objective c - Performance issue when converting many floats to NSNumbers -

in application, i'm receiving csv file contains 30,000 objects , each object there 24 values (a total of 720,000 values).

format this:

object1,value1,value2,...,value24
object2,value1,value2,...,value24
...
objectn,value1,value2,...,value24

when parse file, convert each row in nsarray of nsstring. next following each value of array:

1. convert nsstring float using - (float)floatvalue
2. convert float nsnumber
3. store nsnumber in nsmutablearray

this process takes several seconds , instruments time profiler i'm spending 3.5 s in step 2 & 3 720,000 values.

how can proceed avoid nsnumber translation? can use c style array, []? or cfmutablearrayref? if helps, know there 24 values each object.

thanks help,

sébastien.

personally i'd use c-style array. if want process data row row, have object representing each row, this:

@interface row : nsobject {   float values[24]; } @end 

then create row instance each row, set 24 values directly, , add instance nsmutablearray.

row *row = [[[row alloc] init] autorelease]; // here's read in data row , save 24 values row.values[0] = ... ... row.values[23] = ... // , here add row instance nsmutablearray [rows addobject:row]; 

otherwise, if know front you're going expecting 30,000 rows preallocate 30,000 x 24 array of floats.

float *rows = calloc(30000*24, sizeof(float)); (int = 0; < 30000; i++) {   float *values = rows[24*i];   // here's read in data row , save 24 values   values[0] = ...   ...   values[23] = ... } 

just don't forget you'll need free memory calloc when you're done it.