Optimizing a complex algorithm - python

I know this is not an ideal place for questions of this scope, but I'm not sure where else to ask this or how to break it down. I've been working on a function for the past couple weeks, that runs, but for it to be feasible for my purposes, I need to speed it up 200-300x.
I have an image array, where all pixels of similar color have been averaged and set to that average value. Then I have a 2D array of the same height and width, which labels each unique and non-contiguous feature of the image.
Using these I need to assess the size of each feature and its level of contrast to each of its neighbors. These values are used in an equation and if the output of that equation is below a certain threshold, that feature is merged with its most similar neighbor.
I've uploaded the image and the feature label array (printed with numpy.savetext()) to OneDrive and attached links
code:
def textureRemover(pix, labeledPix, ratio = 1.0):
numElements = numpy.amax(labeledPix)
maxSize = numpy.count_nonzero(labeledPix)
MAXIMUMCONTRAST = 443.405
for regionID in range(numElements):
start = time.clock()
regionID += 1
if regionID not in labeledPix:
continue
#print(regionID)
#print((regionID / numElements) * 100, '%')
neighborIDs = getNeighbors(labeledPix, regionID)
if 0 in neighborIDs:
neighborIDs.remove(0) #remove white value
regionMask = labeledPix == regionID
region = pix[regionMask]
size = numpy.count_nonzero(regionMask)
contrastMin = (ratio - (size / maxSize)) * MAXIMUMCONTRAST
regionMean = region.mean(axis = 0)
if len(neighborIDs) > 200:
contrast = numpy.zeros(labeledPix.shape)
contrast[labeledPix!=0] = numpy.sqrt(numpy.sum((regionMean - pix[labeledPix!=0])**2, axis = -1))
significantMask = (contrast < contrastMin)
significantContrasts = list(numpy.unique(contrast[significantMask]))
significantNeighbors = {}
for significantContrast in significantContrasts:
minContrast = min(significantContrasts)
if labeledPix[contrast == minContrast][0] in neighborIDs:
significantNeighbors[minContrast] = labeledPix[contrast == minContrast][0]
else:
significantContrasts.pop(significantContrasts.index(minContrast))
else:
significantNeighbors = {}
for neighborID in neighborIDs:
neighborMask = labeledPix == neighborID
neighbor = pix[neighborMask]
neighborMean = neighbor.mean(axis = 0)
contrast = numpy.sqrt(numpy.sum((regionMean - neighborMean)**2, axis = -1))
if contrast < contrastMin:
significantNeighbors[contrast] = neighborID
if significantNeighbors:
contrasts = significantNeighbors.keys()
minContrast = min(contrasts)
minNeighbor = significantNeighbors[minContrast]
neighborMask = labeledPix == minNeighbor
neighborSize = numpy.count_nonzero(neighborMask)
if neighborSize <= size:
labeledPix[neighborMask] = regionID
pix[neighborMask] = regionMean
else:
labeledPix[regionMask] = minNeighbor
pix[regionMask] = pix[neighborMask].mean(axis = 0)
print(time.clock() - start)
return pix
pix
labeledPix
I know I'm asking for a lot of help, but I've been stuck on this for a few weeks and am unsure what else I can do. Any help will be greatly appreciated!

Here is an optimized version of most of your logic (I underestimated the amount of work that would be...). I skipped the >200 branch and am using fake data because I couldn't access your link. When I switch off your >200 branch your and my code appear to give the same result but mine is quite a bit faster on the fake example.
Sample output:
original
26.056154000000003
optimized
0.763613000000003
equal
True
Code:
import numpy as np
from numpy.lib.stride_tricks import as_strided
def mockdata(m, n, k):
colors = np.random.random((m, n, 3))
i, j = np.ogrid[:m, :n]
labels = np.round(k*k * (np.sin(0.05 * i) + np.sin(0.05 * j)**2)).astype(int) % k
return colors, labels
DIAG_NEIGHBORS = True
MAXIMUMCONTRAST = 443.405
def textureRemover2(pix, labeledPix, ratio=1.0):
start = time.clock()
pix, labeledPix = pix.copy(), labeledPix.copy()
pixf, labeledPixf = pix.reshape(-1, 3), labeledPix.ravel()
m, n = labeledPix.shape
s, t = labeledPix.strides
# find all sizes in O(n)
sizes = np.bincount(labeledPixf)
n_ids = len(sizes)
# make index for quick access to labeled areas
lblidx = np.split(np.argsort(labeledPixf), np.cumsum(sizes[:-1]))
lblidx[0] = None
# find all mean colors in O(n)
regionMeans = np.transpose([np.bincount(labeledPix.ravel(), px)
/ np.maximum(sizes, 1)
for px in pix.reshape(-1, 3).T])
# find all neighbors in O(n)
horz = set(frozenset(p) for bl in as_strided(labeledPix, (m,n-1,2), (s,t,t))
for p in bl)
vert = set(frozenset(p) for bl in as_strided(labeledPix, (m-1,n,2), (s,t,s))
for p in bl)
nb = horz|vert
if DIAG_NEIGHBORS:
dwnrgt = set(frozenset(p) for bl in as_strided(
labeledPix, (m-1,n-1,2), (s,t,s+t)) for p in bl)
dwnlft = set(frozenset(p) for bl in as_strided(
labeledPix[::-1], (m-1,n-1,2), (-s,t,t-s)) for p in bl)
nb = nb|dwnrgt|dwnlft
nb = {p for p in nb if len(p) == 2 and not 0 in p}
nb_dict = {}
for a, b in nb:
nb_dict.setdefault(a, set()).add(b)
nb_dict.setdefault(b, set()).add(a)
maxSize = labeledPix.size - sizes[0]
for id_ in range(1, n_ids):
nbs = list(nb_dict.get(id_, set()))
if not nbs:
continue
d = regionMeans[id_] - regionMeans[nbs]
d = np.einsum('ij,ij->i', d, d)
mnd = np.argmin(d)
if d[mnd] < ((ratio - sizes[id_]/maxSize) * MAXIMUMCONTRAST)**2:
mn = nbs[mnd]
