What should I do to solve this error in Qvector?

Yash001

@VRonin said in What should I do to solve this error in Qvector?:

Are you sure you need 8m data points all in ram at once?

Yes. I am plotting the graph in real time.

Thank you for providing nice implementation for large dataset. I do have few questions regarding your code.

using ItemMapType = typename std::conditional<sorted, QMap<KeyType, ContainerObject<ValueType> >, QHash<KeyType, ContainerObject<ValueType> > >::type;
            std::unique_ptr<ItemMapType> m_itemsMap;

I think HugeContainerData::std::unique_ptr<ItemMapType> m_itemsMap is storing all the key and position of value in "temp/"HugeContainerDataXXXXXX" file.

std::unique_ptr<QMap<qint64, bool> > m_memoryMap; is provide the information for value like value is store that particular location or not in "temp/"HugeContainerDataXXXXXX" file.

Could you correct me if i understood wrong in above two use?

if I understood correctly then I am missing something.
How do you save the space in RAM because of size of HugeContainerData::std::unique_ptr<ItemMapType> m_itemsMap is increase as per number of elements are increase.

Another few Question for creating Hugevector.

Is it good idea to create the HugeContainerData::Hugevector with help of HugeContainerData::HugeMap.?

like HugeContainerData::HugeMap <int, double>
Here "key" = index of Vector.
Value = vectore value.

or

Are you recommend to create separate implementation for Hugevector?

something like below:
modify the HugeContainerData::std::unique_ptr<ItemMapType>

using ItemMapType = typename std::conditional<sorted, QMap<KeyType, ContainerObject<ValueType> >, QHash<KeyType, ContainerObject<ValueType> > >::type;

to

using ItemMapType = typename std::conditional<sorted, QVectore<ContainerObject<ValueType> >, QList<ContainerObject<ValueType> > >::type;

ItemMapType will store only position of elements in temp/"HugeContainerDataXXXXXX" file.

Yash001

Here I implemented My HugeVector with help of https://github.com/VSRonin/QtHugeContainer

#pragma once
#ifndef hugecontainer_h__
#define hugecontainer_h__

#include <QDataStream>
#include <QDir>
#include <QDirIterator>
#include <qvector.h>
#include <QSharedData>
#include <QSharedDataPointer>
#include <QExplicitlySharedDataPointer>
#include <QTemporaryFile>
#include <QDebug>
#include <memory>
#include <initializer_list>


namespace HugeContainers {
	template <class ValueType>
	class HugeContainer;
}

template <class ValueType>
QDataStream& operator<<(QDataStream &out, const HugeContainers::HugeContainer<ValueType>& cont);

template <class ValueType>
QDataStream& operator>>(QDataStream &in, HugeContainers::HugeContainer<ValueType>& cont);


namespace HugeContainers {
	//! Removes any leftover data from previous crashes
	inline void cleanUp() {
		QDirIterator cleanIter{ QDir::tempPath(), QStringList(QStringLiteral("HugeContainerData*")), QDir::Files | QDir::Writable | QDir::CaseSensitive | QDir::NoDotAndDotDot };
		while (cleanIter.hasNext()) {
			cleanIter.next();
			QFile::remove(cleanIter.filePath());
		}

	}

	template <class ValueType>
	class HugeContainer
	{
		static_assert(std::is_default_constructible<ValueType>::value, "ValueType must provide a default constructor");
		static_assert(std::is_copy_constructible<ValueType>::value, "ValueType must provide a copy constructor");
	private:
		template <class ValueType>
		struct ContainerObjectData : public QSharedData
		{
			bool m_isAvailable;
			union ObjectData
			{
				explicit ObjectData(qint64 fp)
					:m_fPos(fp)
				{}
				explicit ObjectData(ValueType* v)
					:m_val(v)
				{}
				qint64 m_fPos;
				ValueType* m_val;
			} m_data;
			explicit ContainerObjectData(qint64 fp)
				:QSharedData()
				, m_isAvailable(false)
				, m_data(fp)
			{}
			explicit ContainerObjectData(ValueType* v)
				:QSharedData()
				, m_isAvailable(true)
				, m_data(v)
			{
				Q_ASSERT(v);
			}
			~ContainerObjectData()
			{
				if (m_isAvailable)
					delete m_data.m_val;
			}
			ContainerObjectData(const ContainerObjectData& other)
				:QSharedData(other)
				, m_isAvailable(other.m_isAvailable)
				, m_data(other.m_data.m_fPos)
			{
				if (m_isAvailable)
					m_data.m_val = new ValueType(*(other.m_data.m_val));
			}
		};

