Home > Articles

This chapter is from the book

This chapter is from the book

Vector Data Types

For the scalar integer and floating-point data types described in Table 4.1, OpenCL C adds support for vector data types. The vector data type is defined with the type name, that is, char, uchar, short, ushort, int, uint, float, long, or ulong followed by a literal value n that defines the number of elements in the vector. Supported values of n are 2, 3, 4, 8, and 16 for all vector data types. Optionally, vector data types are also defined for double and half. These are available only if the device supports the double-precision and half-precision extensions. The supported vector data types are described in Table 4.2.

Table 4.2. Built-In Vector Data Types



char n

A vector of n 8-bit signed integer values

uchar n

A vector of n 8-bit unsigned integer values

short n

A vector of n 16-bit signed integer values

ushort n

A vector of n 16-bit unsigned integer values

int n

A vector of n 32-bit signed integer values

uint n

A vector of n 32-bit unsigned integer values

long n

A vector of n 64-bit signed integer values

ulong n

A vector of n 64-bit unsigned integer values

float n

A vector of n 32-bit floating-point values

double n

A vector of n 64-bit floating-point values

half n

A vector of n 16-bit floating-point values

Variables declared to be a scalar or vector data type are always aligned to the size of the data type used in bytes. Built-in data types must be aligned to a power of 2 bytes in size. A built-in data type that is not a power of 2 bytes in size must be aligned to the next-larger power of 2. This rule does not apply to structs or unions.

For example, a float4 variable will be aligned to a 16-byte boundary and a char2 variable will be aligned to a 2-byte boundary. For 3-component vector data types, the size of the data type is 4 x sizeof(component). This means that a 3-component vector data type will be aligned to a 4 x sizeof(component) boundary.

The OpenCL compiler is responsible for aligning data items appropriately as required by the data type. The only exception is for an argument to a kernel function that is declared to be a pointer to a data type. For such functions, the compiler can assume that the pointee is always appropriately aligned as required by the data type.

For application convenience and to ensure that the data store is appropriately aligned, the data types listed in Table 4.3 are made available to the application.

Table 4.3. Application Data Types

Type in OpenCL Language

API Type for Application























char n

cl_char n

uchar n

cl_uchar n

short n

cl_short n

ushort n

cl_ushort n

int n

cl_int n

uint n

cl_uint n

long n

cl_long n

ulong n

cl_ulong n

float n

cl_float n

double n

cl_double n

half n

cl_half n

Vector Literals

Vector literals can be used to create vectors from a list of scalars, vectors, or a combination of scalar and vectors. A vector literal can be used either as a vector initializer or as a primary expression. A vector literal cannot be used as an l-value.

A vector literal is written as a parenthesized vector type followed by a parenthesized comma-delimited list of parameters. A vector literal operates as an overloaded function. The forms of the function that are available are the set of possible argument lists for which all arguments have the same element type as the result vector, and the total number of elements is equal to the number of elements in the result vector. In addition, a form with a single scalar of the same type as the element type of the vector is available. For example, the following forms are available for float4:

(float4)( float, float, float, float )
(float4)( float2, float, float )
(float4)( float, float2, float )
(float4)( float, float, float2 )
(float4)( float2, float2 )
(float4)( float3, float )
(float4)( float, float3 )
(float4)( float )

Operands are evaluated by standard rules for function evaluation, except that no implicit scalar widening occurs. The operands are assigned to their respective positions in the result vector as they appear in memory order. That is, the first element of the first operand is assigned to result.x, the second element of the first operand (or the first element of the second operand if the first operand was a scalar) is assigned to result.y, and so on. If the operand is a scalar, the operand is replicated across all lanes of the result vector.

The following example shows a vector float4 created from a list of scalars:

float4  f = (float4)(1.0f, 2.0f, 3.0f, 4.0f);

The following example shows a vector uint4 created from a scalar, which is replicated across the components of the vector:

uint4   u = (uint4)(1); // u will be (1, 1, 1, 1)

The following examples show more complex combinations of a vector being created using a scalar and smaller vector types:

float4  f = (float4)((float2)(1.0f, 2.0f), (float2)(3.0f, 4.0f));
float4  f = (float4)(1.0f, (float2)(2.0f, 3.0f), 4.0f);

The following examples describe how not to create vector literals. All of these examples should result in a compilation error.

float4  f = (float4)(1.0f, 2.0f);
float4  f = (float2)(1.0f, 2.0f);
float4  f = (float4)(1.0f, (float2)(2.0f, 3.0f));

Vector Components

The components of vector data types with 1 to 4 components (aka elements) can be addressed as <vector>.xyzw. Table 4.4 lists the components that can be accessed for various vector types.