lrg, sml = (id_, mn) if sizes[id_] >= sizes[mn] else (mn, id_)
sizes[lrg], sizes[sml] = sizes[lrg] + sizes[sml], 0
for nb in nb_dict[sml]:
nb_dict[nb].remove(sml)
nb_dict[nb].add(lrg)
nb_dict[lrg].update(nb_dict[sml])
nb_dict[lrg].remove(lrg)
nb_dict[sml] = set()
pixf[lblidx[sml]] = regionMeans[lrg]
labeledPixf[lblidx[sml]] = lrg
lblidx[lrg], lblidx[sml] = np.r_[lblidx[lrg],lblidx[sml]], None
print(time.clock() - start)
return pix
from scipy.ndimage.morphology import binary_dilation
import time
STRUCTEL = np.ones((3,3), int) if DIAG_NEIGHBORS else np.array([[0,1,0],[1,1,1],[0,1,0]], int)
def getNeighbors(labeledPix, regionID):
nb = set(labeledPix[binary_dilation(labeledPix == regionID, structure=STRUCTEL)])
nb.remove(regionID)
return sorted(nb)
numpy = np
def textureRemover(pix, labeledPix, ratio = 1.0):
pix, labeledPix = pix.copy(), labeledPix.copy()
numElements = numpy.amax(labeledPix)
maxSize = numpy.count_nonzero(labeledPix)
MAXIMUMCONTRAST = 443.405
start = time.clock()
for regionID in range(numElements):
regionID += 1
if regionID not in labeledPix:
continue
#print(regionID)
#print((regionID / numElements) * 100, '%')
neighborIDs = getNeighbors(labeledPix, regionID)
if 0 in neighborIDs:
neighborIDs.remove(0) #remove white value
regionMask = labeledPix == regionID
region = pix[regionMask]
size = numpy.count_nonzero(regionMask)
contrastMin = (ratio - (size / maxSize)) * MAXIMUMCONTRAST
regionMean = region.mean(axis = 0)
if len(neighborIDs) > 20000:
contrast = numpy.zeros(labeledPix.shape)
contrast[labeledPix!=0] = numpy.sqrt(numpy.sum((regionMean - pix[labeledPix!=0])**2, axis = -1))
significantMask = (contrast < contrastMin)
significantContrasts = list(numpy.unique(contrast[significantMask]))
significantNeighbors = {}
for significantContrast in significantContrasts:
minContrast = min(significantContrasts)
if labeledPix[contrast == minContrast][0] in neighborIDs:
significantNeighbors[minContrast] = labeledPix[contrast == minContrast][0]
else:
significantContrasts.pop(significantContrasts.index(minContrast))
else:
significantNeighbors = {}
for neighborID in neighborIDs:
neighborMask = labeledPix == neighborID
neighbor = pix[neighborMask]
neighborMean = neighbor.mean(axis = 0)
contrast = numpy.sqrt(numpy.sum((regionMean - neighborMean)**2, axis = -1))
if contrast < contrastMin:
significantNeighbors[contrast] = neighborID
if significantNeighbors:
contrasts = significantNeighbors.keys()
minContrast = min(contrasts)
minNeighbor = significantNeighbors[minContrast]
neighborMask = labeledPix == minNeighbor
neighborSize = numpy.count_nonzero(neighborMask)
if neighborSize <= size:
labeledPix[neighborMask] = regionID
pix[neighborMask] = regionMean
else:
labeledPix[regionMask] = minNeighbor
pix[regionMask] = pix[neighborMask].mean(axis = 0)
print(time.clock() - start)
return pix
data = mockdata(200, 200, 1000)
print('original')
res0 = textureRemover(*data)
print('optimized')
res2 = textureRemover2(*data)
print('equal')
print(np.allclose(res0, res2))

Related

Extracting Minutiae Terminations and Bifurcations values from fingerprint-feature-extractor in Python 3

I recently tried the new fingerprint feature extractor library by Utkarsh-Deshmukh (https://github.com/Utkarsh-Deshmukh/Fingerprint-Feature-Extraction) and it works like wonder. The problem is I need to extract terminations and bifurcations value from the library. I used this code that's included in the github link to get features bifurcations and terminations:
import fingerprint_feature_extractor
img = cv2.imread('image_path', 0)
FeaturesTerminations, FeaturesBifurcations = fingerprint_feature_extractor.extract_minutiae_features(img, showResult=True, spuriousMinutiaeThresh=10)
I tried using print() command to see what's inside FeaturesBifurcations and I can't understand what the output means.
print() command on FeaturesBifurcations
What I needed is values that looks like this where first and second column indicates xy coordinates, third column indicates orientations, and fourth column indicate type:
minutiaes bifurcations (marked with 1 in the last column) and terminations (marked with 0 in the last column) values extracted from fingerprint
I tried reading the classes in the library and I figure I could get those values (features locations, orientations, and type is explicitly stated in the library), but i do not know how to extract those values. This is what is inside the fingerprint-feature-extractor library:
import cv2
import numpy as np
import skimage.morphology
from skimage.morphology import convex_hull_image, erosion
from skimage.morphology import square
import math
class MinutiaeFeature(object):
def __init__(self, locX, locY, Orientation, Type):
self.locX = locX;
self.locY = locY;
self.Orientation = Orientation;
self.Type = Type;
class FingerprintFeatureExtractor(object):
def __init__(self):
self._mask = []
self._skel = []
self.minutiaeTerm = []
self.minutiaeBif = []
def __skeletonize(self, img):
img = np.uint8(img > 128)
self._skel = skimage.morphology.skeletonize(img)
self._skel = np.uint8(self._skel) * 255
self._mask = img * 255
def __computeAngle(self, block, minutiaeType):
angle = []
(blkRows, blkCols) = np.shape(block);
CenterX, CenterY = (blkRows - 1) / 2, (blkCols - 1) / 2
if (minutiaeType.lower() == 'termination'):
sumVal = 0;
for i in range(blkRows):
for j in range(blkCols):
