Compilers: Intel c/c++/fortran Compiler 18.0.0.082
Operating systems: Linux
Last updated: 06-Nov-2017 blw
Selecting one of the following will take you directly to that section:
Enable OpenMP.
Specifies the memory model for the compiled binary object as 32-bit.'
Specifies the memory model for the compiled binary object as 64-bit.'
Enables OpenMP* offloading compilation for target pragmas. This
option only applies to Intel(R) MIC Architecture and Intel(R)
Graphics Technology. Enabled by default with -qopenmp.
Use -qno-openmp-offload to disable.
Specify kind to specify the default device for target pragmas
host - allow target code to run on host system while still doing
the outlining for offload
mic - specify Intel(R) MIC Architecture
gfx - specify Intel(R) Graphics Technology
Enables OpenMP support.
Enable Debug output. Generate an optimization report to stderr
Enable levels of prefetch insertion, where 0 disables. n may be 0 through 4 inclusive. Default is 2.
Defines the accuracy (precision) for math library functions
This option improves precision of square root implementations. It has a slight impact on speed.
Improve precision of FP divides (some speed impact)
Specifies whether streaming stores are generated always - enables generation of streaming stores under the assumption that the application is memory bound auto - compiler decides when streaming stores are used (DEFAULT) never - disables generation of streaming stores
Produce symbolic debug information in object file (implies -O0 when another optimization option is not explicitly set)
May generate Intel(R) Advanced Vector Extensions 2 (Intel(R) AVX2), Intel(R) AVX, SSE4.2, SSE4.1, SSSE3, SSE3, SSE2, and SSE instructions for Intel(R) processors. Optimizes for a future Intel processor.
May generate Intel(R) Advanced Vector Extensions 2 (Intel(R) AVX2), Intel(R) AVX, SSE4.2, SSE4.1, SSSE3, SSE3, SSE2, and SSE instructions for Intel(R) MICs. Optimizes for a future Intel processor.
May generate Intel(R) Advanced Vector Extensions (Intel(R) AVX), Intel(R) SSE4.2, SSE4.1, SSSE3, SSE3, SSE2, and SSE instructions for Intel(R) processors. Optimizes for a future Intel processor.
Specify how data items are aligned.
This options tells the compiler to assume no aliasing in the program.
Specify malloc configuration parameters. Specifying a non-zero value will cause alternate configuration parameters to be set for how malloc allocates and frees memory
enable
[no-]except - enable/disable floating point semantics
fast[=1|2] - enables more aggressive floating point optimizations
precise - allows value-safe optimizations
source - enables intermediates in source precision
strict - enables -fp-model precise -fp-model except, disables
contractions and enables pragma stdc fenv_access
double - rounds intermediates in 53-bit (double) precision
extended - rounds intermediates in 64-bit (extended) precision
Enable/disable(DEFAULT) calls to fast calloc function
Code is optimized for Intel(R) processors with support for SSE 4.2 instructions. The resulting code may contain unconditional use of features that are not supported on other processors. This option also enables new optimizations in addition to Intel processor-specific optimizations including advanced data layout and code restructuring optimizations to improve memory accesses for Intel processors.
Do not use this option if you are executing a program on a processor that is not an Intel processor. If you use this option on a non-compatible processor to compile the main program (in Fortran) or the function main() in C/C++, the program will display a fatal run-time error if they are executed on unsupported processors.
Specifies whether streaming stores are generated:
always - enables generation of streaming stores under the assumption that the application is memory bound
auto - compiler decides when streaming stores are used (DEFAULT)
never - disables generation of streaming stores
Enable use of ANSI aliasing rules optimizations; user asserts that the program adheres to these rules
Enable multi-file IP optimization between files
Adds the directory for include files to the search path at compile time.
Adds the directory for include files to the search path at compile time.
Adds the library directory search path at link time
Enables support for Offload.
Enables support of AVX2.
Specify optimization level n:
-mcmodel=
Specify rightmost column for fixed form sources
Specify C standard
No Fortran main method exists, use C equivalent instead.
Link MKL (Intel Math Kernel Libraries).
Specify source files are in free format.
Code for Xeon Phi (ManyCore) enabled, GPU specific code disabled.
Enables the use of nested SIMD statements for OpenMP.
Link using FFTW 3.3.6 library for Linux. Description from FFTW:
FFTW is a C subroutine library for computing the discrete Fourier transform (DFT) in one or more dimensions, of arbitrary input size, and of both real and complex data (as well as of even/odd data, i.e. the discrete cosine/sine transforms or DCT/DST).
KMP_AFFINITY
The KMP_AFFINITY environment variable uses the following general syntax:
Syntax |
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KMP_AFFINITY=[<modifier>,...]<type>[,<permute>][,<offset>] |
For example, to list a machine topology map, specify KMP_AFFINITY=verbose,none to use a modifier of verbose and a type of none.
The following table describes the supported specific arguments.
| Argument |
Default |
Description |
|---|---|---|
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noverbose respect granularity=core |
Optional. String consisting of keyword and specifier.
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none |
Required string. Indicates the thread affinity to use.
The logical and physical types are deprecated but supported for backward compatibility. |
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0 |
Optional. Positive integer value. Not valid with type values of explicit, none, or disabled. | |
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0 |
Optional. Positive integer value. Not valid with type values of explicit, none, or disabled. |
Type is the only required argument.
Does not bind OpenMP threads to particular thread contexts; however, if the operating system supports affinity, the compiler still uses the OpenMP thread affinity interface to determine machine topology. Specify KMP_AFFINITY=verbose,none to list a machine topology map.
