pm_arrayReverse Module Reference

This module contains procedures and generic interfaces for reversing the order of elements in arrays of various types. More...

Data Types
interface	getReversed
	Generate and return an output array whose elements are the reversed-order elements of the input array, such that   array = array(lenArray:1:-1),   where lenArray = len(array) if array is a scalar character, or lenArray = size(array) is an array of rank 1. More...
interface	setReversed
	Reverse the order of the elements of the input array, such that   array = array(lenArray:1:-1),   where lenArray = len(array) if array is a scalar character, or lenArray = size(array) is an array of rank 1. More...

Variables
character(*, SK), parameter	MODULE_NAME = "@pm_arrayReverse"

Detailed Description

This module contains procedures and generic interfaces for reversing the order of elements in arrays of various types.

Benchmarks:

Benchmark :: The runtime performance of setReversed vs. direct reversing ⛓

! Test the performance of `getReversed()` vs. `setReversed()`.
program benchmark
 
    use iso_fortran_env, only: error_unit
    use pm_arrayResize, only: setResized
    use pm_distUnif, only: getUnifRand
    use pm_bench, only: bench_type
    use pm_kind, only: IK, RK, SK
 
    implicit none
 
    integer(IK)                         :: i
    integer(IK)                         :: isize
    integer(IK)                         :: fileUnit
    integer(IK) , parameter             :: nsize = 11_IK
    integer(IK) , parameter             :: NBENCH = 3_IK
    integer(IK)                         :: arraySize(nsize)
    real(RK)                            :: dummySum = 0._RK
    real(RK)    , allocatable           :: array(:), arrayReverse(:)
    type(bench_type)                    :: bench(NBENCH)
 
    bench(1) = bench_type(name = SK_"getReversed", exec = getReversed, overhead = setOverhead)
    bench(2) = bench_type(name = SK_"setReversed", exec = setReversed, overhead = setOverhead)
    bench(3) = bench_type(name = SK_"setReversed_overwrite", exec = setReversed_overwrite , overhead = setOverhead)
 
    arraySize = [( 2_IK**isize, isize = 1_IK, nsize )]
 
    write(*,"(*(g0,:,' '))")
    write(*,"(*(g0,:,' '))") "getReversed() vs. setReversed() vs. setReversed_overwrite()"
    write(*,"(*(g0,:,' '))")
 
    open(newunit = fileUnit, file = "main.out", status = "replace")
 
        write(fileUnit, "(*(g0,:,','))") "arraySize", (bench(i)%name, i = 1, NBENCH)
 
        loopOverArraySize: do isize = 1, nsize
 
            array = getUnifRand(1_IK, 9_IK, arraySize(isize))
            call setResized(arrayReverse, arraySize(isize))
            write(*,"(*(g0,:,' '))") "Benchmarking with rank", arraySize(isize)
 
            do i = 1, NBENCH
                bench(i)%timing = bench(i)%getTiming(minsec = 0.05_RK)
            end do
 
            write(fileUnit,"(*(g0,:,','))") arraySize(isize), (bench(i)%timing%mean, i = 1, NBENCH)
 
        end do loopOverArraySize
        write(*,"(*(g0,:,' '))") dummySum
        write(*,"(*(g0,:,' '))")
 
    close(fileUnit)
 
contains
 
    !%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
    ! procedure wrappers.
    !%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 
    subroutine setOverhead()
        call getDummy()
    end subroutine
 
    subroutine getDummy()
        dummySum = dummySum + sum(array)
    end subroutine
 
    subroutine getReversed()
        block
            use pm_arrayReverse, only: getReversed
            arrayReverse = getReversed(array)
            call getDummy()
        end block
    end subroutine
 
    subroutine setReversed()
        block
            use pm_arrayReverse, only: setReversed
            call setReversed(array, arrayReverse)
            call getDummy()
        end block
    end subroutine
 
    subroutine setReversed_overwrite()
        block
            use pm_arrayReverse, only: setReversed
            call setReversed(array)
            call getDummy()
        end block
    end subroutine
 
end program benchmark

Example Unix compile command via Intel ifort compiler ⛓

#!/usr/bin/env sh
rm main.exe
ifort -fpp -standard-semantics -O3 -Wl,-rpath,../../../lib -I../../../inc main.F90 ../../../lib/libparamonte* -o main.exe
./main.exe

Example Windows Batch compile command via Intel ifort compiler ⛓

del main.exe
set PATH=..\..\..\lib;%PATH%
ifort /fpp /standard-semantics /O3 /I:..\..\..\include main.F90 ..\..\..\lib\libparamonte*.lib /exe:main.exe
main.exe

Example Unix / MinGW compile command via GNU gfortran compiler ⛓

#!/usr/bin/env sh
rm main.exe
gfortran -cpp -ffree-line-length-none -O3 -Wl,-rpath,../../../lib -I../../../inc main.F90 ../../../lib/libparamonte* -o main.exe
./main.exe

