ACCEL Flag Description
Supermicro A+ Server 1023US-TR4

Test sponsored by NVIDIA Corporation

Implicitly Included Flags

This section contains descriptions of flags that were included implicitly by other flags, but which do not have a permanent home at SPEC.

• • -O2
  • 
  • pgcc_l, pgcpp_l, pgcplusplus_l, pgf90_l, pgf95_l, pgfortran_l, pgcc_w, pgcpp_w, pgf90_w, pgf95_w, pgfortran_w

  • Level-two optimization (-O2 or -O) specifies global optimization. The -fast option generally will specify global optimization; however, the -fast switch will vary from release to release depending on a reasonable selection of switches for any one particular release. The -O or -O2 level performs all level-one local optimizations as well as global optimizations. Control flow analysis is applied and global registers are allocated for all functions and subroutines. Loop regions are given special consideration. This optimization level is a good choice when the program contains loops, the loops are short, and the structure of the code is regular.

    The PGI compilers perform many different types of global optimizations, including but not limited to:

    • Branch to branch elimination
    • Constant propagation
    • Copy propagation
    • Dead store elimination
    • Global register allocation
    • Invariant code motion
    • Induction variable elimination
  • Includes:
    • -O1
• • -O1
  • 
  • pgcc_l, pgcpp_l, pgcplusplus_l, pgf90_l, pgf95_l, pgfortran_l, pgcc_w, pgcpp_w, pgf90_w, pgf95_w, pgfortran_w

  • Level-one optimization specifies local optimization (-O1). The compiler performs scheduling of basic blocks as well as register allocation. This optimization level is a good choice when the code is very irregular; that is it contains many short statements containing IF statements and the program does not contain loops (DO or DO WHILE statements). For certain types of code, this optimization level may perform better than level-two (-O2) although this case rarely occurs.

    The PGI compilers perform many different types of local optimizations, including but not limited to:

    • Algebraic identity removal
    • Constant folding
    • Common subexpression elimination
    • Local register optimization
    • Peephole optimizations
    • Redundant load and store elimination
    • Strength reductions
    Note that this is the default optimiation level when no optimization flags are specified on the compilation command line.
• • -Munroll=c:1
  • 
  • pgcc_l, pgcpp_l, pgcplusplus_l, pgf90_l, pgf95_l, pgfortran_l, pgcc_w, pgcpp_w, pgf90_w, pgf95_w, pgfortran_w

  • Instructs the compiler to completely unroll loops with a constant loop count of less than or equal to 1 where 1 is a supplied constant value. If no constant value is given, then a default of 4 is used. A value of 1 inhibits the complete unrolling of loops with constant loop counts.

  • Includes:
    • -Munroll
• • -Munroll
  • 
  • pgcc_l, pgcpp_l, pgcplusplus_l, pgf90_l, pgf95_l, pgfortran_l, pgcc_w, pgcpp_w, pgf90_w, pgf95_w, pgfortran_w

  • Invokes the loop unroller.

• • -Mautoinline
  • 
  • pgcc_l, pgcpp_l, pgcplusplus_l, pgf90_l, pgf95_l, pgfortran_l, pgcc_w, pgcpp_w, pgf90_w, pgf95_w, pgfortran_w

  • Inline functions declared with the inline keyword.

• • -Msmart
  • 
  • pgcc_l, pgcpp_l, pgcplusplus_l, pgf90_l, pgf95_l, pgfortran_l, pgcc_w, pgcpp_w, pgf90_w, pgf95_w, pgfortran_w

  • Enable an optional post-pass instruction scheduling.

• • -Mlre
  • 
  • pgcc_l, pgcpp_l, pgcplusplus_l, pgf90_l, pgf95_l, pgfortran_l, pgcc_w, pgcpp_w, pgf90_w, pgf95_w, pgfortran_w

  • Enables loop-carried redundancy elimination, an optimization that can reduce the number of arithmetic operations and memory references in loops.

• • -Mnoframe
  • 
  • pgcc_l, pgcpp_l, pgcplusplus_l, pgf90_l, pgf95_l, pgfortran_l, pgcc_w, pgcpp_w, pgf90_w, pgf95_w, pgfortran_w

  • Eliminates operations that set up a true stack frame pointer for every function. With this option enabled, you cannot perform a traceback on the generated code and you cannot access local variables.

• • -Mvect=sse
  • 
  • pgcc_l, pgcpp_l, pgcplusplus_l, pgf90_l, pgf95_l, pgfortran_l, pgcc_w, pgcpp_w, pgf90_w, pgf95_w, pgfortran_w

  • Instructs the vectorizer to search for vectorizable loops and, where possible, make use of SSE, SSE2, and prefetch instructions.

  • Includes:
    • -Mvect
      • -Mvect=assoc
      • -Mvect=altcode
• • -Mvect
  • 
  • pgcc_l, pgcpp_l, pgcplusplus_l, pgf90_l, pgf95_l, pgfortran_l, pgcc_w, pgcpp_w, pgf90_w, pgf95_w, pgfortran_w

  • Enable automatic vector pipelining.

  • Includes:
    • -Mvect=assoc
    • -Mvect=altcode
• • -Mvect=assoc
  • 
  • pgcc_l, pgcpp_l, pgcplusplus_l, pgf90_l, pgf95_l, pgfortran_l, pgcc_w, pgcpp_w, pgf90_w, pgf95_w, pgfortran_w

  • Instructs the vectorizer to enable certain associativity conversions that can change the results of a computations due to roundoff error. A typical optimization is to change an arithmetic operation to an arithmetic opteration that is mathmatically correct, but can be computationally different, due to round-off error.