Specifying compact assigns the OpenMP thread <n>+1 to a free thread context as close as possible to the thread context where the <n> OpenMP thread was placed. For example, in a topology map, the nearer a node is to the root, the more significance the node has when sorting the threads.
Specifying disabled completely disables the thread affinity interfaces. This forces the OpenMP run-time library to behave as if the affinity interface was not supported by the operating system. This includes the low-level API interfaces such as kmp_set_affinity and kmp_get_affinity, which have no effect and will return a nonzero error code.
Specifying explicit assigns OpenMP threads to a list of OS proc IDs that have been explicitly specified by using the proclist= modifier, which is required for this affinity type.
Specifying scatter distributes the threads as evenly as possible across the entire system. scatter is the opposite of compact; so the leaves of the node are most significant when sorting through the machine topology map.
Types logical and physical are deprecated and may become unsupported in a future release. Both are supported for backward compatibility.
For logical and physical affinity types, a single trailing integer is interpreted as an offset specifier instead of a permute specifier. In contrast, with compact and scatter types, a single trailing integer is interpreted as a permute specifier.
Specifying logical assigns OpenMP threads to consecutive logical processors, which are also called hardware thread contexts. The type is equivalent to compact, except that the permute specifier is not allowed. Thus, KMP_AFFINITY=logical,n is equivalent to KMP_AFFINITY=compact,0,n (this equivalence is true regardless of the whether or not a granularity=fine modifier is present).
For both compact and scatter, permute and offset are allowed; however, if you specify only one integer, the compiler interprets the value as a permute specifier. Both permute and offset default to 0.
The permute specifier controls which levels are most significant when sorting the machine topology map. A value for permute forces the mappings to make the specified number of most significant levels of the sort the least significant, and it inverts the order of significance. The root node of the tree is not considered a separate level for the sort operations.
The offset specifier indicates the starting position for thread assignment.
Modifiers are optional arguments that precede type. If you do not specify a modifier, the noverbose, respect, and granularity=core modifiers are used automatically.
Modifiers are interpreted in order from left to right, and can negate each other. For example, specifying KMP_AFFINITY=verbose,noverbose,scatter is therefore equivalent to setting KMP_AFFINITY=noverbose,scatter, or just KMP_AFFINITY=scatter.
Does not print verbose messages.
Prints messages concerning the supported affinity. The messages include information about the number of packages, number of cores in each package, number of thread contexts for each core, and OpenMP thread bindings to physical thread contexts.
Information about binding OpenMP threads to physical thread contexts is indirectly shown in the form of the mappings between hardware thread contexts and the operating system (OS) processor (proc) IDs. The affinity mask for each OpenMP thread is printed as a set of OS processor IDs.
KMP_LIBRARY
KMP_LIBRARY = [ throughput | turnaround | serial ], Selects the OpenMP run-time library execution mode. The options for the variable value are throughput, turnaround, and serial.
The compiler with OpenMP enables you to run an application under different execution modes that can be specified at run time. The libraries support the serial, turnaround, and throughput modes.
The serial mode forces parallel applications to run on a single processor.
In a dedicated (batch or single user) parallel environment where all processors are exclusively allocated to the program for its entire run, it is most important to effectively utilize all of the processors all of the time. The turnaround mode is designed to keep active all of the processors involved in the parallel computation in order to minimize the execution time of a single job. In this mode, the worker threads actively wait for more parallel work, without yielding to other threads.
Avoid over-allocating system resources. This occurs if either too many threads have been specified, or if too few processors are available at run time. If system resources are over-allocated, this mode will cause poor performance. The throughput mode should be used instead if this occurs.
In a multi-user environment where the load on the parallel machine is not constant or where the job stream is not predictable, it may be better to design and tune for throughput. This minimizes the total time to run multiple jobs simultaneously. In this mode, the worker threads will yield to other threads while waiting for more parallel work.
The throughput mode is designed to make the program aware of its environment (that is, the system load) and to adjust its resource usage to produce efficient execution in a dynamic environment. This mode is the default.
KMP_BLOCKTIME
KMP_BLOCKTIME = value. Sets the time, in milliseconds, that a thread should wait, after completing the execution of a parallel region, before sleeping.Use the optional character suffixes: s (seconds), m (minutes), h (hours), or d (days) to specify the units.Specify infinite for an unlimited wait time.
KMP_STACKSIZE
KMP_STACKSIZE = value. Sets the number of bytes to allocate for each OpenMP* thread to use as the private stack for the thread. Recommended size is 16m. Use the optional suffixes: b (bytes), k (kilobytes), m (megabytes), g (gigabytes), or t (terabytes) to specify the units. This variable does not affect the native operating system threads created by the user program nor the thread executing the sequential part of an OpenMP* program or parallel programs created using -parallel.
OMP_NUM_THREADS
Sets the maximum number of threads to use for OpenMP* parallel regions if no other value is specified in the application. This environment variable applies to both -openmp and -parallel. Example syntax on a Linux system with 8 cores: export OMP_NUM_THREADS=8
OMP_DYNAMIC
OMP_DYNAMIC=[ 1 | 0 ] Enables (1) or disables (0) the dynamic adjustment of the number of threads.
OMP_NESTED
OMP_DYNAMIC=[ TRUE | FALSE ] The OMP_NESTED environment variable enables or disables nested parallelism unless nested parallelism is enabled or disabled by calling the omp_set_nested library routine. If set to TRUE, nested parallelism is enabled; if it is set to FALSE, nested parallelism is disabled. The default value is FALSE.