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• ListView slow performance

  - by Mohamed Hemdan

  I've created a list of recipes using Listview/customcursoradapter. A custom layout includes a photo for the recipe , Now I've some problems with the performance of viewing and scrolling the Listview although it has only 10 records (Target is 150). sometimes i get this error java.lang.OutOfMemoryError: bitmap size exceeds VM budget , I've tried to implement the Async task but i failed to do it. Is there any way i can overcome this problem? Your help is highly appreciated !! Here is my GetView method public View getView(int position, View convertView, ViewGroup parent) { View row = super.getView(position, convertView, parent); Cursor cursbbn = getCursor(); if (row == null) { LayoutInflater inflater = (LayoutInflater) localContext.getSystemService(Context.LAYOUT_INFLATER_SERVICE); row = inflater.inflate(R.layout.listtype, null); } String Title = cursbbn.getString(2); String SandID=cursbbn.getString(1); String Readyin = cursbbn.getString(4); String Faovoites=cursbbn.getString(8); TextView titler=(TextView)row.findViewById(R.id.listmaintitle); TextView readyinr=(TextView)row.findViewById(R.id.listreadyin); int colorPos = position % colors.length; row.setBackgroundColor(colors[colorPos]); titler.setText(Title); readyinr.setText(Readyin); ImageView picture = (ImageView) row.findViewById(R.id.imageView1); Bitmap bitImg1 = BitmapFactory.decodeResource(localContext.getResources(), R.drawable.rec0001); Bitmap bitImg2 = BitmapFactory.decodeResource(localContext.getResources(), R.drawable.rec0002); Bitmap bitImg3 = BitmapFactory.decodeResource(localContext.getResources(), R.drawable.rec0003); Bitmap bitImg4 = BitmapFactory.decodeResource(localContext.getResources(), R.drawable.rec0004); Bitmap bitImg5 = BitmapFactory.decodeResource(localContext.getResources(), R.drawable.rec0005); Bitmap bitImg6 = BitmapFactory.decodeResource(localContext.getResources(), R.drawable.rec0006); Bitmap bitImg7 = BitmapFactory.decodeResource(localContext.getResources(), R.drawable.rec0007); Bitmap bitImg8 = BitmapFactory.decodeResource(localContext.getResources(), R.drawable.rec0008); Bitmap bitImg9 = BitmapFactory.decodeResource(localContext.getResources(), R.drawable.rec0009); Bitmap bitImg10 = BitmapFactory.decodeResource(localContext.getResources(), R.drawable.rec0010); if(SandID.contentEquals("0001")) picture.setImageBitmap(getRoundedCornerImage(bitImg1)); if(SandID.contentEquals("0002")) picture.setImageBitmap(getRoundedCornerImage(bitImg2)); if(SandID.contentEquals("0003")) picture.setImageBitmap(getRoundedCornerImage(bitImg3)); if(SandID.contentEquals("0004")) picture.setImageBitmap(getRoundedCornerImage(bitImg4)); if(SandID.contentEquals("0005")) picture.setImageBitmap(getRoundedCornerImage(bitImg5)); if(SandID.contentEquals("0006")) picture.setImageBitmap(getRoundedCornerImage(bitImg6)); if(SandID.contentEquals("0007")) picture.setImageBitmap(getRoundedCornerImage(bitImg7)); if(SandID.contentEquals("0008")) picture.setImageBitmap(getRoundedCornerImage(bitImg8)); if(SandID.contentEquals("0009")) picture.setImageBitmap(getRoundedCornerImage(bitImg9)); if(SandID.contentEquals("0010")) picture.setImageBitmap(getRoundedCornerImage(bitImg10)); return row; } And This is the error : 05-02 03:11:55.898: E/AndroidRuntime(376): FATAL EXCEPTION: main 05-02 03:11:55.898: E/AndroidRuntime(376): java.lang.OutOfMemoryError: bitmap size exceeds VM budget 05-02 03:11:55.898: E/AndroidRuntime(376): at android.graphics.BitmapFactory.nativeDecodeAsset(Native Method) 05-02 03:11:55.898: E/AndroidRuntime(376): at android.graphics.BitmapFactory.decodeStream(BitmapFactory.java:460) 05-02 03:11:55.898: E/AndroidRuntime(376): at android.graphics.BitmapFactory.decodeResourceStream(BitmapFactory.java:336) 05-02 03:11:55.898: E/AndroidRuntime(376): at android.graphics.BitmapFactory.decodeResource(BitmapFactory.java:359) 05-02 03:11:55.898: E/AndroidRuntime(376): at android.graphics.BitmapFactory.decodeResource(BitmapFactory.java:385) 05-02 03:11:55.898: E/AndroidRuntime(376): at master.chef.mediamaster.AlternateRowCursorAdapter.getView(AlternateRowCursorAdapter.java:83) 05-02 03:11:55.898: E/AndroidRuntime(376): at android.widget.AbsListView.obtainView(AbsListView.java:1409) 05-02 03:11:55.898: E/AndroidRuntime(376): at android.widget.ListView.makeAndAddView(ListView.java:1745) 05-02 03:11:55.898: E/AndroidRuntime(376): at android.widget.ListView.fillUp(ListView.java:700) 05-02 03:11:55.898: E/AndroidRuntime(376): at android.widget.ListView.fillGap(ListView.java:646) 05-02 03:11:55.898: E/AndroidRuntime(376): at android.widget.AbsListView.trackMotionScroll(AbsListView.java:3399) 05-02 03:11:55.898: E/AndroidRuntime(376): at android.widget.AbsListView.onTouchEvent(AbsListView.java:2233) 05-02 03:11:55.898: E/AndroidRuntime(376): at android.widget.ListView.onTouchEvent(ListView.java:3446) 05-02 03:11:55.898: E/AndroidRuntime(376): at android.view.View.dispatchTouchEvent(View.java:3885) 05-02 03:11:55.898: E/AndroidRuntime(376): at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:903) 05-02 03:11:55.898: E/AndroidRuntime(376): at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:942) 05-02 03:11:55.898: E/AndroidRuntime(376): at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:942) 05-02 03:11:55.898: E/AndroidRuntime(376): at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:942) 05-02 03:11:55.898: E/AndroidRuntime(376): at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:942) 05-02 03:11:55.898: E/AndroidRuntime(376): at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:942) 05-02 03:11:55.898: E/AndroidRuntime(376): at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:942) 05-02 03:11:55.898: E/AndroidRuntime(376): at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:942) 05-02 03:11:55.898: E/AndroidRuntime(376): at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:942) 05-02 03:11:55.898: E/AndroidRuntime(376): at com.android.internal.policy.impl.PhoneWindow$DecorView.superDispatchTouchEvent(PhoneWindow.java:1691) 05-02 03:11:55.898: E/AndroidRuntime(376): at com.android.internal.policy.impl.PhoneWindow.superDispatchTouchEvent(PhoneWindow.java:1125) 05-02 03:11:55.898: E/AndroidRuntime(376): at android.app.Activity.dispatchTouchEvent(Activity.java:2096) 05-02 03:11:55.898: E/AndroidRuntime(376): at com.android.internal.policy.impl.PhoneWindow$DecorView.dispatchTouchEvent(PhoneWindow.java:1675) 05-02 03:11:55.898: E/AndroidRuntime(376): at android.view.ViewRoot.deliverPointerEvent(ViewRoot.java:2194) 05-02 03:11:55.898: E/AndroidRuntime(376): at android.view.ViewRoot.handleMessage(ViewRoot.java:1878) 05-02 03:11:55.898: E/AndroidRuntime(376): at android.os.Handler.dispatchMessage(Handler.java:99) 05-02 03:11:55.898: E/AndroidRuntime(376): at android.os.Looper.loop(Looper.java:123) 05-02 03:11:55.898: E/AndroidRuntime(376): at android.app.ActivityThread.main(ActivityThread.java:3683) 05-02 03:11:55.898: E/AndroidRuntime(376): at java.lang.reflect.Method.invokeNative(Native Method) 05-02 03:11:55.898: E/AndroidRuntime(376): at java.lang.reflect.Method.invoke(Method.java:507) 05-02 03:11:55.898: E/AndroidRuntime(376): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839) 05-02 03:11:55.898: E/AndroidRuntime(376): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597) 05-02 03:11:55.898: E/AndroidRuntime(376): at dalvik.system.NativeStart.main(Native Method)

