Created
June 26, 2018 00:37
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Demonstration of the impact of cache misses on a pic32 microcontroller. This should generate the same times on arduino, because arduino has no cache.
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| unsigned long time; | |
| const unsigned long N = 1000; | |
| int bigArr[N] = {0}; | |
| int sum; | |
| int Cache = 128; | |
| void init_arr(){ | |
| for( int i = 0; i < N; ++i){ | |
| bigArr[i] = 1; | |
| } | |
| } | |
| void setup() { | |
| Serial.begin( 9600 ); | |
| init_arr(); | |
| } | |
| void loop() { | |
| sum = 0; | |
| time = millis(); | |
| for ( int iter = 0; iter < 10000; ++iter ){ | |
| for( int i = 0; i < N; ++i ){ | |
| int idx = (i*Cache + i) % N; | |
| sum += bigArr[i]; | |
| } | |
| } | |
| time = millis() - time; | |
| Serial.print( "stride 1 time:" ); | |
| Serial.print( time ); | |
| Serial.print( " sum: " ); | |
| Serial.print( sum ); | |
| Serial.print( "\n" ); | |
| sum = 0; | |
| time = millis(); | |
| for( int iter = 0; iter < 10000; ++iter ){ | |
| for( int i = 0; i < N; ++i ){ | |
| int idx = (i*Cache + i) % N; | |
| sum += bigArr[idx]; | |
| } | |
| } | |
| time = millis() - time; | |
| Serial.print( "stride 2 time:" ); | |
| Serial.print( time ); | |
| Serial.print( " sum: " ); | |
| Serial.print( sum ); | |
| Serial.print( "\n" ); | |
| delay(N); | |
| } |
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