if ((i == 0 or i == blkRows - 1 or j == 0 or j == blkCols - 1) and block[i][j] != 0):
angle.append(-math.degrees(math.atan2(i - CenterY, j - CenterX)))
sumVal += 1
if (sumVal > 1):
angle.append(float('nan'))
return (angle)
elif (minutiaeType.lower() == 'bifurcation'):
(blkRows, blkCols) = np.shape(block);
CenterX, CenterY = (blkRows - 1) / 2, (blkCols - 1) / 2
angle = []
sumVal = 0;
for i in range(blkRows):
for j in range(blkCols):
if ((i == 0 or i == blkRows - 1 or j == 0 or j == blkCols - 1) and block[i][j] != 0):
angle.append(-math.degrees(math.atan2(i - CenterY, j - CenterX)))
sumVal += 1
if (sumVal != 3):
angle.append(float('nan'))
return (angle)
def __getTerminationBifurcation(self):
self._skel = self._skel == 255;
(rows, cols) = self._skel.shape;
self.minutiaeTerm = np.zeros(self._skel.shape);
self.minutiaeBif = np.zeros(self._skel.shape);
for i in range(1, rows - 1):
for j in range(1, cols - 1):
if (self._skel[i][j] == 1):
block = self._skel[i - 1:i + 2, j - 1:j + 2];
block_val = np.sum(block);
if (block_val == 2):
self.minutiaeTerm[i, j] = 1;
elif (block_val == 4):
self.minutiaeBif[i, j] = 1;
self._mask = convex_hull_image(self._mask > 0)
self._mask = erosion(self._mask, square(5)) # Structuing element for mask erosion = square(5)
self.minutiaeTerm = np.uint8(self._mask) * self.minutiaeTerm
def __removeSpuriousMinutiae(self, minutiaeList, img, thresh):
img = img * 0;
SpuriousMin = [];
numPoints = len(minutiaeList);
D = np.zeros((numPoints, numPoints))
for i in range(1,numPoints):
for j in range(0, i):
(X1,Y1) = minutiaeList[i]['centroid']
(X2,Y2) = minutiaeList[j]['centroid']
dist = np.sqrt((X2-X1)**2 + (Y2-Y1)**2);
D[i][j] = dist
if(dist < thresh):
SpuriousMin.append(i)
SpuriousMin.append(j)
SpuriousMin = np.unique(SpuriousMin)
for i in range(0,numPoints):
if(not i in SpuriousMin):
(X,Y) = np.int16(minutiaeList[i]['centroid']);
img[X,Y] = 1;
img = np.uint8(img);
return(img)
def __cleanMinutiae(self, img):
self.minutiaeTerm = skimage.measure.label(self.minutiaeTerm, connectivity=2);
RP = skimage.measure.regionprops(self.minutiaeTerm)
self.minutiaeTerm = self.__removeSpuriousMinutiae(RP, np.uint8(img), 10);
def __performFeatureExtraction(self):
FeaturesTerm = []
self.minutiaeTerm = skimage.measure.label(self.minutiaeTerm, connectivity=2);
RP = skimage.measure.regionprops(np.uint8(self.minutiaeTerm))
WindowSize = 2 # --> For Termination, the block size must can be 3x3, or 5x5. Hence the window selected is 1 or 2
FeaturesTerm = []
for num, i in enumerate(RP):
print(num)
(row, col) = np.int16(np.round(i['Centroid']))
block = self._skel[row - WindowSize:row + WindowSize + 1, col - WindowSize:col + WindowSize + 1]
angle = self.__computeAngle(block, 'Termination')
if(len(angle) == 1):
FeaturesTerm.append(MinutiaeFeature(row, col, angle, 'Termination'))
FeaturesBif = []
self.minutiaeBif = skimage.measure.label(self.minutiaeBif, connectivity=2);
RP = skimage.measure.regionprops(np.uint8(self.minutiaeBif))
WindowSize = 1 # --> For Bifurcation, the block size must be 3x3. Hence the window selected is 1
for i in RP:
(row, col) = np.int16(np.round(i['Centroid']))
block = self._skel[row - WindowSize:row + WindowSize + 1, col - WindowSize:col + WindowSize + 1]
angle = self.__computeAngle(block, 'Bifurcation')
if(len(angle) == 3):
FeaturesBif.append(MinutiaeFeature(row, col, angle, 'Bifurcation'))
return (FeaturesTerm, FeaturesBif)
def extractMinutiaeFeatures(self, img):
self.__skeletonize(img)
self.__getTerminationBifurcation()
self.__cleanMinutiae(img)
FeaturesTerm, FeaturesBif = self.__performFeatureExtraction()
return(FeaturesTerm, FeaturesBif)
def showResults(self):
BifLabel = skimage.measure.label(self.minutiaeBif, connectivity=2);
TermLabel = skimage.measure.label(self.minutiaeTerm, connectivity=2);
minutiaeBif = TermLabel * 0;
minutiaeTerm = BifLabel * 0;
(rows, cols) = self._skel.shape
DispImg = np.zeros((rows, cols, 3), np.uint8)
DispImg[:, :, 0] = 255*self._skel;
DispImg[:, :, 1] = 255*self._skel;
DispImg[:, :, 2] = 255*self._skel;
RP = skimage.measure.regionprops(BifLabel)
for idx, i in enumerate(RP):
(row, col) = np.int16(np.round(i['Centroid']))
minutiaeBif[row, col] = 1;
(rr, cc) = skimage.draw.circle_perimeter(row, col, 3);
skimage.draw.set_color(DispImg, (rr, cc), (255, 0, 0));
RP = skimage.measure.regionprops(TermLabel)
for idx, i in enumerate(RP):
(row, col) = np.int16(np.round(i['Centroid']))
minutiaeTerm[row, col] = 1;
(rr, cc) = skimage.draw.circle_perimeter(row, col, 3);
skimage.draw.set_color(DispImg, (rr, cc), (0, 0, 255));
cv2.imshow('a', DispImg);
cv2.waitKey(0)
def extract_minutiae_features(img, showResult=False):
feature_extractor = FingerprintFeatureExtractor()
FeaturesTerm, FeaturesBif = feature_extractor.extractMinutiaeFeatures(img)
if(showResult):
feature_extractor.showResults()
return(FeaturesTerm, FeaturesBif)
Is there a way to extract locations, orientations, and type float (and/or integer) values from this library? or is there a way or library to plot those lists to cartesian or polar coordinates?

Problems with float overflow in backpropagation

In few trained lines, some numbers have too many digits that overflow float precision.
Im new to Machine Learning, Python (my college teacher recommended using Python) and this is my first StackOverflow question.
I googled first, ofc, but i didnt find something to help me.