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• Optimizing python code performance when importing zipped csv to a mongo collection

  - by mark

  I need to import a zipped csv into a mongo collection, but there is a catch - every record contains a timestamp in Pacific Time, which must be converted to the local time corresponding to the (longitude,latitude) pair found in the same record. The code looks like so: def read_csv_zip(path, timezones): with ZipFile(path) as z, z.open(z.namelist()[0]) as input: csv_rows = csv.reader(input) header = csv_rows.next() check,converters = get_aux_stuff(header) for csv_row in csv_rows: if check(csv_row): row = { converter[0]:converter[1](value) for converter, value in zip(converters, csv_row) if allow_field(converter) } ts = row['ts'] lng, lat = row['loc'] found_tz_entry = timezones.find_one(SON({'loc': {'$within': {'$box': [[lng-tz_lookup_radius, lat-tz_lookup_radius],[lng+tz_lookup_radius, lat+tz_lookup_radius]]}}})) if found_tz_entry: tz_name = found_tz_entry['tz'] local_ts = ts.astimezone(timezone(tz_name)).replace(tzinfo=None) row['tz'] = tz_name else: local_ts = (ts.astimezone(utc) + timedelta(hours = int(lng/15))).replace(tzinfo = None) row['local_ts'] = local_ts yield row def insert_documents(collection, source, batch_size): while True: items = list(itertools.islice(source, batch_size)) if len(items) == 0: break; try: collection.insert(items) except: for item in items: try: collection.insert(item) except Exception as exc: print("Failed to insert record {0} - {1}".format(item['_id'], exc)) def main(zip_path): with Connection() as connection: data = connection.mydb.data timezones = connection.timezones.data insert_documents(data, read_csv_zip(zip_path, timezones), 1000) The code proceeds as follows: Every record read from the csv is checked and converted to a dictionary, where some fields may be skipped, some titles be renamed (from those appearing in the csv header), some values may be converted (to datetime, to integers, to floats. etc ...) For each record read from the csv, a lookup is made into the timezones collection to map the record location to the respective time zone. If the mapping is successful - that timezone is used to convert the record timestamp (pacific time) to the respective local timestamp. If no mapping is found - a rough approximation is calculated. The timezones collection is appropriately indexed, of course - calling explain() confirms it. The process is slow. Naturally, having to query the timezones collection for every record kills the performance. I am looking for advises on how to improve it. Thanks. EDIT The timezones collection contains 8176040 records, each containing four values: > db.data.findOne() { "_id" : 3038814, "loc" : [ 1.48333, 42.5 ], "tz" : "Europe/Andorra" } EDIT2 OK, I have compiled a release build of http://toblerity.github.com/rtree/ and configured the rtree package. Then I have created an rtree dat/idx pair of files corresponding to my timezones collection. So, instead of calling collection.find_one I call index.intersection. Surprisingly, not only there is no improvement, but it works even more slowly now! May be rtree could be fine tuned to load the entire dat/idx pair into RAM (704M), but I do not know how to do it. Until then, it is not an alternative. In general, I think the solution should involve parallelization of the task. EDIT3 Profile output when using collection.find_one: >>> p.sort_stats('cumulative').print_stats(10) Tue Apr 10 14:28:39 2012 ImportDataIntoMongo.profile 64549590 function calls (64549180 primitive calls) in 1231.257 seconds Ordered by: cumulative time List reduced from 730 to 10 due to restriction <10> ncalls tottime percall cumtime percall filename:lineno(function) 1 0.012 0.012 1231.257 1231.257 ImportDataIntoMongo.py:1(<module>) 1 0.001 0.001 1230.959 1230.959 ImportDataIntoMongo.py:187(main) 1 853.558 853.558 853.558 853.558 {raw_input} 1 0.598 0.598 370.510 370.510 ImportDataIntoMongo.py:165(insert_documents) 343407 9.965 0.000 359.034 0.001 ImportDataIntoMongo.py:137(read_csv_zip) 343408 2.927 0.000 287.035 0.001 c:\python27\lib\site-packages\pymongo\collection.py:489(find_one) 343408 1.842 0.000 274.803 0.001 c:\python27\lib\site-packages\pymongo\cursor.py:699(next) 343408 2.542 0.000 271.212 0.001 c:\python27\lib\site-packages\pymongo\cursor.py:644(_refresh) 343408 4.512 0.000 253.673 0.001 c:\python27\lib\site-packages\pymongo\cursor.py:605(__send_message) 343408 0.971 0.000 242.078 0.001 c:\python27\lib\site-packages\pymongo\connection.py:871(_send_message_with_response) Profile output when using index.intersection: >>> p.sort_stats('cumulative').print_stats(10) Wed Apr 11 16:21:31 2012 ImportDataIntoMongo.profile 41542960 function calls (41542536 primitive calls) in 2889.164 seconds Ordered by: cumulative time List reduced from 778 to 10 due to restriction <10> ncalls tottime percall cumtime percall filename:lineno(function) 1 0.028 0.028 2889.164 2889.164 ImportDataIntoMongo.py:1(<module>) 1 0.017 0.017 2888.679 2888.679 ImportDataIntoMongo.py:202(main) 1 2365.526 2365.526 2365.526 2365.526 {raw_input} 1 0.766 0.766 502.817 502.817 ImportDataIntoMongo.py:180(insert_documents) 343407 9.147 0.000 491.433 0.001 ImportDataIntoMongo.py:152(read_csv_zip) 343406 0.571 0.000 391.394 0.001 c:\python27\lib\site-packages\rtree-0.7.0-py2.7.egg\rtree\index.py:384(intersection) 343406 379.957 0.001 390.824 0.001 c:\python27\lib\site-packages\rtree-0.7.0-py2.7.egg\rtree\index.py:435(_intersection_obj) 686513 22.616 0.000 38.705 0.000 c:\python27\lib\site-packages\rtree-0.7.0-py2.7.egg\rtree\index.py:451(_get_objects) 343406 6.134 0.000 33.326 0.000 ImportDataIntoMongo.py:162(<dictcomp>) 346 0.396 0.001 30.665 0.089 c:\python27\lib\site-packages\pymongo\collection.py:240(insert) EDIT4 I have parallelized the code, but the results are still not very encouraging. I am convinced it could be done better. See my own answer to this question for details.

