Nested Sweep Area - Modern Fortran Programming

Nested loops evaluate every pair from two parameter lists and keep the best combination.
Program

Play the program to include more width choices in the sweep.
                            width_count
                            width_count = 2 (default)width_count = 1width_count = 3
                        

                            nested_sweep_area.f90
                        
Replay: real traced execution (multi-file project)

                            program nested_sweep_area_demo
    implicit none
    integer :: widths(3)
    integer :: heights(2)
    integer :: width_count
    integer :: height_count
    integer :: wi, hi
    integer :: width, height, area
    integer :: best_width, best_height, best_area

    widths = [2, 4, 6]
    heights = [3, 5]
    width_count = 2
    height_count = 2
    best_area = -1
    best_width = 0
    best_height = 0
    do wi = 1, width_count
        width = widths(wi)
        do hi = 1, height_count
            height = heights(hi)
            area = width * height
            if (area > best_area) then
                best_area = area
                best_width = width
                best_height = height
            end if
        end do
    end do
    print '(I0, 1X, I0, 1X, I0)', best_width, best_height, best_area
end program nested_sweep_area_demo
program nested_sweep_area_demo
    implicit none
    integer :: widths(3)
    integer :: heights(2)
    integer :: width_count
    integer :: height_count
    integer :: wi, hi
    integer :: width, height, area
    integer :: best_width, best_height, best_area

    widths = [2, 4, 6]
    heights = [3, 5]
    width_count = 1
    height_count = 2
    best_area = -1
    best_width = 0
    best_height = 0
    do wi = 1, width_count
        width = widths(wi)
        do hi = 1, height_count
            height = heights(hi)
            area = width * height
            if (area > best_area) then
                best_area = area
                best_width = width
                best_height = height
            end if
        end do
    end do
    print '(I0, 1X, I0, 1X, I0)', best_width, best_height, best_area
end program nested_sweep_area_demo
program nested_sweep_area_demo
    implicit none
    integer :: widths(3)
    integer :: heights(2)
    integer :: width_count
    integer :: height_count
    integer :: wi, hi
    integer :: width, height, area
    integer :: best_width, best_height, best_area

    widths = [2, 4, 6]
    heights = [3, 5]
    width_count = 3
    height_count = 2
    best_area = -1
    best_width = 0
    best_height = 0
    do wi = 1, width_count
        width = widths(wi)
        do hi = 1, height_count
            height = heights(hi)
            area = width * height
            if (area > best_area) then
                best_area = area
                best_width = width
                best_height = height
            end if
        end do
    end do
    print '(I0, 1X, I0, 1X, I0)', best_width, best_height, best_area
end program nested_sweep_area_demo