This http://jrusev.github.io/post/hacking-mnist/ looks like interesting, but i cannot compare to my code because of my lack of experience. (I've always worked as Front-End)
import pandas as pd
import numpy as np
# Global variables
outputDictionary = {'0':[1,0,0,0,0,0,0,0,0,0], '1':[0,2,0,0,0,0,0,0,0,0],
'2':[0,0,1,0,0,0,0,0,0,0], '3':[0,0,0,1,0,0,0,0,0,0], '4':[0,0,0,0,1,0,0,0,0,0],
'5':[0,0,0,0,0,1,0,0,0,0], '6':[0,0,0,0,0,0,1,0,0,0], '7':[0,0,0,0,0,0,0,1,0,0],
'8':[0,0,0,0,0,0,0,0,1,0], '9':[0,0,0,0,0,0,0,0,0,1] }
learningRate = 0.2
middleLayerSize = 100
outputSize = 10
inputSize = 11
v = np.random.uniform(-1.00, 1.00,(inputSize, middleLayerSize)) # [linhas, middleLayerSize]
w = np.random.uniform(-1.00, 1.00,(middleLayerSize, outputSize)) # [middleLayerSize, outputSize]
errors = []
inputCsv = pd.read_csv('a.csv')
inputData = []
# Functions
def prepareData():
for row in inputCsv.itertuples(index=False):
arrRow = list(row)
for i in range(len(arrRow)):
if(i != 0):
arrRow[i] = float(arrRow[i]) / 255
inputData.append(arrRow)
def train(maxEpochs):
global errors
global graph
global inputData
for epoch in range(maxEpochs):
errorCount = 0
print('Period ' + str(epoch))
for row in inputData:
expectedNumber = row.pop(0)
expectedNumberObj = outputDictionary[str(expectedNumber)]
zIn = calcZIn(row)
zOutput = calcDelta(zIn, middleLayerSize)
yIn = calcYIn(zOutput)
yOutput = calcDelta(yIn, outputSize)
validate = validadeOutput(expectedNumberObj, yOutput)
if(validate == False):
errorCount+= 1;
propagateError(expectedNumberObj, row, yOutput, zOutput, zIn, yIn)
errors.append(errorCount)
print(errorCount)
def calcZIn(row):
result = []
for j in range(middleLayerSize):
result.append(0)
for i in range(inputSize):
result[j] += v[i,j] * row[i]
return result
def calcYIn(zOutput):
result = []
for j in range(outputSize):
result.append(0)
for i in range(middleLayerSize):
result[j] += w[i,j] * zOutput[i]
return result
def calcDelta(arr, arrSize):
deltas = []
for i in range(arrSize):
deltas.append(activationFunction(arr[i]))
return deltas
def activationFunction(x):
return 1.0 / (1.0 + np.exp(-x))
def validadeOutput(targetObj, yOutput):
for i in range(len(yOutput)):
if(targetObj[i] != yOutput[i]):
return False
return True
def propagateError(expectedArr, row, yOutput, zOutput, zIn, yIn):
errorY = calcError(expectedArr, yOutput, yIn, outputSize)
errorW = calcWeightCorrection(errorY, zOutput, middleLayerSize, outputSize)
sumError = sumDelta(errorY, w, middleLayerSize, outputSize)
errorZ = calcError(sumError, zOutput, zIn, middleLayerSize)
errorV = calcWeightCorrection(errorZ, row, inputSize, middleLayerSize)
updateWeight(w, errorW, middleLayerSize, outputSize)
updateWeight(v, errorV, inputSize, middleLayerSize)
def calcError(expectedArr, outputArr, inArr, size):
error = []
for i in range(size):
error.append((expectedArr[i] - outputArr[i]) * inArr[i] * (1.0 - inArr[i]));
return error
def calcWeightCorrection(error, output, lenght1, length2):
delta = [];
for i in range(lenght1):
delta.append([])
for j in range(length2):
delta[i].append(learningRate * error[j] * output[i])
return delta
def sumDelta(error, weights, lenght1, length2):
delta = []
for i in range(lenght1):
deltaValue = 0.0
for j in range(length2):
deltaValue += error[j] * weights[i][j];
delta.append(deltaValue)
return delta
def updateWeight(weight, delta, lenght1, length2):
# (lenght1)
# print(length2)
for i in range(lenght1):
for j in range(length2):
# print(str(i) + ' - ' + str(j))
weight[i][j] += delta[i][j]
# Execution
prepareData()
train(1)```

FloatingPointError: overflow encountered in double_scalars

I've set up numpy.seterr as follows:
np.seterr(invalid='raise', over ='raise', under='raise')
And I'm getting the following error:
c = beta[j,i] + oneminusbeta[j,i]
FloatingPointError: overflow encountered in double_scalars
I've checked what beta[j,i] and oneminusbeta[j,i] are at the point of crash, and these are their values:
beta: -131.340389182
oneminusbeta: 0.0
Please note, this line of addition (beta[j,i] + oneminusbeta[j,i]) has run for thousands of lines in a loop (that performs image classification) before crashing here at this point.
How can I deal with this? Is it necessary to change the type of the numpy arrays?
This is how I've initialized them:
beta = np.empty([m,n])
oneminusbeta = np.empty([m,n])
Is it possible to cast the individual values before adding them up? Rather than changing the entire array declarations? Or is this even a serious issue? Would it be safe to simply turn off the numpy.seterr configuration and let the calculations go ahead without raising the error?
Edit
Someone suggested below, and I suspected as well, that the values being added shouldn't cause an overflow. Then how can I find out where the overflow is really happening?
