[Class 12] Google Open Sources Abseil, a Collection of C++ and Python Utilities

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Google has made available a number of C++ libraries they use internally for many of their projects. Python ones are to follow soon.
Google has developed Abseil over a decade in order to support the needs of their programmers working on various projects including Protocol Buffers, gRPC, or TensorFlow. Google even says that Abseil is:
a collection of libraries drawn from the most fundamental pieces of Google’s internal codebase. These libraries are the nuts-and-bolts that underpin almost everything that Google runs. Bits and pieces of these APIs are embedded in most of our open source projects, and now we have brought them together into one comprehensive project.
Abseil encompasses the most basic building blocks of Google’s codebase: code that is production tested and will be fully maintained for years to come.
Abseil includes abstractions that initially were not part of C++14 or C++17, but some of them ended up being included in the standard. For example, Google had a type called StringPiece.Later, C++ 17 added a similar type called std::string_view, and Google has reworked StringPiece into absl::string_view to have the same API as the newly C++ 17 type. Under the hood, Abseil’s string_view defaults to the standard implementation if the developer is using C++ 17 or to Google’s implementation if using a previous C++ version.
The benefit of using Abseil is having access to C++ features not existing in the standard yet, with the promise that Google will rework them to default to the standard when included in it. Google encourages developers to adopt Abseil, mentioning that they have over 250M lines of C++ code that uses it and almost every project builds from the head. That means Abseil is very used by Google and constantly maintained to keep up with the needs of their projects. 
Abseil includes the following libraries:
  • base - initialization and other basic code.
  • algorithm - additions to the C++ <algorithm> library and container-based versions of such algorithms.
  • container - additional STL-style containers.
  • debugging – debugging library used to check for leaks.
  • memory – includes C++11-compatible versions of std::make_unique()and memory management.
  • meta – includes C++11-compatible versions of type checks available within C++14 and C++17 versions of the C++ <type_traits> library.
  • numeric - C++11-compatible 128-bit integers.
  • strings – various string utilities.
  • synchronization - concurrency primitives and synchronization abstractions.
  • time - abstractions for working with absolute points in time, time durations, and time zones.
  • types - non-container utility types.
The code has been licensed under the Apache license and it is available on GitHub. A Python version of the library is to be made available soon. 

How to use Essay Writing Services

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Chapter-1 Indus valley Civilization CLass Notes

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CHAPTER I
The HarappanCivilisation

1.       WHAT ARE THE SOURCES AVAILABLE TO UNDERSTAND (OR) TO STUDY HARAPPAN CIVILIZATION?

a)    The Harappan seal is possibly the most distinctive artifact of the Harappans or Indus valley civilisation. Harappan seals contain animal and plant motifs and signs from a script that remains undeciphered.
b)    We know a great deal of sources which were left by the people, such as their houses, pots, ornaments, tools, and seals – in other words, archaeological evidence.

2.       *WHY WAS INDUS VALLEY CIVILISATIONALSO CALLED THE HARAPPAN CULTURE?

a.       Archaeologists use the term “culture” for a group of objects, distinctive in style, that are usually found together within a specific geographical area and period of time.
b.      In the case of the Harappan culture, these distinctive objects include seals, beads, weights, stone blades and baked bricks.
c.       These objects were found from areas as far apart as Afghanistan, Jammu, Baluchistan (Pakistan) and Gujarat .
d.      Harappan civilisation is dated between c. 2600 and1900 BCE.

3.      Similarities and DIFFERENCES BETWEEN EARLY HARAPPAN CULTURES AND Mature Harappan CULTURES.

a)    Early and later Harappan cultures were associated with distinctive pottery, evidence of agriculture and pastoralism, and some crafts.
b)    In Early Harappan cultures, Settlements were generally small, and there were virtually no large buildings. But in Mature Harappan culture settlements were large and buildings were also large.

