80 lines
2.2 KiB
Python
80 lines
2.2 KiB
Python
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blocks = [100,500,200,400, 300]
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processes = [110,50,410]
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def firstfit():
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block1= blocks.copy()
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for p in processes:
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for b in block1:
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if b>=p:
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print(f"P {p} allocated to B {b}")
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block1.pop(block1.index(b))
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break
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else: print(f"P {p} not allocated")
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print(f"Blocks empty: ", block1)
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print(blocks,"\n",processes)
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print("\n\n FF:")
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firstfit()
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def bestfit():
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block1= sorted(blocks)
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for p in processes:
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for b in block1:
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if b>=p:
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print(f"P {p} allocated to B {b}")
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block1.pop(block1.index(b))
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break
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else: print(f"P {p} not allocated")
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print(f"Blocks empty: ", block1)
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print("\n\n BF:")
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bestfit()
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'''
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Common External Q: why tha fuck was worst fit even invented?
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->coz in bestfit, we have small spaces left in all the blocks.unuseable.
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But in worstfit, we have one large space in the biggest block. so we can put in one more process if extra.
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This is called External Fragmentation...
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so, Worstfit is better than Bestfit
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Answer by Afan Shaikh'''
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def worstfit():
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block1= sorted(blocks, reverse=True)
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for p in processes:
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for b in block1:
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if b>=p:
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print(f"P {p} allocated to B {b}")
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block1.pop(block1.index(b))
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break
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else: print(f"P {p} not allocated")
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print(f"Blocks empty: ", block1)
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print("\n\n WF:")
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worstfit()
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'''
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NF:
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You need to know working of NF, before understanding it's code.
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start is the starting index for current iteration. at end, we do start++
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the ind= i%n wraps the index around, like a circle.
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After allocation, I make block=0 to mark allocated. Who tf is gonna cross check?
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'''
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def nextfit():
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start = 0
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n = len(blocks)
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for p in processes:
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for i in range(start, start +n):
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ind = i % n
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if blocks[ind] >= p:
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print(f"P {p} allocated to B {blocks[ind]}")
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blocks[ind] = 0
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start = (ind +1 ) % n
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break
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else: print(f'P {p} not allocated')
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a=[x for x in blocks if x>0]
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print("Blocks empty: ", a)
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print("\n\n NF:")
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nextfit()
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