Table 4.4. Accessing Vector Components

Vector Data Types

Accessible Components

char2, uchar2, short2, ushort2, int2, uint2, long2, ulong2, float2


char3, uchar3, short3, ushort3, int3, uint3, long3, ulong3, float3


char4, uchar4, short4, ushort4, int4, uint4, long4, ulong4, float4


double2, half2


double3, half3


double4, half4


Accessing components beyond those declared for the vector type is an error. The following describes legal and illegal examples of accessing vector components:

float2 pos;
pos.x = 1.0f; // is legal
pos.z = 1.0f; // is illegal

float3 pos;
pos.z = 1.0f; // is legal
pos.w = 1.0f; // is illegal

The component selection syntax allows multiple components to be selected by appending their names after the period (.). A few examples that show how to use the component selection syntax are given here:

float4 c;

c.xyzw = (float4)(1.0f, 2.0f, 3.0f, 4.0f);
c.z = 1.0f;
c.xy = (float2)(3.0f, 4.0f);
c.xyz = (float3)(3.0f, 4.0f, 5.0f);

The component selection syntax also allows components to be permuted or replicated as shown in the following examples:

float4 pos = (float4)(1.0f, 2.0f, 3.0f, 4.0f);
float4 swiz = pos.wzyx; // swiz = (4.0f, 3.0f, 2.0f, 1.0f)
float4 dup = pox.xxyy;  // dup = (1.0f, 1.0f, 2.0f, 2.0f)

Vector components can also be accessed using a numeric index to refer to the appropriate elements in the vector. The numeric indices that can be used are listed in Table 4.5.

Table 4.5. Numeric Indices for Built-In Vector Data Types

Vector Components

Usable Numeric Indices


0, 1


0, 1, 2


0, 1, 2, 3


0, 1, 2, 3, 4, 5, 6, 7


0, 1, 2, 3, 4, 5, 6, 7, 8, 9, a, A, b, B, c, C, d, D, e, E, f, F

All numeric indices must be preceded by the letter s or S. In the following example f.s0 refers to the first element of the float8 variable f and f.s7 refers to the eighth element of the float8 variable f:

float8 f

In the following example x.sa (or x.sA) refers to the eleventh element of the float16 variable x and x.sf (or x.sF) refers to the sixteenth element of the float16 variable x:

float16 x

The numeric indices cannot be intermixed with the .xyzw notation. For example:

float4 f;
float4 v_A = f.xs123;  // is illegal
float4 v_B = f.s012w;  // is illegal

Vector data types can use the .lo (or .odd) and .hi (or .even) suffixes to get smaller vector types or to combine smaller vector types into a larger vector type. Multiple levels of .lo (or .odd) and .hi (or .even) suffixes can be used until they refer to a scalar type.

The .lo suffix refers to the lower half of a given vector. The .hi suffix refers to the upper half of a given vector. The .odd suffix refers to the odd elements of a given vector. The .even suffix refers to the even elements of a given vector. Some examples to illustrate this concept are given here:

float4 vf;

float2 low = vf.lo;    // returns vf.xy
float2 high = vf.hi;   // returns vf.zw
float x = low.low;     // returns low.x
float y = low.hi;      // returns low.y

float2 odd = vf.odd;   // returns vf.yw
float2 even = vf.even; // returns vf.xz

For a 3-component vector, the suffixes .lo (or .odd) and .hi (or .even) operate as if the 3-component vector were a 4-component vector with the value in the w component undefined.

InformIT Promotional Mailings & Special Offers

I would like to receive exclusive offers and hear about products from InformIT and its family of brands. I can unsubscribe at any time.


Pearson Education, Inc., 221 River Street, Hoboken, New Jersey 07030, (Pearson) presents this site to provide information about products and services that can be purchased through this site.

This privacy notice provides an overview of our commitment to privacy and describes how we collect, protect, use and share personal information collected through this site. Please note that other Pearson websites and online products and services have their own separate privacy policies.

Collection and Use of Information

To conduct business and deliver products and services, Pearson collects and uses personal information in several ways in connection with this site, including:

Questions and Inquiries

For inquiries and questions, we collect the inquiry or question, together with name, contact details (email address, phone number and mailing address) and any other additional information voluntarily submitted to us through a Contact Us form or an email. We use this information to address the inquiry and respond to the question.

Online Store

For orders and purchases placed through our online store on this site, we collect order details, name, institution name and address (if applicable), email address, phone number, shipping and billing addresses, credit/debit card information, shipping options and any instructions. We use this information to complete transactions, fulfill orders, communicate with individuals placing orders or visiting the online store, and for related purposes.


Pearson may offer opportunities to provide feedback or participate in surveys, including surveys evaluating Pearson products, services or sites. Participation is voluntary. Pearson collects information requested in the survey questions and uses the information to evaluate, support, maintain and improve products, services or sites, develop new products and services, conduct educational research and for other purposes specified in the survey.

Contests and Drawings

Occasionally, we may sponsor a contest or drawing. Participation is optional. Pearson collects name, contact information and other information specified on the entry form for the contest or drawing to conduct the contest or drawing. Pearson may collect additional personal information from the winners of a contest or drawing in order to award the prize and for tax reporting purposes, as required by law.


If you have elected to receive email newsletters or promotional mailings and special offers but want to unsubscribe, simply email information@informit.com.

