CPU2017 Flag Description
Fujitsu PRIMERGY RX2520 M5, Intel Xeon Gold 5220, 2.20 GHz

Base Optimization Flags

C benchmarks

• • -xCORE-AVX2
  • 
  • COPTIMIZE

  • Code is optimized for Intel(R) processors with support for AVX2 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.

• • -ipo
  • 
  • COPTIMIZE

  • Multi-file ip optimizations that includes:
    - inline function expansion
    - interprocedural constant propogation
    - dead code elimination
    - propagation of function characteristics
    - passing arguments in registers
    - loop-invariant code motion

• • -O3
  • 
  • COPTIMIZE

  • Enables O2 optimizations plus more aggressive optimizations, such as prefetching, scalar replacement, and loop and memory access transformations. Enables optimizations for maximum speed, such as:

    • Loop unrolling, including instruction scheduling
    • Code replication to eliminate branches
    • Padding the size of certain power-of-two arrays to allow more efficient cache use.
    
    

    On IA-32 and Intel EM64T processors, when O3 is used with options -ax or -x (Linux) or with options /Qax or /Qx (Windows), the compiler performs more aggressive data dependency analysis than for O2, which may result in longer compilation times. The O3 optimizations may not cause higher performance unless loop and memory access transformations take place. The optimizations may slow down code in some cases compared to O2 optimizations. The O3 option is recommended for applications that have loops that heavily use floating-point calculations and process large data sets.

  • Includes:
    • -O2
      • -O1
        • -funroll-loops
        • -fno-builtin
        • -mno-ieee-fp
        • -fomit-framepointer
        • -ffunction-sections
        • -ftz
• • -no-prec-div
  • 
  • COPTIMIZE
  • (disable/enable[default] -prec-div)

    -no-prec-div enables optimizations that give slightly less precise results than full IEEE division.

    When you specify -no-prec-div along with some optimizations, such as -xN and -xB (Linux) or /QxN and /QxB (Windows), the compiler may change floating-point division computations into multiplication by the reciprocal of the denominator. For example, A/B is computed as A * (1/B) to improve the speed of the computation.

    However, sometimes the value produced by this transformation is not as accurate as full IEEE division. When it is important to have fully precise IEEE division, do not use -no-prec-div. This will enable the default -prec-div and the result will be more accurate, with some loss of performance.

• • -qopt-prefetch
  • 
  • COPTIMIZE

  • Enable/disable(DEFAULT) the compiler to generate prefetch instructions to prefetch data.

• • -ffinite-math-only
  • 
  • COPTIMIZE

  • Allow optimizations for floating point arithmetic that assume arguments and results are not NaNs or Infinities

• • -qopt-mem-layout-trans=3
  • 
  • COPTIMIZE

  • Controls the level of memory layout transformations performed by the compiler. This option can improve cache reuse and cache locality.

    • 0: Disables memory layout transformations. This is the same as specifying -qno-opt-mem-layout-trans
    • 1: Enables basic memory layout transformations like structure splitting, structure peeling, field inlining, field reordering, array field transpose, increase field alignment etc.
    • 2: Enables more memory layout transformations like advanced structure splitting. This is the same as specifying -qopt-mem-layout-trans
    • 3: Enables more memory layout transformations like copy-in/copy-out of structures for a region of code. You should only use this setting if your system has more than 4GB of physical memory per core.
    • 4: Compiler is more aggressive in using memory layout transformations. You should only use this setting if your system has more than 4GB of physical memory per core.

C++ benchmarks

• • -xCORE-AVX2
  • 
  • CXXOPTIMIZE

  • Code is optimized for Intel(R) processors with support for AVX2 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.