4.       SUBSISTENCE STRATEGIES (DIETARY PRACTICES) OF HARAPPAN CULTURES AND MATURE HARAPPAN CULTURES

a.     The Harappans ate a wide range of plant products. Archaeologists have been able to reconstruct dietary practices from finds of charred grains, seeds and bones.
b.    These are studied by archaeo-botanists, who are specialists in ancient plant remains.
c.    Food grains found at Harappan sites include wheat, barley, lentil, chickpea, sesame, Millets and rice.
d.    The Harappans ate a wide range of animal products.Archaeologists have been able to reconstruct use of animals from finds of charred animal bones found at Harappan sites. These include those of cattle, sheep,goat, buffalo and pig.
e.    These are studied by Archaeo-zoologists or zoo-Archaeologists who are specialists in ancient animal remains.
f.     Bones of wild species such as boar, deer and gharial were also found. We do not know whether the Harappans hunted these animals themselves orobtained meat from other hunting (tribal) communities.



5. PREVALENCE OFAGRICULTURE IN HARAPPAN CIVILISATION

A.      Representations on seals and terracotta sculpture indicate that the bull was known, and oxen were used for plowing.
B.      Terracotta models of the plough have been found at sites in the Cholistan and at Banawali (Haryana).
C.      Archaeologists have also found evidence of a ploughed field at Kalibangan (Rajasthan).The field had two sets of furrows at right angles to each other, suggesting that two different crops were grown together.
d.    Archaeologists have also identified the tools used for harvesting. Harappans used stone blades set with wooden handles and metal tools made of copper.
e.    Most Harappan sites are located in semi-aridlands, where irrigation was probably required foragriculture. Traces of canals, water reservoirs and wells have been found at the Harappan sites indicate that agriculture was practiced.
f.     Archaeologists have also found charred food grains which indicate prevalence of agriculture.

6.       UNIQUE FEATURES OF MOHENJODARO

A.DIVISIONS IN MOHENJODARO CITY

a.    The settlement is divided into two sections, one smaller but higher called as the Citadel and the other much larger but lower called the Lower Town.
b.    The Citadel owesits height to the fact that buildings were constructedon mud brick platforms. It was walled and physically separated from theLower Town. We find evidence of structures that were probably used for special public purposes.
B.CITADEL
c.    The warehouse, a massive structure of which the lower brick portions remain, while the upper portions, probably of wood, decayed long ago.
d.    The Great Bath was a large rectangular tank in a courtyard surrounded by a corridor on all four sides. There were two flights of steps on the north and south leading into the tank. There were rooms on three sides, in one of which was a large well. Across a lane to the north lay a smaller building with eight bathrooms, four on each side of a corridor.Scholars suggest that it was meant for some kind of a special ritual bath.

C. LOWER TOWN

E.      The Lower Town was also walled. Several buildingswere built on platforms, which served as foundations.
F.      Once the platforms were in place, all building activity within the city was restricted to a fixed area on the platforms. So it seems that the settlement was first planned and then built accordingly.

D.DRAINAGE SYSTEM

G.     One of the most distinctive features of Harappan cities was the carefully planned drainage system. If you look at the plan of the Lower Town you will noticethat roads and streets were laid out along an approximate “grid” pattern, intersecting at right angles.
H.     It seems that streets with drains were laidout first and then houses were built along them.

E.DOMESTIC ARCHITECTURE
I.        The Lower Town at Mohenjodaro provides examples of residential buildings. Many were centred on a courtyard, with rooms on all sides. The courtyardwas probably the centre of activities such as cooking and weaving, particularly during hot and dry weather. People were more concern for privacy: there are no windows in thewalls along the ground level. Besides, the mainentrance does not give a direct view of the interioror the courtyard.
J.       Every house had its own bathroom paved withbricks, with drains connected through the wall tothe street drains. Some houses have remains of stair cases to reach a second storey or the roof. Many houses had wells, often in a room that could be reached from the outside and perhaps used by passers-by.