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• How optimize code with introspection + heavy alloc on iPhone

  - by mamcx

  I have a problem. I try to display a UITable that could have 2000-20000 records (typicall numbers.) I have a SQLite database similar to the Apple contacts application. I do all the tricks I know to get a smoth scroll, but I have a problem. I load the data in 50 recods blocks. Then, when the user scroll, request next 50 until finish the list. However, load that 50 records cause a notable "pause" in loading and scrolling. Everything else works fine. I cache the data, have opaque cells, draw it by code, etc... I swap the code loading the same data in dicts and have a performance boost but wonder if I could keep my object oriented aproach and improve the actual code. This is the code I think have the performance problem: -(NSArray *) loadAndFill: (NSString *)sql theClass: (Class)cls { [self openDb]; NSMutableArray *list = [NSMutableArray array]; NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init]; DbObject *ds; Class myClass = NSClassFromString([DbObject getTableName:cls]); FMResultSet *rs = [self load:sql]; while ([rs next]) { ds = [[myClass alloc] init]; NSDictionary *props = [ds properties]; NSString *fieldType = nil; id fieldValue; for (NSString *fieldName in [props allKeys]) { fieldType = [props objectForKey: fieldName]; fieldValue = [self ValueForField:rs Name:fieldName Type:fieldType]; [ds setValue:fieldValue forKey:fieldName]; } [list addObject :ds]; [ds release]; } [rs close]; [pool drain]; return list; } And I think the main culprit is: -(id) ValueForField: (FMResultSet *)rs Name:(NSString *)fieldName Type:(NSString *)fieldType { id fieldValue = nil; if ([fieldType isEqualToString:@"i"] || // int [fieldType isEqualToString:@"I"] || // unsigned int [fieldType isEqualToString:@"s"] || // short [fieldType isEqualToString:@"S"] || // unsigned short [fieldType isEqualToString:@"f"] || // float [fieldType isEqualToString:@"d"] ) // double { fieldValue = [NSNumber numberWithInt: [rs longForColumn:fieldName]]; } else if ([fieldType isEqualToString:@"B"]) // bool or _Bool { fieldValue = [NSNumber numberWithBool: [rs boolForColumn:fieldName]]; } else if ([fieldType isEqualToString:@"l"] || // long [fieldType isEqualToString:@"L"] || // usigned long [fieldType isEqualToString:@"q"] || // long long [fieldType isEqualToString:@"Q"] ) // unsigned long long { fieldValue = [NSNumber numberWithLong: [rs longForColumn:fieldName]]; } else if ([fieldType isEqualToString:@"c"] || // char [fieldType isEqualToString:@"C"] ) // unsigned char { fieldValue = [rs stringForColumn:fieldName]; //Is really a boolean? if ([fieldValue isEqualToString:@"0"] || [fieldValue isEqualToString:@"1"]) { fieldValue = [NSNumber numberWithInt: [fieldValue intValue]]; } } else if ([fieldType hasPrefix:@"@"] ) // Object { NSString *className = [fieldType substringWithRange:NSMakeRange(2, [fieldType length]-3)]; if ([className isEqualToString:@"NSString"]) { fieldValue = [rs stringForColumn:fieldName]; } else if ([className isEqualToString:@"NSDate"]) { NSDateFormatter* dateFormatter = [[NSDateFormatter alloc] init]; [dateFormatter setDateFormat:@"yyyy-MM-dd'T'HH:mm:ss"]; NSString *theDate = [rs stringForColumn:fieldName]; if (theDate) { fieldValue = [dateFormatter dateFromString: theDate]; } else { fieldValue = nil; } [dateFormatter release]; } else if ([className isEqualToString:@"NSInteger"]) { fieldValue = [NSNumber numberWithInt: [rs intForColumn :fieldName]]; } else if ([className isEqualToString:@"NSDecimalNumber"]) { fieldValue = [rs stringForColumn :fieldName]; if (fieldValue) { fieldValue = [NSDecimalNumber decimalNumberWithString:[rs stringForColumn :fieldName]]; } } else if ([className isEqualToString:@"NSNumber"]) { fieldValue = [NSNumber numberWithDouble: [rs doubleForColumn:fieldName]]; } else { //Is a relationship one-to-one? if (![fieldType hasPrefix:@"NS"]) { id rel = class_createInstance(NSClassFromString(className), sizeof(unsigned)); Class theClass = [rel class]; if ([rel isKindOfClass:[DbObject class]]) { fieldValue = [rel init]; //Load the record... NSInteger Id = [rs intForColumn:[theClass relationName]]; if (Id>0) { [fieldValue release]; Db *db = [Db currentDb]; fieldValue = [db loadById: theClass theId:Id]; } } } else { NSString *error = [NSString stringWithFormat:@"Err Can't get value for field %@ of type %@", fieldName, fieldType]; NSLog(error); NSException *e = [NSException exceptionWithName:@"DBError" reason:error userInfo:nil]; @throw e; } } } return fieldValue; }

