printing floating point

portion of my code:

--- Quote Start ---

dma_tick = (unsigned int)(end_dma - start_dma);

pio_tick = (unsigned int)(end_pio - start_pio);

freq = (unsigned int)(alt_timestamp_freq());

improve = (((pio_tick - dma_tick)/pio_tick) *100);

printf("Printing report..\n\n");

printf("******* System Performance Analysis *******\n");

printf("Data size tested : %d Bytes\n", (length*4));

printf("Number of ticks per second : %u\n", freq);

printf("Without DMA: Number of ticks: %u\n", pio_tick);

printf("DMA: Number of ticks : %u\n", dma_tick);

printf("* System Performance Improvement: %lf\n", improve);

--- Quote End ---

i cant print improve...

i am using full lib, not small or reduced..