytical derivatives of the loglikelihood functions and the nonlinear constraints are compared to the finite difference derivatives. This is used basically when a new model is included and for debugging purposes. 
gevDataFileDisplayStep 
[GEV] 
500 
While preprocessing the data file before the estimation, Biogeme reports progress each time it has read a number of rows specified by this parameter. 
gevDebugDataFirstRow 
[GEV] 
0 
Biogeme can print what it actually reads from the data file. This parameter is the number of the first row for which his information is displayed. It is recommended to use it when strange results are generated by the package. It helps identifying garbage in the data file, such as strings, for instance. 
gevDebugDataLastRow 
[GEV] 
0 
Biogeme can print what it actually reads from the data file. This parameter is the number of the last row for which his information is displayed. It is recommended to use it when strange results are generated by the package. It helps identifying garbage in the data file, such as strings, for instance. 
gevDecimalDigitsStats 
[GEV] 
3 
Number of digits after the decimal points to be used for printing general statistics in the output files. 
gevDecimalDigitsTTest 
[GEV] 
2 
Number of digits after the decimal points to be used for printing ttests in the output files. 
gevDumpDrawsOnFile 
[GEV] 
0 
If set to 1, Biogeme dumps the draws used for simulated likelihood estimation. The name of the file is displayed at the end of the run. If the model name is model , the filename is model.draws . 
gevForceScientificNotation 
[GEV] 
0 
If 1, use the scientific notation for printing results. 
gevGenerateActualSample 
[GEV] 
0 
If set to 1, Biogeme generates a copy of the sample file containing only the observations that have not been excluded. 
gevMinimumMu 
[GEV] 
1.0e5 
When the homogeneity parameter μ of MEV models is estimated, its theoretical lower bound must be zero. However, numerically, a value of 0 generates problems during the computation of the model. Therefore, the lower bound is automatically set to the value defined by this parameter. 
gevMaxPrimeNumber 
[GEV] 
1000 
The generation of Halton sequences is based on prime numbers. This parameter defines the maximum number of prime numbers that can be used. Most users will never have to change the default value. But if it is too low, an error message is generated: Warning: Error: 23 Halton series must be generated, but there are only 10 prime numbers available. Increase the value of gevMaxPrimeNumber in the parameters file 
gevMissingValue 
[GEV] 
99999 
This parameter is used mainly for debugging purposes. It defines the value given to missing values in the data file. If one of them is used in the computation of the utility functions, an error message is triggered. 
gevNonParamPlotRes 
[GEV] 
100 
This parameter defines the number of equally distributed values on the xaxis used to generate nonparametric plots (Biosim only) . 
gevNonParamPlotMaxY 
[GEV] 
1000 
When generating nonparametric plots, values larger that this parameter are considered equal to the parameter. Symmetrically, values lower than the negative parameter are considered equal to the negative value. 
gevNonParamPlotXSizeCm 
[GEV] 
15 
Width in centimeters of the nonparametric plots in the \LaTeX\ output. 
gevNonParamPlotMinXSizeCm 
[GEV] 
0.00001 
Units on the xaxis are computed automatically for nonparametric plots, but will no be lower than the value of this parameter. 
gevNonParamPlotMinYSizeCm 
[GEV] 
0.00001 
Units on the yaxis are computed automatically for nonparametric plots, but will no be lower than the value of this parameter./td> 
gevOne 
[GEV] 
one 
Name of the expression that is replaced by the value 1.0. It can be used in the specification of the utility without explicitly defining it in the Section [Expressions] . 
gevOutputActualSample 
[GEV] 
__actualSample.dat 
If the parameter gevGenerateActualSample is set to 1, this parameter defines the name of the file where the sample is saved. 
gevPrintPValue 
[GEV] 
1 
If 1, print the pvalue in the results. The pvalue is computed as follows: if t is the ttest of the parameters, then p = 2 (1  Φ(t)), where Φ(.) is the cumulative density function of the univariate normal distribution. 
gevRandomDistrib 
[GEV] 
PSEUDO 
Type fo draws use for simulating random distributions. Valid values are

gevSaveIntermediateResults 
[GEV] 
0 
If 1, the current estimates are saved at each iteration in a file with extension .bck . This is particularly useful for models that take a while to estimate, so that the estimation can be restarted from the last iterate. 
gevSeed 
[GEV] 
9021967 
It defines the seed value for the pseudorandom number generator. 
gevSignificantDigitsParameters 
[GEV] 
3 
Number of significant digits to be used for printing estimated parameters in the output files. 
gevSingularValueThreshold 
[GEV] 
1.0e4 
Identification problems are analyzed using a Singular Value Decomposition procedure. If a singular value is small (that is, its absolute value is less than the value defined by this parameter), the model is considered degenerate and the source of this degeneracy is displayed. 
gevStopFileName 
[GEV] 
STOP 
During the optimization process, Biogeme checks for the existence of a file, whose name is defined by this parameter. If the file exists, Biogeme interrupts the iterations and generate output files. This is convenient to prematurely stop iterations without loosing the computations performed thus far. 