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• Using UUIDs for cheap equals() and hashCode()

  - by Tom McIntyre

  I have an immutable class, TokenList, which consists of a list of Token objects, which are also immutable: @Immutable public final class TokenList { private final List<Token> tokens; public TokenList(List<Token> tokens) { this.tokens = Collections.unmodifiableList(new ArrayList(tokens)); } public List<Token> getTokens() { return tokens; } } I do several operations on these TokenLists that take multiple TokenLists as inputs and return a single TokenList as the output. There can be arbitrarily many TokenLists going in, and each can have arbitrarily many Tokens. These operations are expensive, and there is a good chance that the same operation (ie the same inputs) will be performed multiple times, so I would like to cache the outputs. However, performance is critical, and I am worried about the expense of performing hashCode() and equals() on these objects that may contain arbitrarily many elements (as they are immutable then hashCode could be cached, but equals will still be expensive). This led me to wondering whether I could use a UUID to provide equals() and hashCode() simply and cheaply by making the following updates to TokenList: @Immutable public final class TokenList { private final List<Token> tokens; private final UUID uuid; public TokenList(List<Token> tokens) { this.tokens = Collections.unmodifiableList(new ArrayList(tokens)); this.uuid = UUID.randomUUID(); } public List<Token> getTokens() { return tokens; } public UUID getUuid() { return uuid; } } And something like this to act as a cache key: @Immutable public final class TopicListCacheKey { private final UUID[] uuids; public TopicListCacheKey(TopicList... topicLists) { uuids = new UUID[topicLists.length]; for (int i = 0; i < uuids.length; i++) { uuids[i] = topicLists[i].getUuid(); } } @Override public int hashCode() { return Arrays.hashCode(uuids); } @Override public boolean equals(Object other) { if (other == this) return true; if (other instanceof TopicListCacheKey) return Arrays.equals(uuids, ((TopicListCacheKey) other).uuids); return false; } } I figure that there are 2^128 different UUIDs and I will probably have at most around 1,000,000 TokenList objects active in the application at any time. Given this, and the fact that the UUIDs are used combinatorially in cache keys, it seems that the chances of this producing the wrong result are vanishingly small. Nevertheless, I feel uneasy about going ahead with it as it just feels 'dirty'. Are there any reasons I should not use this system? Will the performance costs of the SecureRandom used by UUID.randomUUID() outweigh the gains (especially since I expect multiple threads to be doing this at the same time)? Are collisions going to be more likely than I think? Basically, is there anything wrong with doing it this way?? Thanks.

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• Make c# matrix code faster

  - by Wam

  Hi all, Working on some matrix code, I'm concerned of performance issues. here's how it works : I've a IMatrix abstract class (with all matrices operations etc), implemented by a ColumnMatrix class. abstract class IMatrix { public int Rows {get;set;} public int Columns {get;set;} public abstract float At(int row, int column); } class ColumnMatrix : IMatrix { private data[]; public override float At(int row, int column) { return data[row + columns * this.Rows]; } } This class is used a lot across my application, but I'm concerned with performance issues. Testing only read for a 2000000x15 matrix against a jagged array of the same size, I get 1359ms for array access agains 9234ms for matrix access : public void TestAccess() { int iterations = 10; int rows = 2000000; int columns = 15; ColumnMatrix matrix = new ColumnMatrix(rows, columns); for (int i = 0; i < rows; i++) for (int j = 0; j < columns; j++) matrix[i, j] = i + j; float[][] equivalentArray = matrix.ToRowsArray(); TimeSpan totalMatrix = new TimeSpan(0); TimeSpan totalArray = new TimeSpan(0); float total = 0f; for (int iteration = 0; iteration < iterations; iteration++) { total = 0f; DateTime start = DateTime.Now; for (int i = 0; i < rows; i++) for (int j = 0; j < columns; j++) total = matrix.At(i, j); totalMatrix += (DateTime.Now - start); total += 1f; //Ensure total is read at least once. total = total > 0 ? 0f : 0f; start = DateTime.Now; for (int i = 0; i < rows; i++) for (int j = 0; j < columns; j++) total = equivalentArray[i][j]; totalArray += (DateTime.Now - start); } if (total < 0f) logger.Info("Nothing here, just make sure we read total at least once."); logger.InfoFormat("Average time for a {0}x{1} access, matrix : {2}ms", rows, columns, totalMatrix.TotalMilliseconds); logger.InfoFormat("Average time for a {0}x{1} access, array : {2}ms", rows, columns, totalArray.TotalMilliseconds); Assert.IsTrue(true); } So my question : how can I make this thing faster ? Is there any way I can make my ColumnMatrix.At faster ? Cheers !