                        
1widths ← [2, 4, 6]⋯11widths = [2, 4, 6]12heights = [3, 5]⋯values this step[2, 4, 6]widths
2heights ← [3, 5]⋯11widths = [2, 4, 6]12heights = [3, 5]13width_count = 2⋯values this step[3, 5]heights
3width_count ← 2⋯12heights = [3, 5]13width_count = 214height_count = 2⋯values this step2width_count
4height_count ← 2⋯13width_count = 214height_count = 215best_area = -1⋯values this step2height_count
5best_area ← -1⋯14height_count = 215best_area = -116best_width = 0⋯values this step-1best_area
6best_width ← 0⋯15best_area = -116best_width = 017best_height = 0⋯values this step0best_width
7best_height ← 0⋯16best_width = 017best_height = 018do wi = 1, width_count⋯values this step0best_height
8wi ← 1⋯17best_height = 018do wi = 1, width_count19    width = widths(wi)⋯values this step1wi
9width ← 2⋯18do wi = 1, width_count19    width = widths(wi)20    do hi = 1, height_count⋯values this step2width
10hi ← 1⋯19width = widths(wi)20do hi = 1, height_count21    height = heights(hi)⋯values this step1hi
11height ← 3⋯20do hi = 1, height_count21    height = heights(hi)22    area = width * height⋯values this step3height
12area ← 6⋯21height = heights(hi)22area = width * height23if (area > best_area) then⋯values this step6area2width3height
13if (area > best_area) then⋯22area = width * height23if (area > best_area) then24    best_area = area⋯values this step.true.area > best_area
14best_area ← 6⋯23if (area > best_area) then24    best_area = area25    best_width = width⋯values this step6best_area
15best_width ← 2⋯24best_area = area25best_width = width26best_height = height⋯values this step2best_width
16best_height ← 3⋯25    best_width = width26    best_height = height27end if⋯values this step3best_height
17hi ← 2⋯19width = widths(wi)20do hi = 1, height_count21    height = heights(hi)⋯values this step2hi
18height ← 5⋯20do hi = 1, height_count21    height = heights(hi)22    area = width * height⋯values this step5height
19area ← 10⋯21height = heights(hi)22area = width * height23if (area > best_area) then⋯values this step10area2width5height
20if (area > best_area) then⋯22area = width * height23if (area > best_area) then24    best_area = area⋯values this step.true.area > best_area
21best_area ← 10⋯23if (area > best_area) then24    best_area = area25    best_width = width⋯values this step10best_area
22best_width ← 2⋯24best_area = area25best_width = width26best_height = height⋯values this step2best_width
23best_height ← 5⋯25    best_width = width26    best_height = height27end if⋯values this step5best_height
24wi ← 2⋯17best_height = 018do wi = 1, width_count19    width = widths(wi)⋯values this step2wi
25width ← 4⋯18do wi = 1, width_count19    width = widths(wi)20    do hi = 1, height_count⋯values this step4width
26hi ← 1⋯19width = widths(wi)20do hi = 1, height_count21    height = heights(hi)⋯values this step1hi
27height ← 3⋯20do hi = 1, height_count21    height = heights(hi)22    area = width * height⋯values this step3height
28area ← 12⋯21height = heights(hi)22area = width * height23if (area > best_area) then⋯values this step12area4width3height
29if (area > best_area) then⋯22area = width * height23if (area > best_area) then24    best_area = area⋯values this step.true.area > best_area
30best_area ← 12⋯23if (area > best_area) then24    best_area = area25    best_width = width⋯values this step12best_area
31best_width ← 4⋯24best_area = area25best_width = width26best_height = height⋯values this step4best_width
32best_height ← 3⋯25    best_width = width26    best_height = height27end if⋯values this step3best_height
33hi ← 2⋯19width = widths(wi)20do hi = 1, height_count21    height = heights(hi)⋯values this step2hi
34height ← 5⋯20do hi = 1, height_count21    height = heights(hi)22    area = width * height⋯values this step5height
35area ← 20⋯21height = heights(hi)22area = width * height23if (area > best_area) then⋯values this step20area4width5height
36if (area > best_area) then⋯22area = width * height23if (area > best_area) then24    best_area = area⋯values this step.true.area > best_area
37best_area ← 20⋯23if (area > best_area) then24    best_area = area25    best_width = width⋯values this step20best_area
38best_width ← 4⋯24best_area = area25best_width = width26best_height = height⋯values this step4best_width
39best_height ← 5⋯25    best_width = width26    best_height = height27end if⋯values this step5best_height
40print '(I0, 1X, I0, 1X, I0)', best_width, best_height, best_area⋯29    end do30    print '(I0, 1X, I0, 1X, I0)', best_width, best_height, best_area31end program nested_sweep_area_demooutput4 5 20values this step4best_width5best_height20best_area
