Fix WMath's map() implementation for inverse/round-trip mapping#7027
Merged
earlephilhower merged 2 commits intoesp8266:masterfrom Feb 9, 2020
Merged
Fix WMath's map() implementation for inverse/round-trip mapping#7027earlephilhower merged 2 commits intoesp8266:masterfrom
earlephilhower merged 2 commits intoesp8266:masterfrom
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Contributor
Author
|
Here's the sketch for testing correctness and timing: uint32_t expired;
uint32_t iterations;
void setup()
{
Serial.begin(115200);
while (!Serial);
Serial.println("check map");
expired = 0;
iterations = 0;
}
constexpr int imin = 0;
constexpr int imax = 180;
constexpr int omin = 1000;
constexpr int omax = 2000;
int i = 0;
int fails = 0;
void loop()
{
++iterations;
i = (i + 1) % (imax + 1);
#if defined(ESP8266) || defined(ESP32)
cli();
volatile auto start = ESP.getCycleCount();
#else
// Set Timer 1 to normal mode at F_CPU.
TCCR1A = 0;
TCCR1B = 1;
cli();
volatile uint16_t start = TCNT1;
#endif
volatile auto o = map(i, imin, imax, omin, omax);
#if defined(ESP8266) || defined(ESP32)
sei();
volatile auto cycles = ESP.getCycleCount() - start;
#else
sei();
volatile uint16_t finish = TCNT1;
uint16_t cycles = finish - start;
#endif
expired += cycles;
if (i != map(o, omin, omax, imin, imax))
{
++fails;
}
if (iterations > 100000)
{
Serial.print("Cycles per map(...) = "); Serial.print(expired / iterations);
Serial.print(", fails = "); Serial.print(fails);
Serial.println();
expired = 0;
iterations = 0;
fails = 0;
}
} |
Contributor
Author
…ion. Greatly reduces error rate (half, or 0 zero errors, depends on in/out ranges) for round-trip mapping at the same performance.
devyte
reviewed
Feb 9, 2020
| const long divisor = in_max - in_min; | ||
| const long delta = x - in_min; | ||
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| return (delta * dividend + (divisor / 2)) / divisor + out_min; |
Collaborator
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This doesn't handle divisor == 0.
Contributor
Author
|
This today got merged into Arduino Core for ESP32, espressif/arduino-esp32#3655 |
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Inspired by Servo.cpp's
improved_map, this superseded that code, and has better performance (identical to prior WMath implementation).I expect this is better used to replace the core implementation, then drop "improved_map" from Servo.cpp, than keep it local and have a map() function that may be compatible but works horribly ;-)