		template <class ValueType>
		class ContainerObject
		{
			QExplicitlySharedDataPointer<ContainerObjectData<ValueType> > m_d;
		public:
			explicit ContainerObject(qint64 fPos)
				:m_d(new ContainerObjectData<ValueType>(fPos))
			{}
			explicit ContainerObject(ValueType* val)
				:m_d(new ContainerObjectData<ValueType>(val))
			{}
			ContainerObject(const ContainerObject& other) = default;
			bool isAvailable() const { return m_d->m_isAvailable; }
			qint64 fPos() const { return m_d->m_data.m_fPos; }
			const ValueType* val() const { Q_ASSERT(m_d->m_isAvailable); return m_d->m_data.m_val; }
			ValueType* val() { Q_ASSERT(m_d->m_isAvailable); m_d.detach(); return m_d->m_data.m_val; }
			void setFPos(qint64 fp)
			{
				if (!m_d->m_isAvailable && m_d->m_data.m_fPos == fp)
					return;
				m_d.detach();
				if (m_d->m_isAvailable)
					delete m_d->m_data.m_val;
				m_d->m_data.m_fPos = fp;
				m_d->m_isAvailable = false;
			}
			void setVal(ValueType* vl)
			{
				m_d.detach();
				if (m_d->m_isAvailable)
					delete m_d->m_data.m_val;
				m_d->m_data.m_val = vl;
				m_d->m_isAvailable = true;
			}
		};


		template <class ValueType>
		class HugeContainerData : public QSharedData
		{
		public:
			using ItemMapType = QVector<ContainerObject<ValueType>>;
			std::unique_ptr<ItemMapType> m_itemsMap;
			std::unique_ptr<QMap<qint64, bool> > m_memoryMap;
			std::unique_ptr<QTemporaryFile> m_device;

			HugeContainerData()
				: QSharedData()
				, m_device(std::make_unique<QTemporaryFile>(QDir::tempPath() + QDir::separator() + QStringLiteral("HugeContainerDataXXXXXX")))
				, m_memoryMap(std::make_unique<QMap<qint64, bool> >())
				, m_itemsMap(std::make_unique<ItemMapType>())
			{
				if (!m_device->open())
					Q_ASSERT_X(false, "HugeContainer::HugeContainer", "Unable to create a temporary file");
				m_memoryMap->insert(0, true);
			}
			~HugeContainerData() = default;
			
			HugeContainerData(HugeContainerData& other)
				: QSharedData(other)
				, m_device(std::make_unique<QTemporaryFile>(QDir::tempPath() + QDir::separator() + QStringLiteral("HugeContainerDataXXXXXX")))
				, m_memoryMap(std::make_unique<QMap<qint64, bool> >(*(other.m_memoryMap)))
				, m_itemsMap(std::make_unique<ItemMapType>(*(other.m_itemsMap)))
			{
				if (!m_device->open())
					Q_ASSERT_X(false, "HugeContainer::HugeContainer", "Unable to create a temporary file");
				other.m_device->seek(0);
				qint64 totalSize = other.m_device->size();
				for (; totalSize > 1024; totalSize -= 1024)
					m_device->write(other.m_device->read(1024));
				m_device->write(other.m_device->read(totalSize));
			}

		};

		QExplicitlySharedDataPointer<HugeContainerData<ValueType>> m_d;


		qint64 writeInMap(const QByteArray& block) const
		{
			if (!m_d->m_device->isWritable())
				return -1;

			auto i = m_d->m_memoryMap->end()-1; // last value iterator
			if (i.value()) {
				m_d->m_memoryMap->insert(i.key() + block.size(), true);		
				i.value() = false;
				m_d->m_device->seek(i.key());
				if (m_d->m_device->write(block) >= 0)
					return i.key();
				return -1;
			}
			Q_UNREACHABLE();
			return 0;
		}

		void removeFromMap(qint64 pos) const {
			auto fileIter = m_d->m_memoryMap->find(pos);
			Q_ASSERT(fileIter != m_d->m_memoryMap->end());
			if (fileIter.value())
				return;
			fileIter.value() = true;
			m_d->m_memoryMap->erase(fileIter);
		}


	
		qint64 writeElementInMap(const ValueType& val) const
		{
			QByteArray block;
			{
				QDataStream writerStream(&block, QIODevice::WriteOnly);
				writerStream << val;
			}

			const qint64 result = writeInMap(block);
			return result;
		}


		bool saveQueue(const uint& index) const {
			bool allOk = false;
			auto valToWrite = m_d->m_itemsMap->begin() + index; 
			
			const qint64 result = writeElementInMap(*(valToWrite->val()));
			if (result >= 0) {
				valToWrite->setFPos(result);
				allOk = true;
			}
			return allOk;
		}

		bool enqueueValue(std::unique_ptr<ValueType>& val) const
		{
			m_d->m_itemsMap->push_back(ContainerObject<ValueType>(val.release()));
			if (saveQueue(size()-1)) {
				return true;
			}
		    return false;
		}

		std::unique_ptr<ValueType> valueFromBlock(const uint& index) const
		{
			QByteArray block = readBlock(index);
			if (block.isEmpty())
				return nullptr;
			auto result = std::make_unique<ValueType>();
			QDataStream readerStream(block);
			readerStream >> *result;
			return result;
		}