7.     STRATEGIES TOFIND OUT WHETHER THERE WERE SOCIAL OR ECONOMICDIFFERENCES AMONGST PEOPLE LIVING WITHIN HARAPPAN CULTURE.

a.    At burials in Harappan sites the dead weregenerally laid in pits. Sometimes, there weredifferences in the way the burial pit was made – insome instances; the hollowed-out spaces were linedwith bricks. These variations are an indicationof social differences.

b.    Some graves contain pottery and ornaments,perhaps indicating a belief that these could be used in the afterlife. Jewellery has been found in burialsof both men and women.

c.    Inthe cemetery found in Harappa in the mid-1980s, a burial contained ornament consisting of three shell rings, a jasper bead and hundreds of micro beads were found near the skull of a male.In some instances the dead were buried with coppermirrors. But the Harappans did not believe in burying precious thingswith the dead.

d.    Another strategy to identify social differences is to study artefacts, which archaeologists broadly classify as utilitarian and luxuries. The first categoryincludes objects of daily use made of stone or clay such as querns, pottery, needles, flesh-rubbers are usually found distributed throughout settlements.

e.    Archaeologists assume luxuries objects are rare and made from costly, non-local materials or with complicated technologies such as little pots of faience, beads, micro beads etc were probably consideredprecious because they were difficult to make.Rare objects made of valuable materialsare generally concentrated in large settlements like Mohenjodaro and Harappa

8.       CRAFTPRODUCTION IN INDUS VALLEY

a.    Mohenjodaro almost exclusively devoted to craft production, including bead-making,shell-cutting, metal-working, seal-making andweight-making.
b.    The variety of raw materials used to make crafts such as stones (carnelian - red stone, jasper-yellow stone, crystal- colourless stone, quartz and steatite) metals(copper, bronze and gold) shell and clay.
c.    The shapes of crafts were numerous – discshaped,cylindrical, spherical, barrel-shaped,segmented. Some were decorated by incising orpainting, and some had designs etched onto them. Some beads were made oftwo or more stones, cemented together, some of stones were decorated with gold caps
d.    Techniques for making beads differed according to the material Moulding, chipping,Grinding, polishing and drilling are some of the techniques used for making crafts.
e.    Chanhudaro, Lothal,Dholavira,Nageshwar and Balakot are some of the craft centres.

9.     HOW DID ARCHAEOLOGISTS IDENTIFY CENTRESOF PRODUCTION?

a.    In order to identify centres of craft production, archaeologists usually look for the following: raw material such as stone nodules, whole shells, and copperore etc.
b.    Archaeologists also lookfor tools which were used for making crafts.
c.    Archaeologists lookfor unfinished objects, rejects and waste material. Waste isone of the best indicatorsof craft work. Sometimes, larger waste pieces were used up tomake smaller objects.
d.    These traces suggestthat apart from small, specializedcenters, craftproduction was also undertaken in large cities such as Mohenjodaro and Harappa.

10.    STRATEGIES FOR PROCURING RAW MATERIALS WITH IN THE SUB-CONTINENT

Transportation:
a.     Terracotta toy models of bullock carts suggest that this was one important means of transporting goods and people across land routes.
b.    Depictions of shipsand boats on seals suggest that Riverine routes along the Indus and its tributaries, as well as coastal routes were also probably used for transporting goods and people.

Strategies for ProcuringMaterials

a.       The Harappans procured materials for craftproduction in various ways. For instance, theyestablished settlements where raw material was available.(Nageshwar andBalakot- shell, Shortughai- lapis lazuli, a blue stone, Lothal- carnelian, steatite and metal-Rajasthan and Gujarat)
b.      Another strategy for procuring raw materials mayhave been to send expeditions to areas such as the Khetri region of Rajasthan (for copper) and southIndia (for gold). These expeditions establishedcommunication with local communities.
c.       Occasional finds of Harappan artefacts such as steatite micro beads in the Khetri area indicates that the inhabitants of Ganeshwar-Jodhpura culture supplied copper to the Harappans according to the aggrement.
(What is Ganeshwar-Jodhpura culture?-In the Khetri area archaeologists found a new culture and call it as the Ganeshwar-Jodhpura culture. Here they found distinctive non-Harappan pottery and an unusual wealth of copper objects. It is possiblethat the inhabitants of this region supplied copper to the Harappans).
STRATEGIES FOR PROCURINGMATERIALS FROM DISTANT LANDS