Postprocessing of the benchmark output ⛓

#!/usr/bin/env python
 
import matplotlib.pyplot as plt
import pandas as pd
import numpy as np
 
fontsize = 14
 
methods = ["setReversed_overwrite", "setReversed", "getReversed"]
 
df = pd.read_csv("main.out")
 
 
 
ax = plt.figure(figsize = 1.25 * np.array([6.4,4.6]), dpi = 200)
ax = plt.subplot()
 
for method in methods:
    plt.plot( df["arraySize"].values
            , df[method].values
            , linewidth = 2
            )
 
plt.xticks(fontsize = fontsize)
plt.yticks(fontsize = fontsize)
ax.set_xlabel("Array Size", fontsize = fontsize)
ax.set_ylabel("Runtime [ seconds ]", fontsize = fontsize)
ax.set_title("getReversed() vs. setReversed() vs. setReversed_overwrite()\nLower is better.", fontsize = fontsize)
ax.set_xscale("log")
ax.set_yscale("log")
plt.minorticks_on()
plt.grid(visible = True, which = "both", axis = "both", color = "0.85", linestyle = "-")
ax.tick_params(axis = "y", which = "minor")
ax.tick_params(axis = "x", which = "minor")
ax.legend   ( methods
           #, loc='center left'
           #, bbox_to_anchor=(1, 0.5)
            , fontsize = fontsize
            )
 
plt.tight_layout()
plt.savefig("benchmark.getReversed_vs_setReversed.runtime.png")
 
 
 
ax = plt.figure(figsize = 1.25 * np.array([6.4,4.6]), dpi = 200)
ax = plt.subplot()
 
plt.plot( df["arraySize"].values
        , np.ones(len(df["arraySize"].values))
       #, linestyle = "--"
       #, color = "black"
        , linewidth = 2
        )
plt.plot( df["arraySize"].values
        , df["setReversed"].values / df["setReversed_overwrite"].values
        , linewidth = 2
        )
plt.plot( df["arraySize"].values
        , df["getReversed"].values / df["setReversed_overwrite"].values
        , linewidth = 2
        )
 
plt.xticks(fontsize = fontsize)
plt.yticks(fontsize = fontsize)
ax.set_xlabel("Array Size", fontsize = fontsize)
ax.set_ylabel("Runtime compared to setReversed_overwrite()", fontsize = fontsize)
ax.set_title("getReversed / setReversed_overwrite vs. setReversed / setReversed_overwrite\nLower means faster. Lower than 1 means faster than setReversed_overwrite().", fontsize = fontsize)
ax.set_xscale("log")
#ax.set_yscale("log")
plt.minorticks_on()
plt.grid(visible = True, which = "both", axis = "both", color = "0.85", linestyle = "-")
ax.tick_params(axis = "y", which = "minor")
ax.tick_params(axis = "x", which = "minor")
ax.legend   ( ["setReversed_overwrite", "setReversed", "getReversed"]
           #, bbox_to_anchor = (1, 0.5)
           #, loc = "center left"
            , fontsize = fontsize
            )
 
plt.tight_layout()
plt.savefig("benchmark.getReversed_vs_setReversed.runtime.ratio.png")

Visualization of the benchmark output ⛓

Benchmark moral ⛓

1. The procedures under the generic interface setReversed with in-place array reversal (corresponding to setReversed_overwrite() in the benchmark) tend to be significantly faster than the functional-interface procedures getReversed.
   The reason is likely the extra copy required with the functional interface.

Test:

test_pm_arrayReverse

Final Remarks ⛓

---

If you believe this algorithm or its documentation can be improved, we appreciate your contribution and help to edit this page's documentation and source file on GitHub.
For details on the naming abbreviations, see this page.
For details on the naming conventions, see this page.
This software is distributed under the MIT license with additional terms outlined below.

1. If you use any parts or concepts from this library to any extent, please acknowledge the usage by citing the relevant publications of the ParaMonte library.
   
2. If you regenerate any parts/ideas from this library in a programming environment other than those currently supported by this ParaMonte library (i.e., other than C, C++, Fortran, MATLAB, Python, R), please also ask the end users to cite this original ParaMonte library.
   

This software is available to the public under a highly permissive license.
Help us justify its continued development and maintenance by acknowledging its benefit to society, distributing it, and contributing to it.

Copyright

Computational Data Science Lab

Author:

Fatemeh Bagheri, Wednesday 12:20 AM, October 13, 2021, Dallas, TX

Variable Documentation

MODULE_NAME

character(*, SK), parameter pm_arrayReverse::MODULE_NAME = "@pm_arrayReverse"

Definition at line 49 of file pm_arrayReverse.F90.