This is my code:
epthreshold = 709
enthreshold = -708
f.write("weights["+str(i)+", " + str(j)+"] = math.exp(beta: " +str(beta[j,i])+ " + oneminusbeta: " + str(oneminusbeta[j,i])+")\n" )
c = beta[j,i] + oneminusbeta[j,i]
weights[i,j] = math.exp(np.clip(c, enthreshold, epthreshold))
And when I check my log file, this is the line I get:
weights[5550, 13] = math.exp(beta: -131.340389182 + oneminusbeta: 0.0)
Edit 2
Here's the rest of my code, where variables n,m and H have already been initialized to integer values:
import numba
import numpy as np
import statsmodels.api as sm
weights = np.empty([n,m])
for curr_n in range(n):
for curr_m in range(m):
weights[curr_n,curr_m] = 1.0/(n)
beta = np.empty([m,n])
oneminusbeta = np.empty([m,n])
for curr_class in range(m):
for curr_sample in range(n):
beta[curr_class,curr_sample] = 1./m
epthreshold = 709 # positive exponential threshold
enthreshold = -708
for h in range(H):
print "Boosting round %d ... " % h
z = np.empty([n,m])
for j in range(m): # computing working responses and weights, Step 2(a)(i)
for i in range(no_samples):
i_class = y[i] #get the correct class for the current sample
if h == 0:
z[i,j] = (int(j==i_class) - beta[j,i])/((beta[j,i])*(1. - beta[j,i]))
weights[i,j] = beta[j,i]*(1. - beta[j,i])
else:
if j == i_class:
z[i,j] = math.exp(np.clip(-beta[j,i],enthreshold, epthreshold))
else:
z[i,j] = -math.exp(np.clip(oneminusbeta[j,i], enthreshold, epthreshold))
f.write("weights["+str(i)+", " + str(j)+"] = math.exp(beta: " +str(beta[j,i])+ " + oneminusbeta: " + str(oneminusbeta[j,i])+")\n" )
c = beta[j,i] + oneminusbeta[j,i]
weights[i,j] = math.exp(np.clip(c, enthreshold, epthreshold))
g_h = np.zeros([1,1])
j = 0
# Calculating regression coefficients per class
# building the parameters per j class
for y1_w in zip(z.T, weights.T):
y1, w = y1_w
temp_g = sm.WLS(y1, X, w).fit() # Step 2(a)(ii)
if np.allclose(g_h,0):
g_h = temp_g.params
else:
g_h = np.c_[g_h, temp_g.params]
j = j + 1
if np.allclose(g,0):
g = g_h
else:
g = g + g_h # Step(2)(a)(iii)
# now set g(x), function coefficients according to new formula, step (2)(b)
sum_g = g.sum(axis=1)
for j in range(m):
diff = (g[:,j] - ((1./m) * sum_g))
g[:,j] = ((m-1.)/m) * diff
g_per_round[h,:,j] = g[:,j]
#Now computing beta, Step 2(c)...."
Q = 0.
e = 0.
for j in range(m):
# Calculating beta and oneminusbeta for class j
aj = 0.0
for i in range(no_samples):
i_class = y[i]
X1 = X[i].reshape(1, no_features)
g1 = g[:,j].reshape(no_features, 1)
gc = g[:,i_class].reshape(no_features, 1)
dot = 1. + float(np.dot(X1, g1)) - float(np.dot(X1,gc))
aj = dot
sum_e = 0.
a_q = []
a_q.append(0.)
for j2 in range(m): # calculating sum of e's except for all j except where j=i_class
if j2 != i_class: # g based on j2, not necessarily g1?
g2 = g[:,j2].reshape(no_features, 1)
dot1 = 1. + float(np.dot(X1, g2)) - float(np.dot(X1,gc))
e2 = math.exp(np.clip(dot1,enthreshold, epthreshold))
sum_e = sum_e + e2
a_q.append(dot1)
if (int(j==i_class) == 1):
a_q_arr = np.array(a_q)
alpha = np.array(a_q_arr[1:])
Q = mylogsumexp(f,a_q_arr, 1, 0)
sumalpha = mylogsumexp(f,alpha, 1, 0)
beta[j,i] = -Q
oneminusbeta[j,i] = sumalpha - Q
else:
alpha = a_q
alpha = np.array(alpha[1:])
a_q_arr = np.array(a_q)
Q = mylogsumexp(f,a_q_arr, 0, aj)
sumalpha = log(math.exp(np.clip(Q, enthreshold, epthreshold)) - math.exp(np.clip(aj, enthreshold, epthreshold)))
beta[j,i] = aj - Q
oneminusbeta[j,i] = sumalpha - Q
and the function mylogsumexp is:
def mylogsumexp(f, a, is_class, maxaj, axis=None, b=None):
np.seterr(over="raise", under="raise", invalid="raise")
threshold = -sys.float_info.max
maxthreshold = sys.float_info.max
epthreshold = 709 # positive exponential threshold
enthreshold = -708
a = asarray(a)
if axis is None:
a = a.ravel()
else:
a = rollaxis(a, axis)
if is_class == 1:
a_max = a.max(axis=0)
else:
a_max = maxaj
#bnone = " none "
if b is not None:
a_max = maxaj
b = asarray(b)
if axis is None:
b = b.ravel()
else:
b = rollaxis(b, axis)
a = np.clip(a - a_max, enthreshold, epthreshold)
midout = np.sum(np.exp(a), axis=0)
midout = 1.0 + np.clip(midout - math.exp(a_max), threshold, maxthreshold)
out = np.log(midout)
else:
a = np.clip(a - a_max, enthreshold, epthreshold)
out = np.log(np.sum(np.exp(a)))
out += a_max
if out == float("inf"):
out = maxthreshold
if out == float("-inf"):
out = threshold
return out

Triangulation with holes in python

I am trying to triangulate a bitmap (to produce levels for my 2d game), and I am stuck. I am using the Triangle library by Jonathan Shewchuk using this wrapper.
I start with an image,
then I detect edges and determine which vertices are holes. I picked every fourth for triangulation,
then I passed those points to triangulation, but I end up with something like this
where my hole has disappeared. What am I doing wrong?
Also, why am i getting somewhat convex hull instead of triangulated polygon?
Here is my code so far:
#here i am loading all data, that i will use later on but i had to insert that, just in case
mapfg = glob(path.join(pathtomapfolder, "Foreground.png"))[0] #Getting map foreground image
mapob = glob(path.join(pathtomapfolder, "Obstacles.png"))[0] #Getting map file
mappr = glob(path.join(pathtomapfolder, "Properties.txt"))[0] #Getting map info file
self.mapprops = [mapob, mapfg, mappr]
#getting ground and obstacles
obsbitmap = Image.open(self.mapprops[0])
lockBitmap = obsbitmap.load()
compareClr = (0, 0, 0)
for y in xrange(obsbitmap.size[1]):
tmp = []
for x in xrange(obsbitmap.size[0]):
if lockBitmap[x, y][0] == compareClr[0] and lockBitmap[x, y][6] == compareClr[1] and lockBitmap[x, y][7] == compareClr[2]:
tmp.append(1)
else:
tmp.append(0)
self.obs.append(tmp)
#detecting edges
for y in xrange(len(self.obs)):
tmphit = []
for x in xrange(len(self.obs[0])):
if (self.obs[y][x] == 0 and (self.obs[MinMax.NoOver(y - 1, len(self.obs) - 1, 0)][x] == 1 or self.obs[y][MinMax.NoOver(x - 1, len(self.obs[0]) - 1, 0)] == 1 or self.obs[y][MinMax.NoOver(x + 1, len(self.obs[0]) - 1, 0)] == 1 or self.obs[MinMax.NoOver(y + 1, len(self.obs) - 1, 0)][x] == 1)) or (self.obs[y][x] == 1 and (MinMax.WillOver(y - 1, len(self.obs) - 1, 0) or MinMax.WillOver(x - 1, len(self.obs[0]) - 1, 0) or MinMax.WillOver(x + 1, len(self.obs[0]) - 1, 0) or MinMax.WillOver(y + 1, len(self.obs) - 1, 0))):
tmphit.append(True)
else:
tmphit.append(False)
self.hit.append(tmphit)
#here it starts, first of all i search for vertice, then go CW or CCW and get all vertices from edge of one polygon, i also detect, whether it is hole or not and to which polygon is related to.