a.    Recent archaeological finds suggest that copper wasalso probably brought from Oman, on the southeasterntip of the Arabian Peninsula. Chemicalanalyses have shown that both the Omani copper and Harappan copper artifacts have traces of nickel.
b.    A distinctive type of vessel, a large Harappan jar coated with a thick layer of blackclay has been found at Omani sites. Itis possible that the Harappans exchanged the contents of these vessels for Omani copper.
c.    Mesopotamian texts datable to the thirdmillennium BCE refer to copper coming from a region called Magan, perhaps a name forOman, and interestingly enough copper found Mesopotamian sites alsocontains traces of nickel.
d.    It is worth notingthat Mesopotamian textsmention contact with regions named Dilmun(Bahrain), Magan and Meluhha (the Harappan region).They mention the products from Meluhha: carnelian, lapis lazuli, copper, gold, and varieties of wood.
e.    A Mesopotamian myth says of Meluhha: “May your bird be the haja-bird, may its call be heard inthe royal palace.” Some archaeologists think the haja-bird was the peacock.
f.     Mesopotamian texts refer to Meluhha (the Harappan region) as aland of seafarers. Besides,we find depictions of shipsand boats on seals.

HARAPPAN SEALS
a.    Seals and sealings were used to facilitate longdistancecommunication. Imagine a bag of goodsbeing sent from one place to another. Its mouth wastied with rope and on the knot was affixed some wetclay on which one or more seals were pressed,leaving an impression.
b.     If the bag reached withits sealing intact, it meant that it had not beentampered with. The sealing also conveyed the identityof the sender.
c.    Harappan seals usually have a line of writing and animal midifs. Scholars have also suggested that the motif(generally an animal) conveyed a meaning to thosewho could not read.

HARAPPANSCRIPT
a.    Harappan seals usually have a line of writing. Most inscriptions are short, the longest containing about 26 signs. Although the script remains undeciphered to date, it was evidently notalphabetical but syllable.It has just too many signs –somewhere between 375 and 400.
b.     It is apparent that the script was written from right to left as some seals show a wider spacing on the right and crampingon the left, as if the engraver began working fromthe right and then ran out of space.
c.    A variety of objects on which writinghas been found: seals, copper tools, rims of jars,copper and terracotta tablets, jewellery, bone rods, even an ancient signboard. Remember, there mayhave been writing on perishable materials too such as cloth, animal skin etc.

HARAPPANWEIGHTS
a.    Exchanges were regulated by a precise system ofweights, usually made of a stone called chert and generally cubical with no markings.
b.    Thelower denominations of weights were binary (1, 2, 4,8, 16, 32, etc). while the higherdenominations followed the decimal system. Thesmaller weights were probably used for weighing jewellery and beads and bigger weights were used for food grains.
c.    Metal scale-pans have alsobeen found. These were probably used for measuring cloth and other materials.
Ruling Authority in indus valley civilisation

(What are indications prove that complex decisions were taken and implemented in Harappan society by the ruler?)

a.    The extraordinary uniformity of Harappan artefacts as evident in pottery, seals and weights.
b.    Bricks, thoughobviously not produced in any single centre, were ofa uniform ratio throughout the region, from Jammuto Gujarat.
c.    We have also seen that settlements werestrategically set up in specific locations for variousreasons.
d.    Labour was mobilised for makingbricks and for the construction of massive wallsand platforms.
e.    Who organised these activities? Most probably the king.