• • -ipo
  • 
  • CXXOPTIMIZE

  • Multi-file ip optimizations that includes:
    - inline function expansion
    - interprocedural constant propogation
    - dead code elimination
    - propagation of function characteristics
    - passing arguments in registers
    - loop-invariant code motion

• • -O3
  • 
  • CXXOPTIMIZE

  • Enables O2 optimizations plus more aggressive optimizations, such as prefetching, scalar replacement, and loop and memory access transformations. Enables optimizations for maximum speed, such as:

    • Loop unrolling, including instruction scheduling
    • Code replication to eliminate branches
    • Padding the size of certain power-of-two arrays to allow more efficient cache use.
    
    

    On IA-32 and Intel EM64T processors, when O3 is used with options -ax or -x (Linux) or with options /Qax or /Qx (Windows), the compiler performs more aggressive data dependency analysis than for O2, which may result in longer compilation times. The O3 optimizations may not cause higher performance unless loop and memory access transformations take place. The optimizations may slow down code in some cases compared to O2 optimizations. The O3 option is recommended for applications that have loops that heavily use floating-point calculations and process large data sets.

  • Includes:
    • -O2
      • -O1
        • -funroll-loops
        • -fno-builtin
        • -mno-ieee-fp
        • -fomit-framepointer
        • -ffunction-sections
        • -ftz
• • -no-prec-div
  • 
  • CXXOPTIMIZE
  • (disable/enable[default] -prec-div)

    -no-prec-div enables optimizations that give slightly less precise results than full IEEE division.

    When you specify -no-prec-div along with some optimizations, such as -xN and -xB (Linux) or /QxN and /QxB (Windows), the compiler may change floating-point division computations into multiplication by the reciprocal of the denominator. For example, A/B is computed as A * (1/B) to improve the speed of the computation.

    However, sometimes the value produced by this transformation is not as accurate as full IEEE division. When it is important to have fully precise IEEE division, do not use -no-prec-div. This will enable the default -prec-div and the result will be more accurate, with some loss of performance.

• • -qopt-prefetch
  • 
  • CXXOPTIMIZE

  • Enable/disable(DEFAULT) the compiler to generate prefetch instructions to prefetch data.

• • -ffinite-math-only
  • 
  • CXXOPTIMIZE

  • Allow optimizations for floating point arithmetic that assume arguments and results are not NaNs or Infinities

• • -qopt-mem-layout-trans=3
  • 
  • CXXOPTIMIZE

  • Controls the level of memory layout transformations performed by the compiler. This option can improve cache reuse and cache locality.

    • 0: Disables memory layout transformations. This is the same as specifying -qno-opt-mem-layout-trans
    • 1: Enables basic memory layout transformations like structure splitting, structure peeling, field inlining, field reordering, array field transpose, increase field alignment etc.
    • 2: Enables more memory layout transformations like advanced structure splitting. This is the same as specifying -qopt-mem-layout-trans
    • 3: Enables more memory layout transformations like copy-in/copy-out of structures for a region of code. You should only use this setting if your system has more than 4GB of physical memory per core.
    • 4: Compiler is more aggressive in using memory layout transformations. You should only use this setting if your system has more than 4GB of physical memory per core.

Fortran benchmarks

• • -xCORE-AVX2
  • 
  • FOPTIMIZE

  • Code is optimized for Intel(R) processors with support for AVX2 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.

• • -ipo
  • 
  • FOPTIMIZE

  • Multi-file ip optimizations that includes:
    - inline function expansion
    - interprocedural constant propogation
    - dead code elimination
    - propagation of function characteristics
    - passing arguments in registers
    - loop-invariant code motion

• • -O3
  • 
  • FOPTIMIZE

  • Enables O2 optimizations plus more aggressive optimizations, such as prefetching, scalar replacement, and loop and memory access transformations. Enables optimizations for maximum speed, such as:

    • Loop unrolling, including instruction scheduling
    • Code replication to eliminate branches
    • Padding the size of certain power-of-two arrays to allow more efficient cache use.
    