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• C++ Optimize if/else condition

  - by Heye

  I have a single line of code, that consumes 25% - 30% of the runtime of my application. It is a less-than comparator for an std::set (the set is implemented with a Red-Black-Tree). It is called about 180 Million times within 52 seconds. struct Entry { const float _cost; const long _id; // some other vars Entry(float cost, float id) : _cost(cost), _id(id) { } }; template<class T> struct lt_entry: public binary_function <T, T, bool> { bool operator()(const T &l, const T &r) const { // Most readable shape if(l._cost != r._cost) { return r._cost < l._cost; } else { return l._id < r._id; } } }; The entries should be sorted by cost and if the cost is the same by their id. I have many insertions for each extraction of the minimum. I thought about using Fibonacci-Heaps, but I have been told that they are theoretically nice, but suffer from high constants and are pretty complicated to implement. And since insert is in O(log(n)) the runtime increase is nearly constant with large n. So I think its okay to stick to the set. To improve performance I tried to express it in different shapes: return l._cost < r._cost || r._cost > l._cost || l._id < r._id; return l._cost < r._cost || (l._cost == r._cost && l._id < r._id); Even this: typedef union { float _f; int _i; } flint; //... flint diff; diff._f = (l._cost - r._cost); return (diff._i && diff._i >> 31) || l._id < r._id; But the compiler seems to be smart enough already, because I haven't been able to improve the runtime. I also thought about SSE but this problem is really not very applicable for SSE... The assembly looks somewhat like this: movss (%rbx),%xmm1 mov $0x1,%r8d movss 0x20(%rdx),%xmm0 ucomiss %xmm1,%xmm0 ja 0x410600 <_ZNSt8_Rb_tree[..]+96> ucomiss %xmm0,%xmm1 jp 0x4105fd <_ZNSt8_Rb_[..]_+93> jne 0x4105fd <_ZNSt8_Rb_[..]_+93> mov 0x28(%rdx),%rax cmp %rax,0x8(%rbx) jb 0x410600 <_ZNSt8_Rb_[..]_+96> xor %r8d,%r8d I have a very tiny bit experience with assembly language, but not really much. I thought it would be the best (only?) point to squeeze out some performance, but is it really worth the effort? Can you see any shortcuts that could save some cycles? The platform the code will run on is an ubuntu 12 with gcc 4.6 (-stl=c++0x) on a many-core intel machine. Only libraries available are boost, openmp and tbb. I am really stuck on this one, it seems so simple, but takes that much time. I have been crunching my head since days thinking how I could improve this line... Can you give me a suggestion how to improve this part, or is it already at its best?

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• What's the fastest lookup algorithm for a pair data structure (i.e, a map)?

  - by truncheon

  In the following example a std::map structure is filled with 26 values from A - Z (for key) and 0 – 26 for value. The time taken (on my system) to lookup the last entry (10000000 times) is roughly 250 ms for the vector, and 125 ms for the map. (I compiled using release mode, with O3 option turned on for g++ 4.4) But if for some odd reason I wanted better performance than the std::map, what data structures and functions would I need to consider using? I apologize if the answer seems obvious to you, but I haven't had much experience in the performance critical aspects of C++ programming. UPDATE: This example is rather trivial and hides the true complexity of what I'm trying to achieve. My real world project is a simple scripting language that uses a parser, data tree, and interpreter (instead of a VM stack system). I need to use some kind of data structure (perhaps map) to store the variables names created by script programmers. These are likely to be pretty randomly named, so I need a lookup method that can quickly find a particular key within a (probably) fairly large list of names. #include <ctime> #include <map> #include <vector> #include <iostream> struct mystruct { char key; int value; mystruct(char k = 0, int v = 0) : key(k), value(v) { } }; int find(const std::vector<mystruct>& ref, char key) { for (std::vector<mystruct>::const_iterator i = ref.begin(); i != ref.end(); ++i) if (i->key == key) return i->value; return -1; } int main() { std::map<char, int> mymap; std::vector<mystruct> myvec; for (int i = 'a'; i < 'a' + 26; ++i) { mymap[i] = i - 'a'; myvec.push_back(mystruct(i, i - 'a')); } int pre = clock(); for (int i = 0; i < 10000000; ++i) { find(myvec, 'z'); } std::cout << "linear scan: milli " << clock() - pre << "\n"; pre = clock(); for (int i = 0; i < 10000000; ++i) { mymap['z']; } std::cout << "map scan: milli " << clock() - pre << "\n"; return 0; }

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• Performance Testing &ndash; Quick Reference Guide &ndash; Released up on CodePlex

  - by Shawn Cicoria

  Why performance test at all right?  Well, physics still plays a role in what we do.  Why not take a better look at your application – need help, well, the Rangers team just released the following to help: The following has both VS2008 & VS2010 content: http://vstt2008qrg.codeplex.com/ Visual Studio Performance Testing Quick Reference Guide (Version 2.0) The final released copy is here and ready for full time use. Please enjoy and post feedback on the discussion board. This document is a collection of items from public blog sites, Microsoft® internal discussion aliases (sanitized) and experiences from various Test Consultants in the Microsoft Services Labs. The idea is to provide quick reference points around various aspects of Microsoft Visual Studio® performance testing features that may not be covered in core documentation, or may not be easily understood. The different types of information cover: How does this feature work under the covers? How can I implement a workaround for this missing feature? This is a known bug and here is a fix or workaround. How do I troubleshoot issues I am having

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• xsd validation againts xsd generated class level validation

  - by Miral

  In my project I have very big XSD file which i use to validate some XML request and response to a 3rd party. For the above scenario I can have 2 approaches 1) Create XML and then validate against give XSD 2) Create classes from XSD with the help of XSD gen tool, add xtra bit of attirbutes and use them for validation. Validation in the second way will work somewhat in this manner, a) convert xml request/response into object with XML Serialization b) validate the object with custom attributes set on each property, i.e. Pass the object to a method which will validate the object by iterating through properties and its custom attributes set on the each property, and this will return a boolean value if the object validates and that determines whether the xml request is valid or not? Now the concern which approach is good in terms of performance and anything else???

