📄 gslib help sasim.htm
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<H2>GSLIB Help Page: SASIM</H2></CENTER>
<DL>
<DT><IMG height=14 alt=o src="GSLIB Help SASIM.files/ball.red.gif" width=14>
<STRONG>Description:</STRONG>
<UL>
<LI><TT>sasim</TT> allows conditional simulations of a continuous variable
honoring any combination of the following input statistics: histogram,
variogram, indicator variograms, correlation coefficient with a secondary
variable, or conditional distributions with a secondary variable. </LI></UL>
<DT><IMG height=14 alt=o src="GSLIB Help SASIM.files/ball.red.gif" width=14>
<STRONG>Parameters:</STRONG>
<UL>
<LI><B>objhist, objvarg, objivar, objcorr, objcpdf:</B> binary flags that
specify whether or not a component objective function will be considered
(set to 1 if yes, 0 if not).
<LI><B>sclhist, sclvarg, sclivar, sclcorr, sclcpdf:</B> user imposed scaling
factors that will multiply the scaling factors that the program
automatically calculates (see section V.6).
<LI><B>ilog:</B> if set to 1, the logarithm (base 10) of the variable will
be considered. This is appropriate for positively skewed variables with
large variance.
<LI><B>nsim:</B> the number of realizations to generate.
<LI><B>nx, xmn, xsiz:</B> definition of the grid system (<I>x</I> axis).
<LI><B>ny, ymn, ysiz:</B> definition of the grid system (<I>y</I> axis).
<LI><B>nz, zmn, zsiz:</B> definition of the grid system (<I>z</I> axis).
<LI><B>seed:</B> random number seed (a large odd integer).
<LI><B>idbg:</B> an integer debugging level between 0 and 3.
<LI><B>dbgfl:</B> the file for the debugging output.
<LI><B>outfl:</B> the output grid is written to this file. The output file
will contain the results, cycling fastest on <I>x</I> then <I>y</I> then
<I>z</I> then simulation by simulation.
<LI><B>isas:</B> the annealing schedule (next set of parameters) can be set
explicitly or it can be set automatically (0=automatic,1=then use the next
three lines of input).
<LI><B>t0, redfac, ka, k, num, omin:</B> the annealing schedule: initial
temperature, the reduction factor, the maximum number of perturbations at
any one given temperature, and the target number of acceptable perturbations
at a given temperature, the stopping number (maximum number of times that
the <B>ka</B> is reached), and a low objective function value indicating
convergence.
<LI><B>maxpert:</B> the maximum number of perturbations (will be scaled by
<B>nx</B> x <B>ny</B> x <B>nz</B>)
<LI><B>report:</B> After a fixed number of swaps (<B>report</B> scaled by
<B>nx</B> x <B>ny</B> x <B>nz</B>) the objective function is written to the
screen and the debugging file.
<LI><B>icond:</B> set to 1 if there is conditioning data (0 implies no
conditioning data).
<LI><B>condfl:</B> an input data file with the conditioning data (simplified
Geo-EAS format). If this file does not exist then an unconditional
simulation is generated.
<LI><B>icolx, icoly, icolz,</B> and <B>icolvr:</B> the column numbers for
the <I>x,y,</I> and <I>z</I> coordinates and the variable to be simulated.
One or two of the coordinate column numbers can be set to zero which
indicates that the simulation is 2-D or 1-D.
<LI><B>tmin</B> and <B>tmax:</B> all values strictly less than <B>tmin</B>
and strictly greater than <B>tmax</B> are ignored.
<LI><B>ihist:</B> set to 1 if the histogram should be taken from the
following file (set to 0 if not).
<LI><B>histfl:</B> an input data file with the histogram in simplified
Geo-EAS format.
<LI><B>icolvr,</B> and <B>icolwt:</B> the column numbers for the variable to
be simulated and a declustering weight.
<LI><B>nquant:</B> number of quantiles for the histogram objective function
<LI><B>nivar:</B> number of indicator variograms to consider. The threshold
values (in units of the primary variable) are input next and the variograms
are input directly after the direct variogram of the primary variable with
the same format.
<LI><B>ithreshold:</B> The threshold values (in units of the primary
variable) for the indicator variograms
<LI><B>secfl:</B> an input data file with the secondary variable model
(needed if cosimulation is being performed)
<LI><B>icolsec:</B> the column number for the secondary variable in
<B>secfl</B>
<LI><B>vertavg:</B> if set to 1, then the correlation applies to the
secondary variable and a vertical average of the variable being simulated.
Otherwise, the secondary variable is considered at each grid node location.
<LI><B>corrcoef:</B> The correlation coefficient (used if the fourth
component objective function is turned on).
<LI><B>bivfl:</B> an input data file with the bivariate data to define the
conditional distributions (simplified Geo-EAS format)
<LI><B>icolpri</B> and <B>icolsec:</B> the column numbers for the primary
and secondary variables in <B>bivfl</B>
<LI><B>tmin</B> and <B>tmax:</B> all values strictly less than <B>tmin</B>
and strictly greater than <B>tmax</B> are ignored.
<LI><B>npricut:</B> number of thresholds to define the conditional
distributions of the primary variable within a class of the secondary
variable.
<LI><B>nseccut:</B> number of thresholds to define the classes of secondary
variable.
<LI><B>nlag:</B> the number of variogram lags to consider in the objective
function. The closest <B>nlag</B> lags, measured in terms of variogram
distance, are retained.
<LI><B>istand:</B> a flag specifying whether or not to standardize the sill
of the semivariogram to the variance of the univariate distribution
(<B>istand=1</B> will standardize). It is essential that the variance of the
values of the initial random image matches the spatial (dispersion) variance
implied by the variogram model. That dispersion variance should be equal to
the total sill if it exists (i.e., a power model has not been used) and the
size of the field is much larger than the largest range in the variogram
model.
<LI><B>nst</B> and <B>c0:</B> the number of variogram structures and the
isotropic nugget constant
<LI>For each of the <B>nst</B> nested structures one must define <B>it</B>,
the type of structure; <B>cc</B>, the <I>c</I> parameter;
<B>ang1,ang2,ang3</B>, the angles defining the geometric anisotropy;
<B>aa_hmax</B>, the maximum horizontal range; <B>aa_hmin</B>, the minimum
horizontal range; and <B>aa_vert</B>, the vertical range. A detailed
description of these parameters is given in section II.3.
<LI>Indicator variograms follow the definition of the direct primary
variable variogram. </LI></UL></DT></DL><IMG height=8 alt=---
src="GSLIB Help SASIM.files/line.blue.gif" width=652>
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