    

    On IA-32 and Intel EM64T processors, when O3 is used with options -ax or -x (Linux) or with options /Qax or /Qx (Windows), the compiler performs more aggressive data dependency analysis than for O2, which may result in longer compilation times. The O3 optimizations may not cause higher performance unless loop and memory access transformations take place. The optimizations may slow down code in some cases compared to O2 optimizations. The O3 option is recommended for applications that have loops that heavily use floating-point calculations and process large data sets.

  • Includes:
    • -O2
      • -O1
        • -funroll-loops
        • -fno-builtin
        • -mno-ieee-fp
        • -fomit-framepointer
        • -ffunction-sections
        • -ftz
• • -no-prec-div
  • 
  • FOPTIMIZE
  • (disable/enable[default] -prec-div)

    -no-prec-div enables optimizations that give slightly less precise results than full IEEE division.

    When you specify -no-prec-div along with some optimizations, such as -xN and -xB (Linux) or /QxN and /QxB (Windows), the compiler may change floating-point division computations into multiplication by the reciprocal of the denominator. For example, A/B is computed as A * (1/B) to improve the speed of the computation.

    However, sometimes the value produced by this transformation is not as accurate as full IEEE division. When it is important to have fully precise IEEE division, do not use -no-prec-div. This will enable the default -prec-div and the result will be more accurate, with some loss of performance.

• • -qopt-prefetch
  • 
  • FOPTIMIZE

  • Enable/disable(DEFAULT) the compiler to generate prefetch instructions to prefetch data.

• • -ffinite-math-only
  • 
  • FOPTIMIZE

  • Allow optimizations for floating point arithmetic that assume arguments and results are not NaNs or Infinities

• • -qopt-mem-layout-trans=3
  • 
  • FOPTIMIZE

  • Controls the level of memory layout transformations performed by the compiler. This option can improve cache reuse and cache locality.

    • 0: Disables memory layout transformations. This is the same as specifying -qno-opt-mem-layout-trans
    • 1: Enables basic memory layout transformations like structure splitting, structure peeling, field inlining, field reordering, array field transpose, increase field alignment etc.
    • 2: Enables more memory layout transformations like advanced structure splitting. This is the same as specifying -qopt-mem-layout-trans
    • 3: Enables more memory layout transformations like copy-in/copy-out of structures for a region of code. You should only use this setting if your system has more than 4GB of physical memory per core.
    • 4: Compiler is more aggressive in using memory layout transformations. You should only use this setting if your system has more than 4GB of physical memory per core.
• • -auto
  • 
  • FOPTIMIZE

  • Make all local variables AUTOMATIC. Same as -automatic

• • -nostandard-realloc-lhs
  • 
  • EXTRA_FOPTIMIZE

  • Option standard-realloc-lhs (the default), tells the compiler that when the left-hand side of an assignment is an allocatable object, it should be reallocated to the shape of the right-hand side of the assignment before the assignment occurs. This is the current Fortran Standard definition. This feature may cause extra overhead at run time. This option has the same effect as option assume realloc_lhs.

    If you specify nostandard-realloc-lhs, the compiler uses the old Fortran 2003 rules when interpreting assignment statements. The left-hand side is assumed to be allocated with the correct shape to hold the right-hand side. If it is not, incorrect behavior will occur. This option has the same effect as option assume norealloc_lhs.

Benchmarks using both Fortran and C

• • -xCORE-AVX2
  • 
  • COPTIMIZE, FOPTIMIZE

  • Code is optimized for Intel(R) processors with support for AVX2 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.

• • -ipo
  • 
  • COPTIMIZE, FOPTIMIZE

  • Multi-file ip optimizations that includes:
    - inline function expansion
    - interprocedural constant propogation
    - dead code elimination
    - propagation of function characteristics
    - passing arguments in registers
    - loop-invariant code motion

• • -O3
  • 
  • COPTIMIZE, FOPTIMIZE

  • Enables O2 optimizations plus more aggressive optimizations, such as prefetching, scalar replacement, and loop and memory access transformations. Enables optimizations for maximum speed, such as:

    • Loop unrolling, including instruction scheduling
    • Code replication to eliminate branches
    • Padding the size of certain power-of-two arrays to allow more efficient cache use.
    
