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1. 

   joyzhou
   Member

   Hello everyone.
   I am trying to do some FFT on maple_mini with the kiss_fft.
   The program always failes to malloc(1024*sizeof(float)),
   while the maple mini has 20KB of RAM. Why?
   Here is the code:
   

   #include <math.h>
   #include <stdlib.h>
   #include <wirish/wirish.h>
   #include "kiss_fftr.h"
   
   #define BUF_SIZE 1024
   
   void setup(void) {
   	pinMode(BOARD_LED_PIN, OUTPUT);
   	SerialUSB.begin();
   	pinMode(BOARD_BUTTON_PIN, INPUT);
   
   	while(!isButtonPressed()){
   		toggleLED();
   		delay(200);
   	}
   
   	kiss_fftr_cfg mycfg = kiss_fftr_alloc(BUF_SIZE, 0, NULL, NULL);
   	kiss_fft_scalar * rin =(kiss_fft_scalar*) malloc(BUF_SIZE * sizeof(kiss_fft_scalar));
   	kiss_fft_cpx * fout = (kiss_fft_cpx*) malloc((BUF_SIZE/2+1) * sizeof(kiss_fft_cpx));
   	if(mycfg == NULL ){
   		SerialUSB.println("mycfg failed.");
   		return;
   	}
   	if(rin == NULL){
   		SerialUSB.println("rin failed.");
   		return;
   	}
   	if(fout == NULL){
   		SerialUSB.println("fout failed.");
   		return;
   	}
   	SerialUSB.println("allocations OK.");
   
   	for(int i=0;i<BUF_SIZE;i++){
   		rin[i] = sin((float)i/20.0f) + 0.5*cos((float)i/30.0f);
   	}
   	unsigned long t0, t1;
   	t0 = micros();
   	kiss_fftr(mycfg, rin, fout);
   	t1 = micros();
   	SerialUSB.println(t1 - t0);
   	kiss_fftr_free(mycfg);
   	free(rin);
   	free(fout);
   
   }
   
   void loop(void) {
   
   	digitalWrite(BOARD_LED_PIN, HIGH);
   	delay(50);
   	digitalWrite(BOARD_LED_PIN, LOW);
   	delay(800);
   }
   
   __attribute__((constructor)) void premain() {
       init();
   }
   
   int main(void) {
       setup();
       while (true) {
           loop();
       }
       return 0;
   }

   Posted 2 years ago #
2. 

   gbulmer
   Moderator

   joyzhou - I'd suggest you make setup() simpler, and more likely to work, so that you can isolate the bug.
   For example:

   #define BUF_SIZE 10
   
   void setup(void) {
   	pinMode(BOARD_LED_PIN, OUTPUT);
   	SerialUSB.begin();
   	pinMode(BOARD_BUTTON_PIN, INPUT);
   
   	while(!isButtonPressed()){
   		toggleLED();
   		delay(200);
   	}
   
           unsigned int asize = BUF_SIZE * sizeof(kiss_fft_scalar);
           SerialUSB.print("size of allocation =");
           SerialUSB.println(asize);
   
   	kiss_fft_scalar * rin =(kiss_fft_scalar*) malloc(asize);
   
   	if(rin == NULL ){
   		SerialUSB.println("mycfg failed.");
   		return;
   	}
   }

   There are conflicting documents for malloc(), one says it doesn't work:
   http://leaflabs.com/docs/language-index.html?highlight=malloc
   and the other says it does:
   http://leaflabs.com/docs/faq.html?highlight=malloc

   I never use it, so I'm not sure which applies (I thought it did work, but I can't remember why).

   Edit: I haven't checked but I would guess at least 16KB would be free.
   It may not be working because the 'premain' initialisation might be incorrect, but I don't know that is the case. You might try a dumb program, only with setup() and loop(), using the Maple IDE to see if it makes a difference.

   (Full disclosure: I am not a member of LeafLabs staff.)

   Posted 2 years ago #
3. 

   joyzhou
   Member

   gbulmer - Thank you for the suggestions.

   I simplified the sketch.
   

   // The code(in setup):
   
           int i;
   	void * p;
   	for(i=1024;i<20*1024;i++){
   		SerialUSB.print(i);
   		p = malloc(i);
   		if(p==NULL){
   			SerialUSB.println("\t failed");
   			break;
   		}
   		else{
   			SerialUSB.println("\tOK");
   			free(p);
   		}
   	}

   The result:
   ...
   ...
   13562 OK
   13563 OK
   13564 OK
   13565 OK
   13566 failed

   That is, when a simplest program starts, there are at least 13566 bytes of *continuous* RAM. The total free RAM may be larger.

   I will modify the code to solve the problem.

   (Edit: I added code quotes to make it easier to read. I hope that is okay. gbulmer)

   Posted 2 years ago #
4. 

   gbulmer
   Moderator

   joyzhou - That's a very interesting result. Thank you for sharing.

   It's a bit disappointing, I did expect more.
   Did you try starting at too big a value? The idea is to see if the initial malloc's are fragmenting memory.

   // The code(in setup):
   
           int i;
   	void * p;
   	for(i=20*1024; i>1024;i--){
   		SerialUSB.print(i);
   		p = malloc(i);
   		if(p==NULL){
   			SerialUSB.println("\t failed");
   			continue;
   		}
   		else{
   			SerialUSB.println("\tOK");
   			free(p);
                           delay(100);
   		}
   	}

   Posted 2 years ago #

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