gevStoreDataOnFile 
[GEV] 
0 
Biogeme uses a database gathering the processed data from the file provided by the user and, if applicable, the draws for the simulated maximum likelihood estimation. If the parameter is 0, the database is stored in memory. If 1, it is stored in the binary file defined by the parameter gevBinaryDataFile . It is recommended to use 0, except if the data does not fit in memory. Indeed, accessing to the file slows down the estimation process. 
gevSummaryFile 
[GEV] 
summary.html 
Name of the file summarizing the results of several runs of Biogeme. 
gevSummaryParameters 
[GEV] 
summary.lis 
Name of the file containing the name of the parameters whose estimated values must be reported in the summary file. 
gevVarCovarFromBHHH 
[GEV] 
0 
The computation of the variancecovariance matrix of the estimated parameters using finite difference approximation may take a while for complex models. It is sometimes useful to use the BHHH approximation, which is much faster to compute. If so, set this parameter to 1. It is recommended not to use BHHH in the final model. 
gevTtestThreshold 
[GEV] 
1.96 
Set the threshold for the ttest hypothesis tests. If the absolute value of a ttest is less than gevTtestThreshold , a symbol * will be appended to the relevant line in the report file. 
gevWarningLowDraws 
[GEV] 
1000 
Biogeme displays a warning if the number of draws for simulated maximum likelihood estimation is considered too low. This parameter defines the threshold used in the generation of this warning message. Note that it has no effect on the estimation itself. 
gevWarningSign 
[GEV] 
* 
When a ttest is not successful, a warning size is displayed in the report file and in the HTML file. This parameter defines the nature of this sign. 
BTRMaxIter 
[BasicTrustRegion] 
1000 
Maximum number of iterations to be performed. 
BTRTypf 
[BasicTrustRegion] 
1.0 
Typical value of the log likelihood function, with opposite sign 
BTRTolerance 
[BasicTrustRegion] 
6.05545e06 
Value used for the stopping criterion. 
BTRCheapHessian 
[BasicTrustRegion] 
1 
If 1, BHHH (see Berndt et al, 1974) is used as an approximation of the second derivatives matrix. 
BTRUsePreconditioner 
[BasicTrustRegion] 
0 
If 1, the subproblem is preconditioned using a modified Cholesky factorization (see Schnabel and Eskow, 1991). 
BTRInitRadius 
[BasicTrustRegion] 
1.0 
Defines the initial radius of the trust region. 
BTRIncreaseTRRadius 
[BasicTrustRegion] 
2.0 
Defines the factor by which the radius of the trust region is multiplied after a successful iteration. 
BTRMinTRRadius 
[BasicTrustRegion] 
1.0e7 
Defines the minimum radius of the trust region. If this radius is reached, the iterations are interrupted. 
BTRMaxTRRadius 
[BasicTrustRegion] 
1.0e10 
Defines the maximum radius of the trust region. If this radius is reached, the trust region is not enlarged anymore. 
BTRStartDraws 
[BasicTrustRegion] 
10 
If BIOMC is used for simulated maximum likelihood estimation, this parameter defines the number of draws which are used during the first iterations. 
BTRIncreaseDraws 
[BasicTrustRegion] 
2 
If BIOMC is used for simulated maximum likelihood estimation, this parameters defines the factor by which the number of draws is increased. 
cfsqpIprint 
[cfsqp] 
1 
Set it to 1 for silent mode, and to 2 for information at each iteration of the optimization algorithm. 
cfsqpMaxIter 
[cfsqp] 
500 
Maximum number of iterations. 
cfsqpMode 
[cfsqp] 
110 
Even if it is a descent algorithm, CFSQP sometimes allows nonmonotone iterates, hoping not to be trapped in local minima. If the function is convex, a descent algorithm is more appropriate. In this case, set the value to 100. See CFSQP manual for more details. 
cfsqpEps 
[cfsqp] 
6.05545e06 
See CFSQP manual. In general, it should not be changed. 
cfsqpEpsEqn 
[cfsqp] 
6.05545e06 
See CFSQP manual. In general, it should not be changed. 
cfsqpUdelta 
[cfsqp] 
0.0 
See CFSQP manual. In general, it should not be changed. 
solvoptMaxIter 
[solvopt] 
15000 
Maximum number of iterations. 
solvoptDisplay 
[solvopt] 
1 
Controls the display of the algorithm. See SOLVOPT manual. 
solvoptErrorArgument 
[solvopt] 
1.0e4 
See SOLVOPT manual. In general, it should not be changed. 
solvoptErrorFunction 
[solvopt] 
1.0e6 
See SOLVOPT manual. In general, it should not be changed. 
donlp2Epsx 
[donlp2] 
1.0e5 
See DONLP2 manual. In general, it should not be changed. 
donlp2Delmin 
[donlp2] 
1.0e6 
See DONLP2 manual. In general, it should not be changed. 
donlp2Smallw 
[donlp2] 
3.66685e11 
See DONLP2 manual. In general, it should not be changed. 
donlp2Epsdif 
[donlp2] 
0.0 
See DONLP2 manual. In general, it should not be changed. 
donlp2NReset 
[donlp2] 
9 
See DONLP2 manual. In general, it should not be changed. 