    

    On IA-32 and Intel EM64T processors, when O3 is used with options -ax or -x (Linux) or with options /Qax or /Qx (Windows), the compiler performs more aggressive data dependency analysis than for O2, which may result in longer compilation times. The O3 optimizations may not cause higher performance unless loop and memory access transformations take place. The optimizations may slow down code in some cases compared to O2 optimizations. The O3 option is recommended for applications that have loops that heavily use floating-point calculations and process large data sets.

  • Includes:
    • -O2
      • -O1
        • -funroll-loops
        • -fno-builtin
        • -mno-ieee-fp
        • -fomit-framepointer
        • -ffunction-sections
        • -ftz
• • -no-prec-div
  • 
  • COPTIMIZE, FOPTIMIZE
  • (disable/enable[default] -prec-div)

    -no-prec-div enables optimizations that give slightly less precise results than full IEEE division.

    When you specify -no-prec-div along with some optimizations, such as -xN and -xB (Linux) or /QxN and /QxB (Windows), the compiler may change floating-point division computations into multiplication by the reciprocal of the denominator. For example, A/B is computed as A * (1/B) to improve the speed of the computation.

    However, sometimes the value produced by this transformation is not as accurate as full IEEE division. When it is important to have fully precise IEEE division, do not use -no-prec-div. This will enable the default -prec-div and the result will be more accurate, with some loss of performance.

• • -qopt-prefetch
  • 
  • COPTIMIZE, FOPTIMIZE

  • Enable/disable(DEFAULT) the compiler to generate prefetch instructions to prefetch data.

• • -ffinite-math-only
  • 
  • COPTIMIZE, FOPTIMIZE

  • Allow optimizations for floating point arithmetic that assume arguments and results are not NaNs or Infinities

• • -qopt-mem-layout-trans=3
  • 
  • COPTIMIZE, FOPTIMIZE

  • Controls the level of memory layout transformations performed by the compiler. This option can improve cache reuse and cache locality.

    • 0: Disables memory layout transformations. This is the same as specifying -qno-opt-mem-layout-trans
    • 1: Enables basic memory layout transformations like structure splitting, structure peeling, field inlining, field reordering, array field transpose, increase field alignment etc.
    • 2: Enables more memory layout transformations like advanced structure splitting. This is the same as specifying -qopt-mem-layout-trans
    • 3: Enables more memory layout transformations like copy-in/copy-out of structures for a region of code. You should only use this setting if your system has more than 4GB of physical memory per core.
    • 4: Compiler is more aggressive in using memory layout transformations. You should only use this setting if your system has more than 4GB of physical memory per core.
• • -auto
  • 
  • FOPTIMIZE

  • Make all local variables AUTOMATIC. Same as -automatic

• • -nostandard-realloc-lhs
  • 
  • EXTRA_FOPTIMIZE

  • Option standard-realloc-lhs (the default), tells the compiler that when the left-hand side of an assignment is an allocatable object, it should be reallocated to the shape of the right-hand side of the assignment before the assignment occurs. This is the current Fortran Standard definition. This feature may cause extra overhead at run time. This option has the same effect as option assume realloc_lhs.

    If you specify nostandard-realloc-lhs, the compiler uses the old Fortran 2003 rules when interpreting assignment statements. The left-hand side is assumed to be allocated with the correct shape to hold the right-hand side. If it is not, incorrect behavior will occur. This option has the same effect as option assume norealloc_lhs.

Benchmarks using both C and C++

• • -xCORE-AVX2
  • 
  • COPTIMIZE, CXXOPTIMIZE

  • Code is optimized for Intel(R) processors with support for AVX2 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.