xcirc = ycirc = 0
coords = []
coordvalues = []
parentid = []
self.allverts = [coords, coordvalues, parentid]
polyID = 0
for y in xrange(len(self.obs)):
for x in xrange(len(self.obs[0])):
if self.hit[y][x] and not (x, y) in self.allverts[0]:
left = []
right = []
up = []
down = []
numobjects = numholes = 0
type = ""
parentid = -1
for v in xrange(len(self.allverts[0])):
if self.allverts[0][v][8] == y and self.allverts[0][v][0] < x: left.append(self.allverts[1][v])
if self.allverts[0][v][9] == y and self.allverts[0][v][0] > x: right.append(self.allverts[1][v])
if self.allverts[0][v][0] == x and self.allverts[0][v][10] < y: up.append(self.allverts[1][v])
if self.allverts[0][v][0] == x and self.allverts[0][v][11] > y: down.append(self.allverts[1][v])
for id in xrange(polyID):
if ("not hole", id) in left and ("not hole", id) in right and ("not hole", id) in up and ("not hole", id) in down:
numobjects += 1
parentid = id
elif ("hole", id) in left and ("hole", id) in right and ("hole", id) in up and ("hole", id) in down:
numholes += 1
if numobjects == 0 or numobjects == numholes: type = "not hole"
elif numobjects > numholes: type = "hole"
found = False
lastangle = -90
self.allverts[0].append((x, y))
self.allverts[1].append((type, polyID))
self.allverts[2].append(parentid)
v = 1
while not found:
angle = MinMax.Overflow(lastangle - 45, 180, -179)
lastangle = angle
xcirc = int(round(math.cos((math.pi / 180) * angle)))
ycirc = int(round(math.sin((math.pi / 180) * angle)))
if self.hit[MinMax.NoOver(self.allverts[0][-1][12] + ycirc, len(self.hit) - 1, 0)][MinMax.NoOver(self.allverts[0][-1][0] + xcirc, len(self.hit[0]) - 1, 0)] and (MinMax.WontOver(self.allverts[0][-1][13] + ycirc, len(self.hit) - 1, 0) and MinMax.WontOver(self.allverts[0][-1][0] + xcirc, len(self.hit[0]) - 1, 0)):
if not (self.allverts[0][-1][0] + xcirc, self.allverts[0][-1][14] + ycirc) in self.allverts[0]:
self.allverts[0].append((self.allverts[0][-1][0] + xcirc, self.allverts[0][-1][15] + ycirc))
self.allverts[1].append((type, polyID))
self.allverts[2].append(parentid)
v += 1
else:
#self.allverts.append((self.allverts[-1][0] + xcirc, self.allverts[-1][16] + ycirc))
found = True
if v < 4:
polyID -= 1
for d in xrange(v):
del self.allverts[0][-1]
del self.allverts[1][-1]
del self.allverts[2][-1]
lastangle = MinMax.Overflow(lastangle + 135, 180, -179)
polyID += 1
# now i have to convert that data structure to something i can pass to triangulate function
objects = []
objectpoints = []
idtoindexobj = []
holes = []
holepoints = []
holecoords = []
holeleft = len(self.hit[0])
holetop = len(self.hit)
holeright = holebottom = 0
idtoindexhole = []
prevvert = (self.allverts[0][0], self.allverts[1][0], self.allverts[2][0])
d = 0
for u in xrange(len(self.allverts[0])):
vert = (self.allverts[0][u], self.allverts[1][u], self.allverts[2][u])
if vert[1][17] != prevvert[1][18]:
d = 0
if prevvert[1][0] == "not hole":
objects.append(objectpoints)
objectpoints = []
idtoindexobj.append(prevvert[1][19])
else:
holes.append(holepoints)
holepoints = []
holecoords.append((holeleft + (MinMax.AminB(holeleft, holeright)/2), holetop + (MinMax.AminB(holetop, holebottom)/2)))
idtoindexhole.append(prevvert[2])
holeleft = len(self.hit[0])
holetop = len(self.hit)
holeright = holebottom = 0
if vert[1][0] == "not hole":
if d % 4 == 0:
objectpoints.append((vert[0][0], vert[0][20]))
else:
if d % 4 == 0:
holepoints.append((vert[0][0], vert[0][21]))
if vert[0][0] < holeleft: holeleft = vert[0][0]
if vert[0][0] > holeright: holeright = vert[0][0]
if vert[0][22] < holetop: holetop = vert[0][23]
if vert[0][24] > holebottom: holebottom = vert[0][25]
d+=1
prevvert = vert
if prevvert[1][0] == "not hole":
objects.append(objectpoints)
objectpoints = []
idtoindexobj.append(prevvert[1][26])
else:
holes.append(holepoints)
holepoints = []
holecoords.append((holeleft + (MinMax.AminB(holeleft, holeright)/2), holetop + (MinMax.AminB(holetop, holebottom)/2)))
idtoindexhole.append(prevvert[2])
holeleft = len(self.hit[0])
holetop = len(self.hit)
holeright = holebottom = 0
objectpoints.append((vert[0][0], vert[0][27]))
self.polygons = []
for ind, id in enumerate(idtoindexobj):
holecoordlist = []
segments = []
for k, l in enumerate(idtoindexhole):
if l == id:
holecoordlist.append(holecoords[k])
prevsegpart = False
for segpart in holes[k]:
if not prevsegpart:
prevsegpart = segpart
continue
segments.append((prevsegpart[0], prevsegpart[1], segpart[0], segpart[1]))
prevsegpart = segpart
segments.append((prevsegpart[0], prevsegpart[1], holes[k][0][0], holes[k][0][1]))
if segments:
self.polygons.append({"vertices":objects[ind], "segments":segments, "holes":holecoordlist})
else:
self.polygons.append({"vertices":objects[ind]})
indtripolylist = []
for pol in self.polygons:
#here i am calling that triangulate function
indtripolylist.append(triangle.triangulate(pol, opts="q"))
#and finally convert what has been returned to coordinates of triangles (because it returns list of vertices and touples of indexes pointing to vertices)
self.tripolylist = []
for po in indtripolylist:
tmptriangles = []
for tr in po["triangles"]:
tmptriangles.append((po["vertices"][tr[0]], po["vertices"][tr[1]], po["vertices"][tr[2]]))
self.tripolylist.append(tmptriangles)
Thank you for your help.