		QByteArray readBlock(const uint& index ) const
		{
			if (Q_UNLIKELY(!m_d->m_device->isReadable()))
				return QByteArray();
			m_d->m_device->setTextModeEnabled(false);
			
			auto itemIter = m_d->m_itemsMap->begin() + index;       //  get iterator at particular position
			Q_ASSERT(itemIter != m_d->m_itemsMap->end());
			Q_ASSERT(!itemIter->isAvailable());
			
			auto fileIter = m_d->m_memoryMap->constFind(itemIter->fPos());
			Q_ASSERT(fileIter != m_d->m_memoryMap->constEnd());
			if (fileIter.value())
				return QByteArray();
			
			auto nextIter = fileIter + 1;
			m_d->m_device->seek(fileIter.key());
			
			QByteArray result;
			if (nextIter == m_d->m_memoryMap->constEnd())
				result = m_d->m_device->readAll();
			else
				result = m_d->m_device->read(nextIter.key() - fileIter.key());
			
			return result;
		}


	public:

		HugeContainer()
			:m_d(new HugeContainerData<ValueType>{})
		{
		}

		HugeContainer(const HugeContainer& other) = default;
		HugeContainer& operator=(const HugeContainer& other) = default;
		HugeContainer& operator=(HugeContainer&& other) Q_DECL_NOTHROW {
			swap(other);
			return *this;
		}


		void swap(HugeContainer<ValueType>& other) Q_DECL_NOTHROW {
			std::swap(m_d, other.m_d);
		}

		
		void push_back(const ValueType &val) {
			m_d.detach();
			auto tempval = std::make_unique<ValueType>(val);
			enqueueValue(tempval);
		}
		
		void push_back(ValueType* val)
		{
			if (!val)
				return;
			m_d.detach();
			std::unique_ptr<ValueType> tempval(val);
			enqueueValue(tempval);
			
		}

		/*if index is not correct then append to the vector*/
		void insert(uint index, const ValueType &val) {

			if (!correctIndex(index))
				index = size();
		
			m_d.detach();
			auto tempval = std::make_unique<ValueType>(val);
			m_d->m_itemsMap->insert(index, ContainerObject<ValueType>(tempval.release()));
			saveQueue(index);
		}


		void insert(const uint& index, ValueType* val)
		{
			if (!val)
				return;

			if (!correctIndex(index))
				return;

			m_d.detach();
			std::unique_ptr<ValueType> tempval(val);

			m_d->m_itemsMap->insert(index, ContainerObject<ValueType>(tempval.release()));
			saveQueue(index);
		}


		/* Must be put correct index for finding value */
		const ValueType& at(const uint& index)
		{
			Q_ASSERT(!isEmpty());

			auto valueIter = m_d->m_itemsMap->begin() + index;
			Q_ASSERT(valueIter != m_d->m_itemsMap->end());
			
			auto result = valueFromBlock(index);
			Q_ASSERT(result);
			
			m_d.detach();
			return *(result.release());
		}

		bool removeAt(const uint& index)
		{
			if (!correctIndex(index))
				return false;
			m_d.detach();
			auto itemIter = m_d->m_itemsMap->begin() + index;
			Q_ASSERT(itemIter != m_d->m_itemsMap->end());
			removeFromMap(itemIter->fPos());
			m_d->m_itemsMap->erase(itemIter);
			return true;
		}

		void clear()
		{
			if (isEmpty())
				return;
			m_d.detach();
			if (!m_d->m_device->resize(0)) {
				Q_ASSERT_X(false, "HugeContainer::HugeContainer", "Unable to resize temporary file");
			}
			m_d->m_itemsMap->clear();
			m_d->m_memoryMap->clear();
			m_d->m_memoryMap->insert(0, true);
		}

		int count() const
		{
			return size();
		}
		int size() const
		{
			return m_d->m_itemsMap->size();
		}
		bool isEmpty() const
		{
			return m_d->m_itemsMap->isEmpty();
		}

		bool correctIndex(const uint& index) {
			return ((index >= 0) && (m_d->m_itemsMap->size() > index));
		}

		int memMapsize() const
		{
			return m_d->m_memoryMap->size();
		}

		inline const ValueType& first() const
		{
			Q_ASSERT(!isEmpty());
			return at(0);
		}

		inline ValueType& first()
		{
			Q_ASSERT(!isEmpty());
			return const_cast<ValueType&>(at(0));
		}

		inline const ValueType& last() const
		{
			Q_ASSERT(!isEmpty());
			return at(size() - 1);
		}

		inline ValueType& last()
		{
			Q_ASSERT(!isEmpty());
			return const_cast<ValueType&>(at(size() - 1));
		}
	    