RULING AUTHORITY OR CENTRE OF POWER

a.    A large building found at Mohenjodaro was labelled as a palace byarchaeologists but no spectacular finds wereassociated with it.
b.     A stone statue was labelled and continues to be known as the “priest-king”. This isbecause archaeologists were familiar withMesopotamian history and its “priest-kings”
c.    Some archaeologists are of the opinion that Harappan society had no rulers, and that everybody enjoyed equal status( Democracy)
d.     Other archaeologistsfeel thatthere was no singleruler but several, that Mohenjodaro had a separate ruler, Harappa another, and so forth.
e.    Yet other archaeologistsargue that there was a single state and single ruler because of  the similarity in artefacts, the evidence for plannedsettlements, the standardized ratio of brick size, andthe establishment of settlements near sources of rawmaterial.

The End of the Civilisation

a.    There is evidence that by c. 1800 BCE most of the Mature Harappan sites had been abandoned. Simultaneously, there wasan expansion of population into newsettlements in Gujarat, Haryana andwestern Uttar Pradesh.
b.    Distinctive artefacts of the civilisation- weights, seals, special beads, Writing, long-distance trade, andcraft specialization disappeared after 1800 BCE.Houseconstruction techniques deterioratedand large public structures were nolonger produced.
c.    Overall disappearence of artefacts and settlements indicates a rural wayof life in what is called Vedic culture  or vedic  civilisation began.
d.    Several explanations havebeen put forward. These range fromclimatic change, deforestation,excessive floods, the shifting and/or drying up ofrivers, to overuse of the landscape.
e.      Some of these“causes” may hold for certain settlements, but theydo not explain the collapse of the entire civilisation.It appears that a strong unifying element, perhaps the Harappan state, came to an end.

Evidence of an “invasion”in Indus valley civilisation

a.       Deadman Lane is a narrow valley wherepart of a skull, the bones of the thorax andupper arm of an adult were discovered.Allwerein very friable condition, at a depth of4 ft 2 in. The body lay on its back diagonally across the lane. Fifteen inches to thewest were a few fragments of a tiny skull. It is to these remains that the lane owesits name.
b.       Sixteen skeletons of people with the ornaments that they were wearing when theydied were found from the same part of Mohenjodaro in 1925.
c.       R.E.M. Wheeler, then Director-General of the ASI, tried tocorrelate this archaeological evidence with that of the Rigveda, the earliest known text in the subcontinent.
d.       There is no destruction level covering the latest period of the city Mohenjodaro, no sign of extensive burning, no bodies of warriors clad in armour and surrounded by the weapons of war. The citadel, the only fortified part of the city,yielded no evidence of a final defence.

Discovering the HarappanCivilisation
(How have archaeologistsused evidence from material remains topiece together parts of a fascinating harappan history?) OR (Howdid archaeologists “discover” the Harappan civilization?)

a.    Cunningham’s confusion

Cunningham, the first Director-General of theASI, began archaeological excavations in the midnineteenthcentury. Cunningham’s maininterest was in the archaeology of the Early Historic(c. sixth century BCE-fourth century CE) and laterperiods. He used the accounts left by ChineseBuddhist pilgrims who had visited the subcontinentbetween the fourth and seventh centuries CE to locateearly settlements.

Harappan artefacts were found fairly often duringthe nineteenth century and some of these reachedCunningham, he did not realise how old these were. A Harappan seal was given to Cunningham by anEnglishman. He noted the object, but unsuccessfullytried to place it within the time-frame of c. sixth century BCE-fourth century CE.It is not surprising that he missedthe significance of Harappa.

b.    John Marshall`s Ignorance

John Marshall , the Director-General of the marked a major change in Indianarchaeology. He was the first professionalarchaeologist to work in India, and brought hisexperience of working in Greece and Crete to thefield. He was interested in spectacular finds and patterns of everyday life.