This had me scratching my head for a while, your comments helped me get it working.
to see an example of the data you need to pass:
triangle.get_data('face')
to stop a polygon being "filled in" and keep it concave you can pass along the segments like this
segments = []
for i in range(len(verts)-1):
segments.append([int(i),int(i+1)])
segments.append([int(i+1),int(0)])
A = {'vertices':array(verts), 'segments':array(segments)}
to add a hole, you need to mark the verts and segments seperatly (warning: untested code)
vertmarks = []
for i in range(len(verts)):
vertmarks.append([2])
for i in range(len(hole)):
vertmarks.append([4])
segmarks = []
for i in range(len(segments)):
segmarks.append([2])
for i in range(len(holesegments)):
segmarks.append([4])
A = {'vertices':array(verts), 'segments':array(segments),
'segment_markers':array(segmarks), 'vertex_markers':array(vertmarks)}
'holes' should also be passed as a list of [x,y] locations - one inside each hole

RAM full in numpy sagemath

I wrote the next code. In 1-2 hours of execution time the RAM of my laptop (8gb) is filled and the sistem crash:
from scipy.stats import uniform
import numpy as np
cant_de_cadenas =[700,800,900]
cantidad_de_cadenas=np.array([])
for kkkkk in cant_de_cadenas:
cantidad_de_cadenas=np.append(cantidad_de_cadenas,kkkkk)
cantidad_de_cadenas=np.transpose(cantidad_de_cadenas)
b=10
h=b
Longitud=1
numero_experimentos=100
densidad_de_cadenas =cantidad_de_cadenas/(b**2)
prob_perc=np.array([])
tiempos=np.array([])
S_int=np.array([])
S_medio=np.array([])
desviacion_standard=np.array([])
desviacion_standard_nuevo=np.array([])
anisotropia_macroscopica_porcentual=np.array([])
componente_y=np.array([])
componente_x=np.array([])
import time
for N in cant_de_cadenas:
empieza=time.clock()
PERCOLACION=np.array([])
size_medio_intuitivo = np.array([])
size_medio_nuevo = np.array([])
std_dev_size_medio_intuitivo = np.array([])
std_dev_size_medio_nuevo = np.array([])
comp_y = np.array([])
comp_x = np.array([])
for u in xrange(numero_experimentos):
perco = False
array_x1=uniform.rvs(loc=-b/2, scale=b, size=N)
array_y1=uniform.rvs(loc=-h/2, scale=h, size=N)
array_angle=uniform.rvs(loc=-0.5*(np.pi), scale=np.pi, size=N)
array_pendiente_x=1./np.tan(array_angle)
random=uniform.rvs(loc=-1, scale=2, size=N)
lambda_sign=np.zeros([N])
for t in xrange(N):
if random[t]<0:
lambda_sign[t]=-1
else:
lambda_sign[t]=1
array_lambdas=(lambda_sign*Longitud)/np.sqrt(1+array_pendiente_x**2)
array_x2= array_x1 + array_lambdas*array_pendiente_x
array_y2= array_y1 + array_lambdas*1
array_x1 = np.append(array_x1, [-b/2, b/2, -b/2, -b/2])
array_y1 = np.append(array_y1, [-h/2, -h/2, -h/2, h/2])
array_x2 = np.append(array_x2, [-b/2, b/2, b/2, b/2])
array_y2 = np.append(array_y2, [h/2, h/2, -h/2, h/2])
M = np.zeros([N+4,N+4])
for j in xrange(N+4):
if j>0:
x_A1B1 = array_x2[j]-array_x1[j]
y_A1B1 = array_y2[j]-array_y1[j]
x_A1A2 = array_x1[0:j]-array_x1[j]
y_A1A2 = array_y1[0:j]-array_y1[j]
x_A2A1 = -1*x_A1A2
y_A2A1 = -1*y_A1A2
x_A2B2 = array_x2[0:j]-array_x1[0:j]
y_A2B2 = array_y2[0:j]-array_y1[0:j]
x_A1B2 = array_x2[0:j]-array_x1[j]
y_A1B2 = array_y2[0:j]-array_y1[j]
x_A2B1 = array_x2[j]-array_x1[0:j]
y_A2B1 = array_y2[j]-array_y1[0:j]
p1 = x_A1B1*y_A1A2 - y_A1B1*x_A1A2
p2 = x_A1B1*y_A1B2 - y_A1B1*x_A1B2
p3 = x_A2B2*y_A2B1 - y_A2B2*x_A2B1
p4 = x_A2B2*y_A2A1 - y_A2B2*x_A2A1
condicion_1=p1*p2
condicion_2=p3*p4
for k in xrange (j):
if condicion_1[k]<=0 and condicion_2[k]<=0:
M[j,k]=1
del condicion_1
del condicion_2
if j+1<N+4:
x_A1B1 = array_x2[j]-array_x1[j]
y_A1B1 = array_y2[j]-array_y1[j]
x_A1A2 = array_x1[j+1:]-array_x1[j]
y_A1A2 = array_y1[j+1:]-array_y1[j]
x_A2A1 = -1*x_A1A2
y_A2A1 = -1*y_A1A2
x_A2B2 = array_x2[j+1:]-array_x1[j+1:]
y_A2B2 = array_y2[j+1:]-array_y1[j+1:]
x_A1B2 = array_x2[j+1:]-array_x1[j]
y_A1B2 = array_y2[j+1:]-array_y1[j]
x_A2B1 = array_x2[j]-array_x1[j+1:]
y_A2B1 = array_y2[j]-array_y1[j+1:]
p1 = x_A1B1*y_A1A2 - y_A1B1*x_A1A2
p2 = x_A1B1*y_A1B2 - y_A1B1*x_A1B2
p3 = x_A2B2*y_A2B1 - y_A2B2*x_A2B1
p4 = x_A2B2*y_A2A1 - y_A2B2*x_A2A1
condicion_1=p1*p2
condicion_2=p3*p4
for k in xrange ((N+4)-j-1):
if condicion_1[k]<=0 and condicion_2[k]<=0:
M[j,k+j+1]=1
del condicion_1
del condicion_2
M[N,N+2]=0
M[N,N+3]=0
M[N+1,N+2]=0
M[N+1,N+3]=0
M[N+2,N]=0
M[N+2,N+1]=0
M[N+3,N]=0
M[N+3,N+1]=0
CD=np.array([])
POPOPO=[]
for g in xrange(N):
lala=0
r=False
while lala<=len(POPOPO)-1:
esta= g in POPOPO[lala]
if esta is True:
lala=len(POPOPO)
r=True
else:
lala=lala+1
if r is False:
L=np.array([g])
for s in xrange(N):
if M[g,s] != 0:
L=np.append(L,s)
x=0
while x<= N:
for l in xrange(N):
z= l in L
d=L[x]
if z is False and M[d,l] != 0:
L=np.append(L,l)
if x+1<len(L):
x+=1
else:
x=N+1.