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• Using Lite Version of Entity in nHibernate Relations?

  - by Amitabh

  Is it a good idea to create a lighter version of an Entity in some cases just for performance reason pointing to same table but with fewer columns mapped. E.g If I have a Contact Table which has 50 Columns and in few of the related entities I might be interested in FirstName and LastName property is it a good idea to create a lightweight version of Contact table. E.g. public class ContactLite { public int Id {get; set;} public string FirstName {get; set;} public string LastName {get; set;} } Also is it possible to map multiple classes to same table?

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• C# winforms Picturebox, backgroundimage zoomed at the top?

  - by Oskar Kjellin

  I have a picturebox where I set change the BackgroundImage frequently. I have a the BackgroundImageLayout set to Zoom. The problem is that when an image does not have the same scale as the picturebox, the picture is drawn in the middle. That is, the top and the bottom padding of the picturebox is always the same. I would like for the BackgroundImage to always be aligned at the top. What is the easiest and most performance efficient way of doing this? I can add that I download the images from the internet. If you think that the best way to deal with this is to resize them at that point I can do that :)

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• How to throttle clients in a REST API

  - by Jacques René Mesrine

  I want to limit clients to an upper limit of number of calls to my REST APIs. What should I return to inform clients that they've been throttled ? Amazon S3 is returning HTTP 503 with an error code SlowDown to inform clients. What do you advise ?

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• Database design for very large amount of data

  - by Hossein

  Hi, I am working on a project, involving large amount of data from the delicious website.The data available is at files are "Date,UserId,Url,Tags" (for each bookmark). I normalized my database to a 3NF, and because of the nature of the queries that we wanted to use In combination I came down to 6 tables....The design looks fine, however, now a large amount of data is in the database, most of the queries needs to "join" at least 2 tables together to get the answer, sometimes 3 or 4. At first, we didn't have any performance issues, because for testing matters we haven't had added too much data in the database. No that we have a lot of data, simply joining extremely large tables does take a lot of time and for our project which has to be real-time is a disaster.I was wondering how big companies solve these issues.Looks like normalizing tables just adds complexity, but how does the big company handle large amounts of data in their databases, don't they do the normalization? thanks

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• dynamic insert php mysql and preformance

  - by Ross

  I have a folder/array of images, it may be 1, maximum of 12. What I need to do is dynamically add them so the images are added to an images table. At the moment I have $directory = "portfolio_images/$id/Thumbs/"; $images = glob("" . $directory . "*.jpg"); for ( $i= 0; $i <= count($images); $i += 1) { mysql_query("INSERT INTO project_images (image_name, project_id)VALUES ('$images[0]', '$id')") or die(mysql_error()); } this is fine but it does not feel right, how is this for performance? Is there a better way? The maximum number of images is only ever going to be 12. Thanks, Ross

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• How to optimize simple linked server select query?

  - by tomaszs

  Hello, I have a table called Table with columns: ID (int, primary key, clustered, unique index) TEXT (varchar 15) on a MSSQL linked server called LS. Linked server is on the same server computer. And: When I call: SELECT ID, TEXT FROM OPENQUERY(LS, 'SELECT ID, TEXT FROM Table') It takes 400 ms. When I call: SELECT ID, TEXT FROM LS.dbo.Table It takes 200 ms And when I call the query directly while being at LS server: SELECT ID, TEXT FROM dbo.Table It takes 100 ms. In many places i've read that OPENQUERY is faster, but in this simple case it does not seem to work. What can I do to make this query faster when I call it from another server, not LS directly?

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• JDBC resultset close

  - by KM

  I am doing profiling of my Java application and found some interesting statistics for a jdbc PreparedStatement call: Given below is the environment details: Database: Sybase SQL Anywhere 10.0.1 Driver: com.sybase.jdbc3.jdbc.SybDriver connection pool: c3p0 JRE: 1.6.0_05 The code in question is given below: try { ps = conn.prepareStatement(sql); ps.setDouble(...); rs = ps.executeQuery(); ...... return xyz; } finally { try { if (rs != null) rs.close(); if (ps != null) ps.close(); } catch (SQLException sqlEx) { } } From JProfiler stats, I find that this particular resultspace.close() statement alone takes a large amount of time. It varies from 25 ms to 320s while for other code blocks which are of identical in nature, i find that this takes close to 20 microseconds. Just to be sure, I ran this performance test multiple times and confirmed this data. I am puzzled by this behaviour - Thoughts?

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• VS 2010 very slow

  - by kaze

  I have just upgraded to VS 2010, and I have performance problems which I did not have before (in VS 2008). The most annoying thing is that it freezes while I work in the text editor. Sometimes when it freezes I see that it is saving auto recovery information, but not always. Almost anything I do gives an unacceptable long delay, like saving, starting to debug, ending debug session, switching between design and code view, and doing WinForms designing. I have some parts of my home directory on a mapped network drive. I suspect that that might be a part of the problem. Is it possible to configure VS 2010 to use exclusively local disk for its "internal" work perhaps? Any hints would be appreciated! Has anyone else experienced these kinds of problems?

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• Java - When to use Iterators?