1widths ← [2, 4, 6]⋯11widths = [2, 4, 6]12heights = [3, 5]⋯values this step[2, 4, 6]widths
2heights ← [3, 5]⋯11widths = [2, 4, 6]12heights = [3, 5]13width_count = 1⋯values this step[3, 5]heights
3width_count ← 1⋯12heights = [3, 5]13width_count = 114height_count = 2⋯values this step1width_count
4height_count ← 2⋯13width_count = 114height_count = 215best_area = -1⋯values this step2height_count
5best_area ← -1⋯14height_count = 215best_area = -116best_width = 0⋯values this step-1best_area
6best_width ← 0⋯15best_area = -116best_width = 017best_height = 0⋯values this step0best_width
7best_height ← 0⋯16best_width = 017best_height = 018do wi = 1, width_count⋯values this step0best_height
8wi ← 1⋯17best_height = 018do wi = 1, width_count19    width = widths(wi)⋯values this step1wi
9width ← 2⋯18do wi = 1, width_count19    width = widths(wi)20    do hi = 1, height_count⋯values this step2width
10hi ← 1⋯19width = widths(wi)20do hi = 1, height_count21    height = heights(hi)⋯values this step1hi
11height ← 3⋯20do hi = 1, height_count21    height = heights(hi)22    area = width * height⋯values this step3height
12area ← 6⋯21height = heights(hi)22area = width * height23if (area > best_area) then⋯values this step6area2width3height
13if (area > best_area) then⋯22area = width * height23if (area > best_area) then24    best_area = area⋯values this step.true.area > best_area
14best_area ← 6⋯23if (area > best_area) then24    best_area = area25    best_width = width⋯values this step6best_area
15best_width ← 2⋯24best_area = area25best_width = width26best_height = height⋯values this step2best_width
16best_height ← 3⋯25    best_width = width26    best_height = height27end if⋯values this step3best_height
17hi ← 2⋯19width = widths(wi)20do hi = 1, height_count21    height = heights(hi)⋯values this step2hi
18height ← 5⋯20do hi = 1, height_count21    height = heights(hi)22    area = width * height⋯values this step5height
19area ← 10⋯21height = heights(hi)22area = width * height23if (area > best_area) then⋯values this step10area2width5height
20if (area > best_area) then⋯22area = width * height23if (area > best_area) then24    best_area = area⋯values this step.true.area > best_area
21best_area ← 10⋯23if (area > best_area) then24    best_area = area25    best_width = width⋯values this step10best_area
22best_width ← 2⋯24best_area = area25best_width = width26best_height = height⋯values this step2best_width
23best_height ← 5⋯25    best_width = width26    best_height = height27end if⋯values this step5best_height
24print '(I0, 1X, I0, 1X, I0)', best_width, best_height, best_area⋯29    end do30    print '(I0, 1X, I0, 1X, I0)', best_width, best_height, best_area31end program nested_sweep_area_demooutput2 5 10values this step2best_width5best_height10best_area
1widths ← [2, 4, 6]⋯11widths = [2, 4, 6]12heights = [3, 5]⋯values this step[2, 4, 6]widths
2heights ← [3, 5]⋯11widths = [2, 4, 6]12heights = [3, 5]13width_count = 3⋯values this step[3, 5]heights
3width_count ← 3⋯12heights = [3, 5]13width_count = 314height_count = 2⋯values this step3width_count
4height_count ← 2⋯13width_count = 314height_count = 215best_area = -1⋯values this step2height_count
5best_area ← -1⋯14height_count = 215best_area = -116best_width = 0⋯values this step-1best_area
6best_width ← 0⋯15best_area = -116best_width = 017best_height = 0⋯values this step0best_width
7best_height ← 0⋯16best_width = 017best_height = 018do wi = 1, width_count⋯values this step0best_height
8wi ← 1⋯17best_height = 018do wi = 1, width_count19    width = widths(wi)⋯values this step1wi
9width ← 2⋯18do wi = 1, width_count19    width = widths(wi)20    do hi = 1, height_count⋯values this step2width
10hi ← 1⋯19width = widths(wi)20do hi = 1, height_count21    height = heights(hi)⋯values this step1hi
11height ← 3⋯20do hi = 1, height_count21    height = heights(hi)22    area = width * height⋯values this step3height
12area ← 6⋯21height = heights(hi)22area = width * height23if (area > best_area) then⋯values this step6area2width3height
13if (area > best_area) then⋯22area = width * height23if (area > best_area) then24    best_area = area⋯values this step.true.area > best_area
14best_area ← 6⋯23if (area > best_area) then24    best_area = area25    best_width = width⋯values this step6best_area
15best_width ← 2⋯24best_area = area25best_width = width26best_height = height⋯values this step2best_width
16best_height ← 3⋯25    best_width = width26    best_height = height27end if⋯values this step3best_height
17hi ← 2⋯19width = widths(wi)20do hi = 1, height_count21    height = heights(hi)⋯values this step2hi
