Bison 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.

To sort the table, click on the header "Parameter name" or "Section".

Parameter name Section Default value Description
gevAlgo [GEV] BIO It selects the optimization algorithm to be used for log-likelihood estimation. Valid values: BIO, BIOMC, CFSQP, SOLVOPT, DONLP2. Click here for more details. Top
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. Top
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. Top
gevPrintVarCovarAsList [GEV] 1 If set to 1, the variance-covariance matrix of the estimated parameters is displayed as a list (one row per entry). Top
gevPrintVarCovarAsMatrix [GEV] 0 If set to 1, the variance-covariance 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). Top
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. Top
gevBinaryDataFile [GEV] __BiogemeData.bin This is the name of the binary data file where the processed data are stored. Top
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. Top
gevCheckDerivatives [GEV] 0 If set to 1, the analytical derivatives of the log-likelihood 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. Top
gevDataFileDisplayStep [GEV] 500 While pre-processing the data file before the estimation, Biogeme reports progress each time it has read a number of rows specified by this parameter. Top
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. Top
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. Top
gevDecimalDigitsStats code>[GEV] 3 Number of digits after the decimal points to be used for printing general statistics in the output files. Top
gevDecimalDigitsTTest [GEV] 2 Number of digits after the decimal points to be used for printing t-tests in the output files. Top
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. Top
gevForceScientificNotation [GEV] 0 If 1, use the scientific notation for printing results. Top
gevGenerateActualSample [GEV] 0 If set to 1, Biogeme generates a copy of the sample file containing only the observations that have not been excluded. Top
gevMinimumMu [GEV] 1.0e-5 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. Top
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 Top
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. Top
gevNonParamPlotRes [GEV] 100 This parameter defines the number of equally distributed values on the x-axis used to generate nonparametric plots (Biosim only) . Top
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. Top
gevNonParamPlotXSizeCm [GEV] 15 Width in centimeters of the nonparametric plots in the \LaTeX\ output. Top
gevNonParamPlotMinXSizeCm [GEV] 0.00001 Units on the x-axis are computed automatically for nonparametric plots, but will no be lower than the value of this parameter. Top
gevNonParamPlotMinYSizeCm [GEV] 0.00001 Units on the y-axis are computed automatically for nonparametric plots, but will no be lower than the value of this parameter./td> Top
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]. Top
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. Top
gevPrintPValue [GEV] 1 If 1, print the p-value in the results. The p-value is computed as follows: if t is the t-test of the parameters, then p = 2 (1 - Φ(t)), where Φ(.) is the cumulative density function of the univariate normal distribution. Top
gevRandomDistrib [GEV] PSEUDO Type fo draws use for simulating random distributions. Valid values are
  • PSEUDO: Pseudo random numbers
  • HALTON: Halton sequences
  • MLHS: Modified Latin Hypercube Sampling (see Hess et al., 2006).
Top
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. Top
gevSeed [GEV] 9021967 It defines the seed value for the pseudo-random number generator. Top
gevSignificantDigitsParameters [GEV] 3 Number of significant digits to be used for printing estimated parameters in the output files. Top
gevSingularValueThreshold [GEV] 1.0e-4 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. Top
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. Top
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. Top
gevSummaryFile [GEV] summary.html Name of the file summarizing the results of several runs of Biogeme. Top
gevSummaryParameters [GEV] summary.lis Name of the file containing the name of the parameters whose estimated values must be reported in the summary file. Top
gevVarCovarFromBHHH [GEV] 0 The computation of the variance-covariance 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. Top
gevTtestThreshold [GEV] 1.96 Set the threshold for the t-test hypothesis tests. If the absolute value of a t-test is less than gevTtestThreshold, a symbol * will be appended to the relevant line in the report file. Top
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. Top
gevWarningSign [GEV] * When a t-test 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. Top
BTRMaxIter [BasicTrustRegion] 1000 Maximum number of iterations to be performed. Top
BTRTypf [BasicTrustRegion] 1.0 Typical value of the log likelihood function, with opposite sign Top
BTRTolerance [BasicTrustRegion] 6.05545e-06 Value used for the stopping criterion. Top
BTRCheapHessian [BasicTrustRegion] 1 If 1, BHHH (see Berndt et al, 1974) is used as an approximation of the second derivatives matrix. Top
BTRUsePreconditioner [BasicTrustRegion] 0 If 1, the subproblem is preconditioned using a modified Cholesky factorization (see Schnabel and Eskow, 1991). Top
BTRInitRadius [BasicTrustRegion] 1.0 Defines the initial radius of the trust region. Top
BTRIncreaseTRRadius [BasicTrustRegion] 2.0 Defines the factor by which the radius of the trust region is multiplied after a successful iteration. Top
BTRMinTRRadius [BasicTrustRegion] 1.0e-7 Defines the minimum radius of the trust region. If this radius is reached, the iterations are interrupted. Top
BTRMaxTRRadius [BasicTrustRegion] 1.0e10 Defines the maximum radius of the trust region. If this radius is reached, the trust region is not enlarged anymore. Top
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. Top
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. Top
cfsqpIprint [cfsqp] 1 Set it to 1 for silent mode, and to 2 for information at each iteration of the optimization algorithm. Top
cfsqpMaxIter [cfsqp] 500 Maximum number of iterations. Top
cfsqpMode [cfsqp] 110 Even if it is a descent algorithm, CFSQP sometimes allows non-monotone 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. Top
cfsqpEps [cfsqp] 6.05545e-06 See CFSQP manual. In general, it should not be changed. Top
cfsqpEpsEqn [cfsqp] 6.05545e-06 See CFSQP manual. In general, it should not be changed. Top
cfsqpUdelta [cfsqp] 0.0 See CFSQP manual. In general, it should not be changed. Top
solvoptMaxIter [solvopt] 15000 Maximum number of iterations. Top
solvoptDisplay [solvopt] 1 Controls the display of the algorithm. See SOLVOPT manual. Top
solvoptErrorArgument [solvopt] 1.0e-4 See SOLVOPT manual. In general, it should not be changed. Top
solvoptErrorFunction [solvopt] 1.0e-6 See SOLVOPT manual. In general, it should not be changed. Top
donlp2Epsx [donlp2] 1.0e-5 See DONLP2 manual. In general, it should not be changed. Top
donlp2Delmin [donlp2] 1.0e-6 See DONLP2 manual. In general, it should not be changed. Top
donlp2Smallw [donlp2] 3.66685e-11 See DONLP2 manual. In general, it should not be changed. Top
donlp2Epsdif [donlp2] 0.0 See DONLP2 manual. In general, it should not be changed. Top
donlp2NReset [donlp2] 9 See DONLP2 manual. In general, it should not be changed. Top