Simple test case to profile any speed increases that might come out of using the new dictionaryWithSharedKeySet method of creating dictionaries

ProfileSharedKeySetTests.m

//
//  ProfileSharedKeySetTests.m
//  ProfileSharedKeySetTests
//
//  Created by Marc Prud'hommeaux <mwp1@cornell.edu> on 7/16/12.
//

/**
    Simple test case to profile any speed increases that might come out of using the new dictionaryWithSharedKeySet method of creating dictionaries.
 
    For the record, on my machine (Macbook Pro Retina), I see an average speedup of 25% when using dictionaryWithSharedKeySet over normal NSMutableDictionary:
 
    keyCount=5 iterations=5000 shared=0.04 nonshared=0.05 speedup=18.10%
    keyCount=5 iterations=10000 shared=0.13 nonshared=0.15 speedup=20.20%
    keyCount=5 iterations=15000 shared=0.24 nonshared=0.29 speedup=21.19%
    keyCount=5 iterations=20000 shared=0.39 nonshared=0.46 speedup=17.74%
    keyCount=25 iterations=5000 shared=0.52 nonshared=0.62 speedup=19.25%
    keyCount=25 iterations=10000 shared=0.76 nonshared=0.95 speedup=24.25%
    keyCount=25 iterations=15000 shared=1.13 nonshared=1.43 speedup=26.94%
    keyCount=25 iterations=20000 shared=1.62 nonshared=2.06 speedup=27.49%
    keyCount=625 iterations=5000 shared=4.70 nonshared=6.20 speedup=31.93%
    keyCount=625 iterations=10000 shared=10.84 nonshared=14.28 speedup=31.75%
    keyCount=625 iterations=15000 shared=20.02 nonshared=26.23 speedup=31.01%
    keyCount=625 iterations=20000 shared=32.22 nonshared=42.41 speedup=31.63%
 
    average of speedups: 25.12% count: 12 stddev: 5.44
*/
#import "ProfileSharedKeySetTests.h"

@implementation ProfileSharedKeySetTests

/** @brief get and set keyCount keys in a shared/non-shared keySet dictionary N times and return the number of seconds it took */
- (NSTimeInterval)testShared:(BOOL)shared count:(NSUInteger)keyCount iterations:(NSUInteger)iterations {
    NSMutableArray *keys = [NSMutableArray arrayWithCapacity:keyCount];
    for (NSUInteger i = 0; i < keyCount; i++) {
        id randomKey = [[NSUUID UUID] UUIDString];
        [keys addObject:randomKey];
    }
    NSParameterAssert(keys.count == keyCount);

    id sharedKeys = shared ? [NSDictionary sharedKeySetForKeys:keys] : nil;
    
    id value = @(1); // simple value

    NSMutableDictionary *dict = sharedKeys ? [NSMutableDictionary dictionaryWithSharedKeySet:sharedKeys] : [NSMutableDictionary dictionaryWithCapacity:keyCount];

    // naïve shuffle the key array to see whether re-ordering the keys changes the performance
    [keys sortUsingComparator:^NSComparisonResult(id obj1, id obj2) {
        return arc4random() % 2 == 0 ? NSOrderedAscending : NSOrderedDescending;
    }];

    NSDate *start = [NSDate date];
    
    for (NSUInteger i = 0; i < iterations; i++) {
        for (NSUInteger k = 0; k < keyCount; k++) {
            dict[keys[k]] = value; // set
        }
        
        for (NSUInteger k = 0; k < keyCount; k++) {
            id value = dict[keys[k]]; // get
            NSParameterAssert(value);
        }
    }
    
    NSTimeInterval duration = -[start timeIntervalSinceNow];
    return duration;
}

- (void)testExample {
    NSMutableArray *speedups = [NSMutableArray array];
    for (NSUInteger keyCount = 5; keyCount <= 625; keyCount *= keyCount) {
        for (NSUInteger iterations = 5000; iterations <= 20000; iterations += 5000) {
            NSTimeInterval sharedTime, nonsharedTime;
            for (int i = 0; i < 5; i++) {
                sharedTime += [self testShared:YES count:keyCount iterations:iterations];
                nonsharedTime += [self testShared:NO count:keyCount iterations:iterations];
            }

            NSTimeInterval speedup = ((nonsharedTime - sharedTime) / sharedTime) * 100.;
            [speedups addObject:@(speedup)];
            NSLog(@"keyCount=%d iterations=%d shared=%.2f nonshared=%.2f speedup=%.2f%%", (int)keyCount, (int)iterations, (sharedTime), (nonsharedTime), speedup);
        }
    }
    
    NSArray *sups = @[[NSExpression expressionForConstantValue:speedups]];
    NSLog(@"average of speedups: %.2f%% count: %.0f stddev: %.2f",
          [[[NSExpression expressionForFunction:@"average:" arguments:sups] expressionValueWithObject:nil context:nil] doubleValue],
          [[[NSExpression expressionForFunction:@"count:" arguments:sups] expressionValueWithObject:nil context:nil] doubleValue],
          [[[NSExpression expressionForFunction:@"stddev:" arguments:sups] expressionValueWithObject:nil context:nil] doubleValue]);
}

@end