18height ← 5⋯20do hi = 1, height_count21    height = heights(hi)22    area = width * height⋯values this step5height
19area ← 10⋯21height = heights(hi)22area = width * height23if (area > best_area) then⋯values this step10area2width5height
20if (area > best_area) then⋯22area = width * height23if (area > best_area) then24    best_area = area⋯values this step.true.area > best_area
21best_area ← 10⋯23if (area > best_area) then24    best_area = area25    best_width = width⋯values this step10best_area
22best_width ← 2⋯24best_area = area25best_width = width26best_height = height⋯values this step2best_width
23best_height ← 5⋯25    best_width = width26    best_height = height27end if⋯values this step5best_height
24wi ← 2⋯17best_height = 018do wi = 1, width_count19    width = widths(wi)⋯values this step2wi
25width ← 4⋯18do wi = 1, width_count19    width = widths(wi)20    do hi = 1, height_count⋯values this step4width
26hi ← 1⋯19width = widths(wi)20do hi = 1, height_count21    height = heights(hi)⋯values this step1hi
27height ← 3⋯20do hi = 1, height_count21    height = heights(hi)22    area = width * height⋯values this step3height
28area ← 12⋯21height = heights(hi)22area = width * height23if (area > best_area) then⋯values this step12area4width3height
29if (area > best_area) then⋯22area = width * height23if (area > best_area) then24    best_area = area⋯values this step.true.area > best_area
30best_area ← 12⋯23if (area > best_area) then24    best_area = area25    best_width = width⋯values this step12best_area
31best_width ← 4⋯24best_area = area25best_width = width26best_height = height⋯values this step4best_width
32best_height ← 3⋯25    best_width = width26    best_height = height27end if⋯values this step3best_height
33hi ← 2⋯19width = widths(wi)20do hi = 1, height_count21    height = heights(hi)⋯values this step2hi
34height ← 5⋯20do hi = 1, height_count21    height = heights(hi)22    area = width * height⋯values this step5height
35area ← 20⋯21height = heights(hi)22area = width * height23if (area > best_area) then⋯values this step20area4width5height
36if (area > best_area) then⋯22area = width * height23if (area > best_area) then24    best_area = area⋯values this step.true.area > best_area
37best_area ← 20⋯23if (area > best_area) then24    best_area = area25    best_width = width⋯values this step20best_area
38best_width ← 4⋯24best_area = area25best_width = width26best_height = height⋯values this step4best_width
39best_height ← 5⋯25    best_width = width26    best_height = height27end if⋯values this step5best_height
40wi ← 3⋯17best_height = 018do wi = 1, width_count19    width = widths(wi)⋯values this step3wi
41width ← 6⋯18do wi = 1, width_count19    width = widths(wi)20    do hi = 1, height_count⋯values this step6width
42hi ← 1⋯19width = widths(wi)20do hi = 1, height_count21    height = heights(hi)⋯values this step1hi
43height ← 3⋯20do hi = 1, height_count21    height = heights(hi)22    area = width * height⋯values this step3height
44area ← 18⋯21height = heights(hi)22area = width * height23if (area > best_area) then⋯values this step18area6width3height
45if (area > best_area) then⋯22area = width * height23if (area > best_area) then24    best_area = area⋯values this step.false.area > best_area
46hi ← 2⋯19width = widths(wi)20do hi = 1, height_count21    height = heights(hi)⋯values this step2hi
47height ← 5⋯20do hi = 1, height_count21    height = heights(hi)22    area = width * height⋯values this step5height
48area ← 30⋯21height = heights(hi)22area = width * height23if (area > best_area) then⋯values this step30area6width5height
49if (area > best_area) then⋯22area = width * height23if (area > best_area) then24    best_area = area⋯values this step.true.area > best_area
50best_area ← 30⋯23if (area > best_area) then24    best_area = area25    best_width = width⋯values this step30best_area
51best_width ← 6⋯24best_area = area25best_width = width26best_height = height⋯values this step6best_width
52best_height ← 5⋯25    best_width = width26    best_height = height27end if⋯values this step5best_height
53print '(I0, 1X, I0, 1X, I0)', best_width, best_height, best_area⋯29    end do30    print '(I0, 1X, I0, 1X, I0)', best_width, best_height, best_area31end program nested_sweep_area_demooutput6 5 30values this step6best_width5best_height30best_area
nested loop The outer loop picks one width and the inner loop tries every height.
combination Each `(width, height)` pair is one sweep case.
best combination The current best parameter pair is updated when its area is larger.