• • -Mvect=altcode
  • 
  • pgcc_l, pgcpp_l, pgcplusplus_l, pgf90_l, pgf95_l, pgfortran_l, pgcc_w, pgcpp_w, pgf90_w, pgf95_w, pgfortran_w

  • Instructs the vectorizer to generate alternate code for vectorized loops when appropriate. For each vectorized loop the compiler decides whether to generate altcode and what type or types to generate, which may be any or all of:

    • Altcode without iteration peeling
    • Altcode with non-temporal stores and other data cache optimizations
    • Altcode base on array alignments calculated dynamically at runtime.

    The compiler also determines suitable loop count and array alignment conditions for executing the altcode.

• • -Mcache_align
  • 
  • pgcc_l, pgcpp_l, pgcplusplus_l, pgf90_l, pgf95_l, pgfortran_l, pgcc_w, pgcpp_w, pgf90_w, pgf95_w, pgfortran_w

  • Align "unconstrained" data objects of size greater than or equal to 16 bytes on cache-line boundaries. An "unconstrained" object is a variable or array that is not a member of an aggregate structure or common block, is not allocatable, and is not an automatic array. On by default on 64-bit Linux systems.

• • -Mflushz
  • 
  • pgcc_l, pgcpp_l, pgcplusplus_l, pgf90_l, pgf95_l, pgfortran_l, pgcc_w, pgcpp_w, pgf90_w, pgf95_w, pgfortran_w

  • Set SSE to flush-to-zero mode; if a floating-point underflow occurs, the value is set to zero.

• • -Mdaz
  • 
  • pgcc_l, pgcpp_l, pgcplusplus_l, pgf90_l, pgf95_l, pgfortran_l, pgcc_w, pgcpp_w, pgf90_w, pgf95_w, pgfortran_w

  • Treat denormalized numbers as zero. Included with "-fast" on Intel based systems. For AMD based systems, "-Mdaz" is not included by default with "-fast".

• • -Mscalarsse
  • 
  • pgcc_l, pgcpp_l, pgcplusplus_l, pgf90_l, pgf95_l, pgfortran_l, pgcc_w, pgcpp_w, pgf90_w, pgf95_w, pgfortran_w

  • Use SSE/SSE2 instructions to perform scalar floating-point arithmetic on targets where these instructions are supported. This option is default on SSE2 enabled target architectures.

Shell, Environment, and Other Software Settings

Shell, Environment, and Other Software Settings - All compiler versions

Set stack size to unlimited

The command "ulimit -s unlimited" is used to set the stack size limit to unlimited.

numactl --interleave=all "runspec command"

Launching a process with numactl --interleave=all sets the memory interleave policy so that memory will be allocated using round robin on nodes. When memory cannot be allocated on the current interleave target fall back to other nodes.

OMP_NUM_THREADS

Sets the maximum number of threads to use for OpenMP parallel regions if no other value is specified in the application. Example syntax on a Linux system with 8 cores: export OMP_NUM_THREADS=8

OMP_STACKSIZE

Specify stack size to be allocated for each thread.

ACC_NUM_CORES

Sets the maximum number of CPU cores to use. Default is to use all available physical cores.

HUGETLB_PATH

Set the huge TLB pages mount path.

Shell, Environment, and Other Software Settings - PGI LLVM Compiler - x86 and Power architectures.

OMP_PROC_BIND

If set to 'true', bind CPU threads to cores. Default is 'false'.

OMP_PLACES

Set the thread to core number binding.

Example: OMP_PLACES={0},{1},{2},{3}

KMP_AFFINITY

Syntax: KMP_AFFINITY=[<modifier>,...]<type>[,<permute>][,<offset>]
The value for the environment variable KMP_AFFINITY affects how the threads from an auto-parallelized program are scheduled across processors.
It applies to binaries built with -mp using the PGI LLVM compilers on x86 and Power.
modifier:
    granularity=fine Causes each OpenMP thread to be bound to a single thread context.
type:
    compact 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.
    scatter Specifying scatter distributes the threads as evenly as possible across the entire system.
permute: The permute specifier is an integer value 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.
offset: The offset specifier indicates the starting position for thread assignment.

Example: KMP_AFFINITY=granularity=fine,scatter
Specifying granularity=fine selects the finest granularity level and causes each OpenMP or auto-par thread to be bound to a single thread context.
This ensures that there is only one thread per core on cores supporting HyperThreading Technology
Specifying scatter distributes the threads as evenly as possible across the entire system.
Hence a combination of these two options, will spread the threads evenly across sockets, with one thread per physical core.

Example: KMP_AFFINITY=compact,1,0
Specifying compact will assign the n+1 thread to a free thread context as close as possible to thread n.
A default granularity=core is implied if no granularity is explicitly specified.
Specifying 1,0 sets permute and offset values of the thread assignment.
With a permute value of 1, thread n+1 is assigned to a consecutive core. With an offset of 0, the process's first thread 0 will be assigned to thread 0.
The same behavior is exhibited in a multisocket system.

Shell, Environment, and Other Software Settings - PGI Native x86 compilers

MP_BIND

If set to 'yes', bind CPU threads to cores. Default is 'no'.

MP_BLIST

Set the thread to core number binding.

Example: MP_BIND=0,1,2,3

MP_SPIN

Specifies the number of times to check a semaphore before calling sched_yield() (on Linux or macOS) or _sleep() (on Windows).

Flag description origin markings:

	Indicates that the flag description came from the user flags file.
	Indicates that the flag description came from the suite-wide flags file.
	Indicates that the flag description came from a per-benchmark flags file.

For questions about the meanings of these flags, please contact the tester.
For other inquiries, please contact webmaster@spec.org
Copyright 2015-2018 Standard Performance Evaluation Corporation
Tested with SPEC ACCEL v1.2.
Report generated on Thu Aug 30 18:55:33 2018 by SPEC ACCEL flags formatter v1290.