  - by Walter White

  Hi all, I am trying to better understand when I should and should not use Iterators. To me, whenever I have a potentially large amount of data to iterate through, I write an Iterator for it. If it also lends itself to the Iterator interface, then it seems like a win. I was reading a little bit that there is a lot of overhead with using an Iterator. A good example of where I used an Iterator was to iterate through a bunch of SQL scripts to execute one query at a time, reading it in, then executing it. Is there another performance trade off I should be aware of? Before I used iterators, I would read the entire String of SQL commands to execute into an ArrayList, and the iterate through that. If the import is rather large (like for geolocation data, then the server tends to get bogged down). Walter

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• Slow Execution of an ASP.NET Web Page

  - by Sweta Jha

  I have a web page which brings 13K+ records in 20 seconds. There is a menu on the page, clicking on which navigates me to another page which is very lightweight. Displaying the data (13K+) took only 20 seconds whereas navigating from that page took much longer, more than 2 mins. Can you tell me why is the latter taking so much of time. I've stopped the page_load code execution on click of the menu. I've disabled the viewstate for that page as well.

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• Actual table Vs. Div table

  - by omfgroflmao

  This <table> <tr> <td>Hello</td> <td>World</td> </tr> </table> Can be done with this: <div> <div style="display: table-row;"> <div style="display: table-cell;">Hello</div> <div style="display: table-cell;">World</div> </div> </div> Now, is there any difference between these two in terms of performance and/or render speed or they're just the same?

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• Database Network Latency

  - by Karl

  Hi All, I am currently working on an n-tier system and battling some database performance issues. One area we have been investigating is the latency between the database server and the application server. In our test environment the average ping times between the two boxes is in the region of 0.2ms however on the clients site its more in the region of 8.2 ms. Is that somthing we should be worried about? For your average system what do you guys consider a resonable latency and how would you go about testing/measuring the latency? Karl

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• Should i really use integer primary IDs?

  - by arthurprs

  For example, i always generate an auto-increment field for the users table, but i also specifies an UNIQUE index on their usernames. There is situations that i first need to get the userId for a given username and then execute the desired query. Or use a JOIN in the desired query. It's 2 trips to the database or a JOIN vs. a varchar index The above is just an example There is a real performance benefit on INT over small VARCHAR indexes? Thanks in advance!

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• How to utilize my computation resources.

  - by carter-boater

  Hi all, I wrote a program to solve a complicated problem. This program is just a c# console application and doesn't do console.write until the computation part is finished, so output won't affect the performance. The program is like this: static void Main(string[] args) { Thread WorkerThread = new Thread(new ThreadStart(Run), StackSize); WorkerThread.Priority = ThreadPriority.Highest; WorkerThread.Start(); Console.WriteLine("Worker thread is runing..."); WorkerThread.Join(); } Now it takes 3 minute to run, when I open my task manager, I see it only take 12% of the cpu time. I actually have a i7 intel cpu with 6G three channel DDR3 memory. I am wondering how I can improve the utilization of my hardware. Thanks a lot

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• Why is Oracle using a skip scan for this query?