• • -ipo
  • 
  • COPTIMIZE, CXXOPTIMIZE

  • Multi-file ip optimizations that includes:
    - inline function expansion
    - interprocedural constant propogation
    - dead code elimination
    - propagation of function characteristics
    - passing arguments in registers
    - loop-invariant code motion

• • -O3
  • 
  • COPTIMIZE, CXXOPTIMIZE

  • Enables O2 optimizations plus more aggressive optimizations, such as prefetching, scalar replacement, and loop and memory access transformations. Enables optimizations for maximum speed, such as:

    • Loop unrolling, including instruction scheduling
    • Code replication to eliminate branches
    • Padding the size of certain power-of-two arrays to allow more efficient cache use.
    
    

    On IA-32 and Intel EM64T processors, when O3 is used with options -ax or -x (Linux) or with options /Qax or /Qx (Windows), the compiler performs more aggressive data dependency analysis than for O2, which may result in longer compilation times. The O3 optimizations may not cause higher performance unless loop and memory access transformations take place. The optimizations may slow down code in some cases compared to O2 optimizations. The O3 option is recommended for applications that have loops that heavily use floating-point calculations and process large data sets.

  • Includes:
    • -O2
      • -O1
        • -funroll-loops
        • -fno-builtin
        • -mno-ieee-fp
        • -fomit-framepointer
        • -ffunction-sections
        • -ftz
• • -no-prec-div
  • 
  • COPTIMIZE, CXXOPTIMIZE
  • (disable/enable[default] -prec-div)

    -no-prec-div enables optimizations that give slightly less precise results than full IEEE division.

    When you specify -no-prec-div along with some optimizations, such as -xN and -xB (Linux) or /QxN and /QxB (Windows), the compiler may change floating-point division computations into multiplication by the reciprocal of the denominator. For example, A/B is computed as A * (1/B) to improve the speed of the computation.

    However, sometimes the value produced by this transformation is not as accurate as full IEEE division. When it is important to have fully precise IEEE division, do not use -no-prec-div. This will enable the default -prec-div and the result will be more accurate, with some loss of performance.

• • -qopt-prefetch
  • 
  • COPTIMIZE, CXXOPTIMIZE

  • Enable/disable(DEFAULT) the compiler to generate prefetch instructions to prefetch data.

• • -ffinite-math-only
  • 
  • COPTIMIZE, CXXOPTIMIZE

  • Allow optimizations for floating point arithmetic that assume arguments and results are not NaNs or Infinities

• • -qopt-mem-layout-trans=3
  • 
  • COPTIMIZE, CXXOPTIMIZE

  • Controls the level of memory layout transformations performed by the compiler. This option can improve cache reuse and cache locality.

    • 0: Disables memory layout transformations. This is the same as specifying -qno-opt-mem-layout-trans
    • 1: Enables basic memory layout transformations like structure splitting, structure peeling, field inlining, field reordering, array field transpose, increase field alignment etc.
    • 2: Enables more memory layout transformations like advanced structure splitting. This is the same as specifying -qopt-mem-layout-trans
    • 3: Enables more memory layout transformations like copy-in/copy-out of structures for a region of code. You should only use this setting if your system has more than 4GB of physical memory per core.
    • 4: Compiler is more aggressive in using memory layout transformations. You should only use this setting if your system has more than 4GB of physical memory per core.

Benchmarks using Fortran, C, and C++

• • -xCORE-AVX2
  • 
  • COPTIMIZE, CXXOPTIMIZE, FOPTIMIZE

  • Code is optimized for Intel(R) processors with support for AVX2 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.

• • -ipo
  • 
  • COPTIMIZE, CXXOPTIMIZE, FOPTIMIZE

  • Multi-file ip optimizations that includes:
    - inline function expansion
    - interprocedural constant propogation
    - dead code elimination
    - propagation of function characteristics
    - passing arguments in registers
    - loop-invariant code motion

• • -O3
  • 
  • COPTIMIZE, CXXOPTIMIZE, FOPTIMIZE

  • Enables O2 optimizations plus more aggressive optimizations, such as prefetching, scalar replacement, and loop and memory access transformations. Enables optimizations for maximum speed, such as:

    • Loop unrolling, including instruction scheduling
    • Code replication to eliminate branches
    • Padding the size of certain power-of-two arrays to allow more efficient cache use.
    