	};

}
#endif // hugecontainer_h__

I test this code with help of

int main(int argc, char *argv[])
{
	QCoreApplication a(argc, argv);

	/*  create the funcation for checking the size of memory map*/
	HugeContainers::HugeContainer<qreal> obj;
	std::cout << "start executation";
	//QVector<qreal> obj;
	for (int i = 0; i < 9000000; i++) {
		try {
			obj.push_back(10.23);
			obj.push_back(10.23);
			obj.push_back(10.23);
			obj.push_back(10.23);
			obj.push_back(10.23);
			obj.push_back(10.23);
			obj.push_back(10.23);
			obj.push_back(10.23);
			obj.push_back(10.23);
		}
		catch (...) {
			std::cout << "value of i : " << i;
		}
	}
	std::cout << "stop executation";

	
	return a.exec();
}

I got same error bad_allocation.

I knew it is slow because of I did not add m_maxCache as @VRonin used in his code. I will add later if it is work fine.

anything do I need to modify?

Christian Ehrlicher

@Yash001 said in What should I do to solve this error in Qvector?:

9000000

You try to allocate 9000000 * 9 * 8Bytes = 648000000Bytes = ~617MB continuous memory which fails because your OS can't allocate it. Don't see what Qt can do against this. Esp.when your executable is a 32 Bit executable which seems to be the case.

JonB

@Yash001
So now the (probably better) question is why do you need 9 million elements in a QVector?

Yash001

@JonB said in What should I do to solve this error in Qvector?:

So now the (probably better) question is why do you need 9 million elements in a QVector?

Thank you for your time and help @JonB @Christian-Ehrlicher @VRonin @aha_1980 @J-Hilk

Just for testing purpose I took 9 million elements in Qvector.

My application could be run more than 2 hours on the user end. I don't know exact time. currently I can reach at near about 8 million * 9 (QVector) data points in 42 min.

one Qvector is pointing to X axis data on plot.
another Qvector is pointing to Y axis data on plot.

User can select the another vector for X and Y axis.

Just want to give more detail:

currently I am getting data point from device.
store into container.
read the last value from container.
put data point into csv file and plot.
User can select different container anytime.

any other better approach should I try?

something like change the design or something else.

is It worth to create temp file for memory map?

JonB

@Yash001
Well you now know that with your 32-bit compiled application you're not going to have enough contiguous memory for 9 million or whatever data points in memory. So what are you going to do about it? :) 9M is a lot of plot points!? Maybe you can discard old points, maybe you can thin out with sampling. Maybe you should make your app 64-bit and also buy more memory, but if you don't hit the limit at 9M maybe you'll find your data is even bigger and then what?

Yash001

@JonB said in What should I do to solve this error in Qvector?:

Maybe you should make your app 64-bit and also buy more memory,

I trying to build application in 64 bits and test it same things occur.

Is it worth to create the temp file for memory map and data?

memory map has position of value, which store in data file.
whenever I need to read the value , at that time with help memory-map file I do have address of data, and after that read the value from temp file.

to make more speed operation I should use large Queue<qreal>.
in starting phase few data point will store in queue if queue is full then write the full queue in files.

I did not have clear though about reading operation for making speed up from index.

Christian Ehrlicher

Nobody will take a look at 9 Million data points... thin them out with sampling.

JonB

@Yash001
As @Christian-Ehrlicher & I have suggested, maybe you should really be down-sampling to reduce your data points.

Having said that, if you are saying that a properly-compiled 64-bit now bombs out in the same way as 32-bit at what we think is only half a gig of so of memory on a machine with plenty of free RAM, something sounds wrong there. You could do some more investigations on the machine, seeing how much you are really allocating and how much free memory you are able to access. I would want to understand that before I figured what I need to save away to file or whatever.

Yash001

@JonB said in What should I do to solve this error in Qvector?:

if you are saying that a properly-compiled 64-bit now bombs out in the same way as 32-bit at what we think is only half a gig of so of memory on a machine with plenty of free RAM,

earlier I was doing mistake while creating 64 bit application version. I am using visual studio while creating 64 bit application I was just copied all setting of 32 bit application, So That in Solution platform it was showing x64 but it was creating 32 bit executable file.

I created 64 bit application version, which is save very large amount of data in RAM.

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What should I do to solve this error in Qvector?