Marshall tended to excavate along regularhorizontal units, measured uniformly throughout themound, ignoring the stratigraphy of the site. Thismeant that all the artefacts recovered from the sameunit were grouped together, even if they were foundat different stratigraphic layers. As a result, valuable information about Harappan civilisation was irretrievably lost.

c.    R.E.M. Wheeler`s problems

R.E.M. Wheeler, took over as Director-General of the ASI in 1944, who rectified many problems. Wheeler recognised that it was necessaryto follow the stratigraphy of the mound ratherthan dig mechanically along uniform horizontallines. Moreover, as an ex-army brigadier, he broughtwith him a military precision to the practiceof archaeology.

However, with the partition of thesubcontinent and the creation of Pakistan, the majorsites are now in Pakistani territory. This has spurredIndian archaeologists to try and locate sites in India.

d.    Daya Ram Sahni

Seals were discovered at Harappa by archaeologists such as Daya Ram Sahni in the early
decades of the twentieth century, in layers that weredefinitely much older than Early Historic levels. Itwas then that their significance began to be realised.

e.    Rakhal Das Banerji

Another archaeologist, Rakhal Das Banerji found similar seals at Mohenjodaro, leading to the
conjecture that these sites were part of a single archaeological culture. Based on these finds, in 1924,John Marshall, Director-General of the ASI,announced the discovery of a new civilisation in the Indus valley to the world.

f.     S.N. Roy

As S.N. Roy noted inThe Story of Indian Archaeology, “Marshall left Indiathree thousand years older than he had found her.”This was because similar, till-then-unidentifiedseals were found at excavations at Mesopotamiansites. It was then that the world knew not only of anewcivilisation, but also of one contemporaneouswith Mesopotamia.

Since the 1980s, there has also been growing international interest in Harappan archaeology.
Specialists from the subcontinent and abroad havebeen jointly working at both Harappa and Mohenjodaro. They are using modern scientifictechniques including surface exploration to recovertraces of clay, stone, metal and plant and animalremains as well as to minutely analyse every scrap of available evidence. These explorations promise toyield interesting results in the future.

How does material evidence allow the  archaeologiststobetter reconstruct Harappan life?.

1.    Recovering artefacts is just the beginning of the archaeological enterprise. Archaeologists thenclassify their finds. One simple principle ofclassification is in terms of material, such as stone,clay, metal, bone, ivory, etc.
2.     The second, and morecomplicated, is in terms of function: archaeologistshave to decide whether, for instance, an artefact is a tool or an ornament, or both, or something meantfor ritual use.
3.    An understanding of the function of an artifact is often shaped by its resemblance with present-daythings – beads, querns, stone blades and pots are obvious examples.
4.    Archaeologists also try to identifythe function of an artefact by investigating the context in which it was found: was it found in ahouse, in a drain, in a grave, in a kiln?
5.    Sometimes, archaeologists have to take recourseto indirect evidence. For instance, though there aretraces of cotton at some Harappan sites, to find outabout clothing we have to depend on indirectevidence including depictions in sculpture.

What were the problems of archaeological interpretation to reconstruct religious practices of the Harappans?

a.     Early archaeologists thought thatcertain objects which seemed unusual or unfamiliarmay have had a religious significance. These includedterracotta figurines of women, heavily jewelled, some with elaborate head-dresses. These were regardedas mother goddesses.
b.    Rare stone statuary of men in an almost standardised posture, seated with onehand on the knee – such as the “priest-king” – wasalso similarly classified.
c.    In other instances, structures have been assigned ritual significance.These include the Great Bath and fire altars found at Kalibangan and Lothal.
d.    Attempts have also been made to reconstructreligious beliefs and practices by examining seals,some of which seem to depict ritual scenes. Others,with plant motifs, are thought to indicate nature worship. Some animals – such as the one-hornedanimal, often called the “unicorn” – depicted on sealsseem to be mythical, composite creatures.
e.    In someseals, a figure shown seated cross-legged in a “yogic”posture, sometimes surrounded by animals, hasbeen regarded as a depiction of “proto-Shiva”, thatis, an early form of one of the major deities ofHinduism. Besides, conical stone objects have been classified as lingas.
f.        Many reconstructions of Harappan religion are made on the assumption