    

    On IA-32 and Intel EM64T processors, when O3 is used with options -ax or -x (Linux) or with options /Qax or /Qx (Windows), the compiler performs more aggressive data dependency analysis than for O2, which may result in longer compilation times. The O3 optimizations may not cause higher performance unless loop and memory access transformations take place. The optimizations may slow down code in some cases compared to O2 optimizations. The O3 option is recommended for applications that have loops that heavily use floating-point calculations and process large data sets.

  • Includes:
    • -O2
      • -O1
        • -funroll-loops
        • -fno-builtin
        • -mno-ieee-fp
        • -fomit-framepointer
        • -ffunction-sections
        • -ftz
• • -no-prec-div
  • 
  • COPTIMIZE, CXXOPTIMIZE, FOPTIMIZE
  • (disable/enable[default] -prec-div)

    -no-prec-div enables optimizations that give slightly less precise results than full IEEE division.

    When you specify -no-prec-div along with some optimizations, such as -xN and -xB (Linux) or /QxN and /QxB (Windows), the compiler may change floating-point division computations into multiplication by the reciprocal of the denominator. For example, A/B is computed as A * (1/B) to improve the speed of the computation.

    However, sometimes the value produced by this transformation is not as accurate as full IEEE division. When it is important to have fully precise IEEE division, do not use -no-prec-div. This will enable the default -prec-div and the result will be more accurate, with some loss of performance.

• • -qopt-prefetch
  • 
  • COPTIMIZE, CXXOPTIMIZE, FOPTIMIZE

  • Enable/disable(DEFAULT) the compiler to generate prefetch instructions to prefetch data.

• • -ffinite-math-only
  • 
  • COPTIMIZE, CXXOPTIMIZE, FOPTIMIZE

  • Allow optimizations for floating point arithmetic that assume arguments and results are not NaNs or Infinities

• • -qopt-mem-layout-trans=3
  • 
  • COPTIMIZE, CXXOPTIMIZE, FOPTIMIZE

  • Controls the level of memory layout transformations performed by the compiler. This option can improve cache reuse and cache locality.

    • 0: Disables memory layout transformations. This is the same as specifying -qno-opt-mem-layout-trans
    • 1: Enables basic memory layout transformations like structure splitting, structure peeling, field inlining, field reordering, array field transpose, increase field alignment etc.
    • 2: Enables more memory layout transformations like advanced structure splitting. This is the same as specifying -qopt-mem-layout-trans
    • 3: Enables more memory layout transformations like copy-in/copy-out of structures for a region of code. You should only use this setting if your system has more than 4GB of physical memory per core.
    • 4: Compiler is more aggressive in using memory layout transformations. You should only use this setting if your system has more than 4GB of physical memory per core.
• • -auto
  • 
  • FOPTIMIZE

  • Make all local variables AUTOMATIC. Same as -automatic

• • -nostandard-realloc-lhs
  • 
  • EXTRA_FOPTIMIZE

  • Option standard-realloc-lhs (the default), tells the compiler that when the left-hand side of an assignment is an allocatable object, it should be reallocated to the shape of the right-hand side of the assignment before the assignment occurs. This is the current Fortran Standard definition. This feature may cause extra overhead at run time. This option has the same effect as option assume realloc_lhs.

    If you specify nostandard-realloc-lhs, the compiler uses the old Fortran 2003 rules when interpreting assignment statements. The left-hand side is assumed to be allocated with the correct shape to hold the right-hand side. If it is not, incorrect behavior will occur. This option has the same effect as option assume norealloc_lhs.