Service Announcements

On rare occasions it is necessary to send out a strictly service related announcement. For instance, if our service is temporarily suspended for maintenance we might send users an email. Generally, users may not opt-out of these communications, though they can deactivate their account information. However, these communications are not promotional in nature.

Customer Service

We communicate with users on a regular basis to provide requested services and in regard to issues relating to their account we reply via email or phone in accordance with the users' wishes when a user submits their information through our Contact Us form.

Other Collection and Use of Information

Application and System Logs

Pearson automatically collects log data to help ensure the delivery, availability and security of this site. Log data may include technical information about how a user or visitor connected to this site, such as browser type, type of computer/device, operating system, internet service provider and IP address. We use this information for support purposes and to monitor the health of the site, identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents and appropriately scale computing resources.

Web Analytics

Pearson may use third party web trend analytical services, including Google Analytics, to collect visitor information, such as IP addresses, browser types, referring pages, pages visited and time spent on a particular site. While these analytical services collect and report information on an anonymous basis, they may use cookies to gather web trend information. The information gathered may enable Pearson (but not the third party web trend services) to link information with application and system log data. Pearson uses this information for system administration and to identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents, appropriately scale computing resources and otherwise support and deliver this site and its services.

Cookies and Related Technologies

This site uses cookies and similar technologies to personalize content, measure traffic patterns, control security, track use and access of information on this site, and provide interest-based messages and advertising. Users can manage and block the use of cookies through their browser. Disabling or blocking certain cookies may limit the functionality of this site.

Do Not Track

This site currently does not respond to Do Not Track signals.


Pearson uses appropriate physical, administrative and technical security measures to protect personal information from unauthorized access, use and disclosure.


This site is not directed to children under the age of 13.


Pearson may send or direct marketing communications to users, provided that

  • Pearson will not use personal information collected or processed as a K-12 school service provider for the purpose of directed or targeted advertising.
  • Such marketing is consistent with applicable law and Pearson's legal obligations.
  • Pearson will not knowingly direct or send marketing communications to an individual who has expressed a preference not to receive marketing.
  • Where required by applicable law, express or implied consent to marketing exists and has not been withdrawn.

Pearson may provide personal information to a third party service provider on a restricted basis to provide marketing solely on behalf of Pearson or an affiliate or customer for whom Pearson is a service provider. Marketing preferences may be changed at any time.

Correcting/Updating Personal Information

If a user's personally identifiable information changes (such as your postal address or email address), we provide a way to correct or update that user's personal data provided to us. This can be done on the Account page. If a user no longer desires our service and desires to delete his or her account, please contact us at customer-service@informit.com and we will process the deletion of a user's account.


Users can always make an informed choice as to whether they should proceed with certain services offered by InformIT. If you choose to remove yourself from our mailing list(s) simply visit the following page and uncheck any communication you no longer want to receive: www.informit.com/u.aspx.

Sale of Personal Information

Pearson does not rent or sell personal information in exchange for any payment of money.

While Pearson does not sell personal information, as defined in Nevada law, Nevada residents may email a request for no sale of their personal information to NevadaDesignatedRequest@pearson.com.

Supplemental Privacy Statement for California Residents

California residents should read our Supplemental privacy statement for California residents in conjunction with this Privacy Notice. The Supplemental privacy statement for California residents explains Pearson's commitment to comply with California law and applies to personal information of California residents collected in connection with this site and the Services.

Sharing and Disclosure

Pearson may disclose personal information, as follows:

  • As required by law.
  • With the consent of the individual (or their parent, if the individual is a minor)
  • In response to a subpoena, court order or legal process, to the extent permitted or required by law
  • To protect the security and safety of individuals, data, assets and systems, consistent with applicable law
  • In connection the sale, joint venture or other transfer of some or all of its company or assets, subject to the provisions of this Privacy Notice
  • To investigate or address actual or suspected fraud or other illegal activities
  • To exercise its legal rights, including enforcement of the Terms of Use for this site or another contract
  • To affiliated Pearson companies and other companies and organizations who perform work for Pearson and are obligated to protect the privacy of personal information consistent with this Privacy Notice
  • To a school, organization, company or government agency, where Pearson collects or processes the personal information in a school setting or on behalf of such organization, company or government agency.


This web site contains links to other sites. Please be aware that we are not responsible for the privacy practices of such other sites. We encourage our users to be aware when they leave our site and to read the privacy statements of each and every web site that collects Personal Information. This privacy statement applies solely to information collected by this web site.

Requests and Contact

Please contact us about this Privacy Notice or if you have any requests or questions relating to the privacy of your personal information.

Changes to this Privacy Notice

We may revise this Privacy Notice through an updated posting. We will identify the effective date of the revision in the posting. Often, updates are made to provide greater clarity or to comply with changes in regulatory requirements. If the updates involve material changes to the collection, protection, use or disclosure of Personal Information, Pearson will provide notice of the change through a conspicuous notice on this site or other appropriate way. Continued use of the site after the effective date of a posted revision evidences acceptance. Please contact us if you have questions or concerns about the Privacy Notice or any objection to any revisions.

Last Update: November 17, 2020