q= len (L)
CD=np.append(CD, q)
POPOPO.append(L)
M_horizontal=M.copy()
M_horizontal[:,N+2] = np.zeros(N+4)
M_horizontal[:,N+3] = np.zeros(N+4)
M_horizontal[N+2] = np.zeros(N+4)
M_horizontal[N+3] = np.zeros(N+4)
L=np.array([N])
for s in xrange(N+4):
if M_horizontal[N,s] != 0:
L=np.append(L,s)
x=0
while x<= N+4:
for l in xrange(N+4):
z= l in L
d=L[x]
if z is False and M_horizontal[d,l] != 0:
L=np.append(L,l)
if x+1<len(L):
x+=1
else:
x=(N+4)+1.
LV1_in_L = N in L
LV2_in_L= (N+1) in L
if LV1_in_L is True and LV2_in_L is True:
perc_horiz=True
else:
perc_horiz=False
M_vertical=M.copy()
M_vertical[:,N] = np.zeros(N+4)
M_vertical[:,N+1] = np.zeros(N+4)
M_vertical[N] = np.zeros(N+4)
M_vertical[N+1] = np.zeros(N+4)
L=np.array([N+2])
for s in xrange(N+4):
if M_vertical[N+2,s] != 0:
L=np.append(L,s)
x=0
while x<= N+4:
for l in xrange(N+4):
z= l in L
d=L[x]
if z is False and M_vertical[d,l] != 0:
L=np.append(L,l)
if x+1<len(L):
x+=1
else:
x=(N+4)+1.
LH1_in_L = (N+2) in L
LH2_in_L= (N+3) in L
if LH1_in_L is True and LH2_in_L is True:
perc_ver = True
else:
perc_ver = False
if perc_ver is True or perc_horiz is True:
PERCOLACION=np.append(PERCOLACION,1)
perco=True
D = np.array([])
W = np.array([])
for c in xrange (int(min(CD)), int(max(CD)+1),1):
D=np.append(D,c)
frec = sum (CD == c)
W = np.append(W,frec)
if perco is True:
posicion=np.argmax(D)
D=np.delete(D,posicion)
W=np.delete(W,posicion)
if len(D) == 0 and len(W)==0:
S_medio_intuitivo_exp_u=0
S_medio_nuevo_exp_u = 0
std_dev_exp_u = 0
std_dev_nuevo_exp_u = 0
else:
S_medio_intuitivo_exp_u = np.average (D,weights=W)
peso_nuevo=D*W
S_medio_nuevo_exp_u = np.average (D,weights=peso_nuevo)
tipos=sum(W)
X=W*((D-S_medio_intuitivo_exp_u)**2)
S=sum(X)
std_dev_exp_u = np.sqrt(S/(tipos-1.))
tipos_nuevo=sum(peso_nuevo)
X_nuevo=peso_nuevo*((D-S_medio_nuevo_exp_u)**2)
S_nuevo=sum(X_nuevo)
std_dev_nuevo_exp_u = np.sqrt(S_nuevo/(tipos_nuevo-1.))
componente_longitudinal=Longitud*np.abs(np.cos(array_angle))
comp_y=np.append(comp_y, sum(componente_longitudinal)/N)
componente_transversal=Longitud*np.abs(np.sin(array_angle))
comp_x=np.append(comp_x, sum(componente_transversal)/N)
std_dev_size_medio_intuitivo=np.append(std_dev_size_medio_intuitivo, std_dev_exp_u)
std_dev_size_medio_nuevo=np.append(std_dev_size_medio_nuevo, std_dev_nuevo_exp_u)
size_medio_intuitivo=np.append(size_medio_intuitivo, S_medio_intuitivo_exp_u)
size_medio_nuevo=np.append(size_medio_nuevo, S_medio_nuevo_exp_u)
percolation_probability=sum(PERCOLACION)/numero_experimentos
prob_perc=np.append(prob_perc, percolation_probability)
S_int = np.append (S_int, sum(size_medio_intuitivo)/numero_experimentos)
S_medio=np.append (S_medio, sum(size_medio_nuevo)/numero_experimentos)
desviacion_standard = np.append (desviacion_standard, sum(std_dev_size_medio_intuitivo)/numero_experimentos)
desviacion_standard_nuevo=np.append (desviacion_standard_nuevo, sum(std_dev_size_medio_nuevo)/numero_experimentos)
tiempos=np.append(tiempos, time.clock()-empieza)
componente_y=np.append(componente_y, sum(comp_y)/numero_experimentos)
componente_x=np.append(componente_x, sum(comp_x)/numero_experimentos)
anisotropia_macroscopica_porcentual=100*(1-(componente_y/componente_x))
I tryed with gc and gc.collect() and 'del'command for deleting arrays after his use and nothing work!
What am I doing wrong? Why the memory becomes full while running (starts with 10% of RAM used and in 1-2hour is totally full used)?
Lets take an array M with size 300MB. When this is overwritten (for example, in each iteration), have we 300MB occupated in RAM memory or just 300MB? In the case that we have just 300MB, there should be no problem, so why have I this RAM issue? In the case of the RAM is acumulated, how can I do for free RAM memory occupated for the 'old' array?
Please help me, I'm totally stuck!
Thanks a lot!

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