  - by Jason Baker

  Here's the tkprof output for a query that's running extremely slowly (WARNING: it's long :-) ): SELECT mbr_comment_idn, mbr_crt_dt, mbr_data_source, mbr_dol_bl_rmo_ind, mbr_dxcg_ctl_member, mbr_employment_start_dt, mbr_employment_term_dt, mbr_entity_active, mbr_ethnicity_idn, mbr_general_health_status_code, mbr_hand_dominant_code, mbr_hgt_feet, mbr_hgt_inches, mbr_highest_edu_level, mbr_insd_addr_idn, mbr_insd_alt_id, mbr_insd_name, mbr_insd_ssn_tin, mbr_is_smoker, mbr_is_vip, mbr_lmbr_first_name, mbr_lmbr_last_name, mbr_marital_status_cd, mbr_mbr_birth_dt, mbr_mbr_death_dt, mbr_mbr_expired, mbr_mbr_first_name, mbr_mbr_gender_cd, mbr_mbr_idn, mbr_mbr_ins_type, mbr_mbr_isreadonly, mbr_mbr_last_name, mbr_mbr_middle_name, mbr_mbr_name, mbr_mbr_status_idn, mbr_mpi_id, mbr_preferred_am_pm, mbr_preferred_time, mbr_prv_innetwork, mbr_rep_addr_idn, mbr_rep_name, mbr_rp_mbr_id, mbr_same_mbr_ins, mbr_special_needs_cd, mbr_timezone, mbr_upd_dt, mbr_user_idn, mbr_wgt, mbr_work_status_idn FROM (SELECT /*+ FIRST_ROWS(1) */ mbr_comment_idn, mbr_crt_dt, mbr_data_source, mbr_dol_bl_rmo_ind, mbr_dxcg_ctl_member, mbr_employment_start_dt, mbr_employment_term_dt, mbr_entity_active, mbr_ethnicity_idn, mbr_general_health_status_code, mbr_hand_dominant_code, mbr_hgt_feet, mbr_hgt_inches, mbr_highest_edu_level, mbr_insd_addr_idn, mbr_insd_alt_id, mbr_insd_name, mbr_insd_ssn_tin, mbr_is_smoker, mbr_is_vip, mbr_lmbr_first_name, mbr_lmbr_last_name, mbr_marital_status_cd, mbr_mbr_birth_dt, mbr_mbr_death_dt, mbr_mbr_expired, mbr_mbr_first_name, mbr_mbr_gender_cd, mbr_mbr_idn, mbr_mbr_ins_type, mbr_mbr_isreadonly, mbr_mbr_last_name, mbr_mbr_middle_name, mbr_mbr_name, mbr_mbr_status_idn, mbr_mpi_id, mbr_preferred_am_pm, mbr_preferred_time, mbr_prv_innetwork, mbr_rep_addr_idn, mbr_rep_name, mbr_rp_mbr_id, mbr_same_mbr_ins, mbr_special_needs_cd, mbr_timezone, mbr_upd_dt, mbr_user_idn, mbr_wgt, mbr_work_status_idn, ROWNUM AS ora_rn FROM (SELECT mbr.comment_idn AS mbr_comment_idn, mbr.crt_dt AS mbr_crt_dt, mbr.data_source AS mbr_data_source, mbr.dol_bl_rmo_ind AS mbr_dol_bl_rmo_ind, mbr.dxcg_ctl_member AS mbr_dxcg_ctl_member, mbr.employment_start_dt AS mbr_employment_start_dt, mbr.employment_term_dt AS mbr_employment_term_dt, mbr.entity_active AS mbr_entity_active, mbr.ethnicity_idn AS mbr_ethnicity_idn, mbr.general_health_status_code AS mbr_general_health_status_code, mbr.hand_dominant_code AS mbr_hand_dominant_code, mbr.hgt_feet AS mbr_hgt_feet, mbr.hgt_inches AS mbr_hgt_inches, mbr.highest_edu_level AS mbr_highest_edu_level, mbr.insd_addr_idn AS mbr_insd_addr_idn, mbr.insd_alt_id AS mbr_insd_alt_id, mbr.insd_name AS mbr_insd_name, mbr.insd_ssn_tin AS mbr_insd_ssn_tin, mbr.is_smoker AS mbr_is_smoker, mbr.is_vip AS mbr_is_vip, mbr.lmbr_first_name AS mbr_lmbr_first_name, mbr.lmbr_last_name AS mbr_lmbr_last_name, mbr.marital_status_cd AS mbr_marital_status_cd, mbr.mbr_birth_dt AS mbr_mbr_birth_dt, mbr.mbr_death_dt AS mbr_mbr_death_dt, mbr.mbr_expired AS mbr_mbr_expired, mbr.mbr_first_name AS mbr_mbr_first_name, mbr.mbr_gender_cd AS mbr_mbr_gender_cd, mbr.mbr_idn AS mbr_mbr_idn, mbr.mbr_ins_type AS mbr_mbr_ins_type, mbr.mbr_isreadonly AS mbr_mbr_isreadonly, mbr.mbr_last_name AS mbr_mbr_last_name, mbr.mbr_middle_name AS mbr_mbr_middle_name, mbr.mbr_name AS mbr_mbr_name, mbr.mbr_status_idn AS mbr_mbr_status_idn, mbr.mpi_id AS mbr_mpi_id, mbr.preferred_am_pm AS mbr_preferred_am_pm, mbr.preferred_time AS mbr_preferred_time, mbr.prv_innetwork AS mbr_prv_innetwork, mbr.rep_addr_idn AS mbr_rep_addr_idn, mbr.rep_name AS mbr_rep_name, mbr.rp_mbr_id AS mbr_rp_mbr_id, mbr.same_mbr_ins AS mbr_same_mbr_ins, mbr.special_needs_cd AS mbr_special_needs_cd, mbr.timezone AS mbr_timezone, mbr.upd_dt AS mbr_upd_dt, mbr.user_idn AS mbr_user_idn, mbr.wgt AS mbr_wgt, mbr.work_status_idn AS mbr_work_status_idn FROM mbr JOIN mbr_identfn ON mbr.mbr_idn = mbr_identfn.mbr_idn WHERE mbr_identfn.mbr_idn = mbr.mbr_idn AND mbr_identfn.identfd_type = :identfd_type_1 AND mbr_identfn.identfd_number = :identfd_number_1 AND mbr_identfn.entity_active = :entity_active_1) WHERE ROWNUM <= :ROWNUM_1) WHERE ora_rn > :ora_rn_1 call count cpu elapsed disk query current rows ------- ------ -------- ---------- ---------- ---------- ---------- ---------- Parse 9936 0.46 0.49 0 0 0 0 Execute 9936 0.60 0.59 0 0 0 0 Fetch 9936 329.87 404.00 0 136966922 0 0 ------- ------ -------- ---------- ---------- ---------- ---------- ---------- total 29808 330.94 405.09 0 136966922 0 0 Misses in library cache during parse: 0 Optimizer mode: FIRST_ROWS Parsing user id: 36 (JIVA_DEV) Rows Row Source Operation ------- --------------------------------------------------- 0 VIEW (cr=102 pr=0 pw=0 time=2180 us) 0 COUNT STOPKEY (cr=102 pr=0 pw=0 time=2163 us) 0 NESTED LOOPS (cr=102 pr=0 pw=0 time=2152 us) 0 INDEX SKIP SCAN IDX_MBR_IDENTFN (cr=102 pr=0 pw=0 time=2140 us)(object id 341053) 0 TABLE ACCESS BY INDEX ROWID MBR (cr=0 pr=0 pw=0 time=0 us) 0 INDEX UNIQUE SCAN PK_CLAIMANT (cr=0 pr=0 pw=0 time=0 us)(object id 334044) Rows Execution Plan ------- --------------------------------------------------- 0 SELECT STATEMENT MODE: HINT: FIRST_ROWS 0 VIEW 0 COUNT (STOPKEY) 0 NESTED LOOPS 0 INDEX MODE: ANALYZED (SKIP SCAN) OF 'IDX_MBR_IDENTFN' (INDEX (UNIQUE)) 0 TABLE ACCESS MODE: ANALYZED (BY INDEX ROWID) OF 'MBR' (TABLE) 0 INDEX MODE: ANALYZED (UNIQUE SCAN) OF 'PK_CLAIMANT' (INDEX (UNIQUE)) ******************************************************************************** Based on my reading of Oracle's documentation of skip scans, a skip scan is most useful when the first column of an index has a low number of unique values. The thing is that the first index of this column is a unique primary key. So am I correct in assuming that a skip scan is the wrong thing to do here? Also, what kind of scan should it be doing? Should I do some more hinting for this query? EDIT: I should also point out that the query's where clause uses the columns in IDX_MBR_IDENTFN and no columns other than what's in that index. So as far as I can tell, I'm not skipping any columns.

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• WPF Data virtualizing ListView

  - by Robert Jeppesen

  In our current WinForms app, we are displaying millions of records in ListView, using virtualization. Rows are loaded from DB as they are requested. This works well, with good performance. This is a showstopper for migrating to WPF for us. We need data virtualization in a ListView, like WinForms 2.0 has. Do you know a decent third-party control, or a relatively easy way of doing it with built-in controls? It doesn't need to be a DataGrid, a simple ListView will suffice. Note, I'm note talking about UI virtualization, it's data virtualization.

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