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#* HISTORY *
#* B.Simon 24-Aug-94 Original
#* B.Simon 18-Sep-00 Revised search termination criterion
# GETMATCH -- Find rows in second table witch match rows in first
procedure getmatch (in1, in2, ncol, col1, col2, weight, nrow1, index1,
nrow2, index2, maxnorm, sphere, closest, dist)
pointer in1 # i: first table descriptor
pointer in2 # i: second table descriptor
int ncol # i: number of match columns
pointer col1[ARB] # i: match columns in first table
pointer col2[ARB] # i: match columns in second table
double weight[ARB] # i: weights used in computing norm
int nrow1 # i: number of rows in first table
int index1[ARB] # i: sorted row indices for first table
int nrow2 # i: number of rows in second table
int index2[ARB] # i: sorted row indices for second table
double maxnorm # i: maximum norm used in match
bool sphere # i: apply spherical correction to first column?
int closest[ARB] # o: closest match in second table to first
double dist[ARB] # o: distance between matched rows
#--
double sqnorm, proj, abnorm, norm, minabnorm, minnorm
int idx, jdx, irow, jrow, krow, jlast
begin
jlast = 1
sqnorm = maxnorm * maxnorm
# Find the row in the second table which minimizes the norm for
# each row of the first table
do idx = 1, nrow1 {
irow = index1[idx]
jrow = index2[jlast]
# The initial guess is the row which matched last time
call getnorm (in1, in2, ncol, col1, col2, irow, jrow,
weight, sphere, proj, abnorm, norm)
minabnorm = abnorm
minnorm = norm
krow = jrow
# Search backwards for a row which minimizes the norm
# Terminate the search when the first dimension of the norm (proj)
# is greater than the minimum norm, as all subsequent rows have
# norms that must be greater than the minimum
do jdx = jlast-1, 1, -1 {
jrow = index2[jdx]
call getnorm (in1, in2, ncol, col1, col2, irow, jrow,
weight, sphere, proj, abnorm, norm)
if (proj > minabnorm)
break
if (norm < minnorm) {
minabnorm = abnorm
minnorm = norm
krow = jrow
}
}
# Search forwards for a row that minimizes the norm
# Use the same termination condition as for the forwards search
do jdx = jlast+1, nrow2 {
jrow = index2[jdx]
call getnorm (in1, in2, ncol, col1, col2, irow, jrow,
weight, sphere, proj, abnorm, norm)
if (proj > minabnorm)
break
if (norm < minnorm) {
minabnorm = abnorm
minnorm = norm
krow = jrow
}
}
if (minnorm > sqnorm) {
dist[irow] = maxnorm
closest[irow] = 0
} else {
dist[irow] = sqrt (minnorm)
closest[irow] = krow
}
jlast = krow
}
end
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